Дисертації: "Steel Hydrogen embrittlement Testing"

1

Brahimi, Salim. "Effect of surface processing variables on hydrogen embrittlement of steel fasteners." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112560.

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Incremental step load testing was used in accordance with ASTM F1940 to rank a number coating processes used in the fastener industry for their propensity to cause internal hydrogen embrittlement. The results showed that coating permeability has a first order effect, while the quantity of hydrogen introduced by the process has a second order effect. Pure zinc electroplating processes, alkaline and acid, were found to be the most embrittling, owing to the low permeability of zinc. The least embrittling processes were zinc-nickel, alkaline and acid, owing to the high permeability of Zn-Ni coatings. Non-electrolytic processes, namely phosphating, mechanical galvanising, DacrometRTM and Magni 555RTM were found to be non-embrittling. Hot dip galvanising was found to be highly embrittling, evidently due to trapped hydrogen being released by the thermal shock of up-quenching upon immersion in molten zinc. The full effect of up-quenching on the metallurgical and mechanical properties of high strength steel requires further investigation.

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2

Bromley, Darren Michael. "Hydrogen embrittlement testing of austenitic stainless steels SUS 316 and 316L." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/925.

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The imminent emergence of the hydrogen fuel industry has resulted in an urgent mandate for very specific material testing. Although storage of pressurized hydrogen gas is both practical and attainable, demands for increasing storage pressures (currently around 70 MPa) continue to present unexpected material compatibility issues. It is imperative that materials commonly used in gaseous hydrogen service are properly tested for hydrogen embrittlement resistance. To assess material behavior in a pressurized hydrogen environment, procedures were designed to test materials for susceptibility to hydrogen embrittlement. Of particular interest to the field of high-pressure hydrogen in the automotive industry, austenitic stainless steels SUS 316 and 316L were used to validate the test programs. Tests were first performed in 25 MPa helium and hydrogen at room temperature and at -40°C. Tests in a 25 MPa hydrogen atmosphere caused embrittlement in SUS 316, but not in 316L. This indicated that alloys with higher stacking fault energies (316L) are more resistant to hydrogen embrittlement. Decreasing the test temperature caused slight embrittlement in 316L and significantly enhanced it in 316. Alternatively, a second set of specimens was immersed in 70 MPa hydrogen at 100°C until reaching a uniform concentration of absorbed hydrogen. Specimens were then loaded in tension to failure to determine if a bulk saturation of hydrogen provided a similar embrittling effect. Neither material succumbed to the effects of gaseous pre-charging, indicating that the embrittling mechanism requires a constant supply of hydrogen at the material surface rather than having bulk concentration of dissolved hydrogen. Permeation tests were also performed to ensure that hydrogen penetrated the samples and to develop material specific permeation constants. To pave the way for future work, prototype equipment was constructed allowing tensile or fatigue tests to be performed at much higher hydrogen pressures. To determine the effect of pressure on hydrogen embrittlement, additional tests can be performed in hydrogen pressures up to 85 MPa hydrogen. The equipment will also allow for cyclic loading of notched tensile or compact tension specimens for fatigue studies.

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3

Li, Xuan. "Hydrogen Effects on X80 Steel Mechanical Properties Measured by Tensile and Impact Testing." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6110.

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The effect of hydrogen charging current density and tensile strain rate on the mechanical properties of X80 pipeline steel were investigated by slow strain rate test (SSRT), Charpy impact test, and scanning electron microscopy (SEM) in this thesis. The results show that both the ultimate tensile strength and elongation to failure of X80 steel were deteriorated significantly after charging with hydrogen. With a strain rate of 5 x 10-5 s-1, the relative tensile strength and plasticity loss of X80 steel had no significant change within the range of assumed hydrogen partial pressures at room temperature. At room temperature, X80 steel had no apparent variation in ultimate tensile strength and elongation, except at the strain rate of 10-6 s-1. Specimens obtained the greatest relative tensile strength loss and plasticity loss when strained at 10-6 s-1 with a current density of 4.6 mA/cm2. The fracture morphology of two test groups of X80 steel exhibited significant brittle rupture when tested with dynamic hydrogen charging. The impact energy of X80 was not affected by hydrogen charging. Different current density also had no influence on the results of the impact test.

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4

Tohme, Elia. "A contribution to the understanding of hydrogen diffusion and embrittlement in metallic materials based on SKPFM measurements and mechanical testing." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEM025.

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Cette étude contribue à une meilleure compréhension du phénomène de fragilisation par l’hydrogène des aciers.la première partie du manuscrit est consacrée à l'évaluation d'une méthode récemment développée pour étudier la diffusion de l'hydrogène, basée sur la détection de la variation du travail de sortie en surface par microscopie à force atomique et sonde de kelvin (skpfm). un acier inoxydable duplex a été utilisé, les deux phases ayant chacune des caractéristiques liées à l’hydrogène (diffusivité, solubilité) différentes. une couche de palladium a été déposée sur la surface d’observation qui se comporte comme un collecteur d’hydrogène. une simulation par éléments finis de la diffusion d’hydrogène dans un système multiphasé a été développée afin d’interpréter les observations expérimentales. il est démontré que la technique de skpfm doit être considérée comme un moyen de suivre localement la désorption de l’hydrogène dans la couche de pd, plutôt qu’un moyen de cartographier la concentration en hydrogène dans la microstructure du matériau.la deuxième partie traite de la fph d'un acier maraging sous chargement cathodique au regard des propriétés de diffusion et de piégeage de l'hydrogène. des essais mécaniques dynamiques et statiques ont été utilisés, tandis que différentes conditions d’entrée d’hydrogène ont été explorées : chargement cathodique direct de l’hydrogène ou, via un trajet de diffusion dans le matériau en protégeant la pointe de l’entaille de l’environnement. l’amorçage de la fissure dépend du transport de l'hydrogène par diffusion accélérée selon des chemins préférentiels. un régime sous-critique de propagation de fissure est identifié. il correspond à un mode de fissuration mixte inter/transgranulaire, le mode ig faisant référence aux anciens joints de grain gamma et le mode tg à des interfaces de fortes désorientations. cette étape est dépendante de la diffusion de l’hydrogène; elle correspond à des vitesses de propagation de fissure relativement stable en fonction du facteur d'intensité des contraintes
This study contributes to a better understanding of the hydrogen embrittlement phenomenon of steels.the first part of this manuscript is devoted to the assessment of a recently developed method to study hydrogen diffusion based on the detection of the variation of the work function of the surface by scanning kelvin probe microscopy (skpfm). a duplex stainless steel was used in this study, due to its two different phases having different hydrogen-related characteristics (diffusivity, solubility). a palladium layer was deposited on the observation surface and behaved as a hydrogen collector. a finite element simulation of hydrogen diffusion in a multiphase system was developed to explain the experimental observations. it is shown that skpfm should be considered as a way to monitor locally the release of hydrogen into the palladium layer, rather than a way to map the hydrogen concentration in the material microstructure.the second part of the manuscript deals with the hydrogen embrittlement of a maraging steel under cathodic charging with regard to hydrogen diffusion and trapping properties. dynamic and static mechanical testing were used, while various conditions of hydrogen ingress were explored corresponding to a direct cathodic hydrogen charging, or via a diffusion path in the material by protecting the notch tip from the environment. crack initiation stage is dependent on the hydrogen transport, and accumulation, by accelerated diffusion along preferential paths. a sub-critical regime of crack propagation is identified. it corresponds to a mixed intergranular/transgranular mode of cracking, the ig mode referring to prior gamma-grain boundaries and tg mode to high-angle misorientation interfaces of the martensite. this stage is hydrogen diffusion-dependent; it corresponds to a steady state crack growth rate vs stress intensity factor. the final fracture at a critical kih value is dependent on hydrogen content in the material and refers to tg mode of cracking

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5

Santos, Luis Paulo MourÃo dos. "AvaliaÃÃo da fragilizaÃÃo por hidrogÃnio no aÃo maraging 300." Universidade Federal do CearÃ, 2014. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=12599.

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CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior
Os aÃos maraging sÃo ligas de ultra-alta resistÃncia com vasta aplicaÃÃo na engenharia, desde vasos de alta pressÃo de operaÃÃo em processos crÃticos, componentes aeronÃuticos, aplicaÃÃes militares atÃ equipamentos esportivos. O presente trabalho buscou avaliar os efeitos da fragilizaÃÃo por hidrogÃnio no aÃo maraging 18% Ni da classe 300, nas condiÃÃes solubilizada e envelhecida. As amostras foram solubilizadas a 1093 Â10K por 3,6 ks, seguido de um resfriamento ao ar e envelhecidas a 753 e 843 Â10K por 10,8 ks, respectivamente e resfriadas ao ar. Foi realizada uma caracterizaÃÃo microestrutural por difraÃÃo de raios-X, correntes parasitas, medidas de dureza Rockwell e microscopia eletrÃnica e Ãptica. Para avaliar os efeitos do ingresso de hidrogÃnio nas propriedades mecÃnicas do aÃo maraging 18% Ni da classe 300 foram realizados ensaios de traÃÃo com baixa taxa de deformaÃÃo (BTD). A taxa de deformaÃÃo aplicada foi 1,0 x 10-6 s-1. Os ensaios foram realizados ao ar (meio inerte) e em soluÃÃo de 3,5% NaCl sob o potencial catÃdico de -1,2 VECS. Foi observada uma reduÃÃo de 11,06 para 3,89% no alongamento e de 61,28 para 10% na reduÃÃo de Ãrea para as amostras solubilizadas. As amostras envelhecidas a 753 Â10K por 10.8 ks apresentaram maior reduÃÃo nessas propriedades. Nesta condiÃÃo a reduÃÃo observada foi de 1929,26 MPa para amostras ensaiadas ao ar para 447,64 MPa para amostras ensaiadas em soluÃÃo de 3,5% NaCl sob potencial catÃdico no limite de resistÃncia e de 7,30 para 1,62 % no alongamento. As amostras envelhecidas a 843 Â10K, as quais apresentaram de cerca de 10% de austenita sofreram fragilizaÃÃo similar as amostras envelhecidas a 753 Â10K. Trincas secundÃrias perpendiculares a carga aplicada foram observadas nas amostras solubilizadas e ensaiadas em soluÃÃo de 3,5% NaCl sob potencial catÃdico. Os resultados indicam que a presenÃa de precipitados e de austenita revertida impedem a propagaÃÃo de trincas secundÃrias na seÃÃo longitudinal nas condiÃÃes envelhecidas. A anÃlise da superfÃcie de fratura revelou caracterÃstica de uma fratura dÃctil nas amostras ensaiadas ao ar com dimples de diferentes tamanhos e profundidades, enquanto que nas amostras ensaiadas em soluÃÃo de 3,5% NaCl sob potencial catÃdico foram observadas trincas induzidas pelo hidrogÃnio e microcavidades e regiÃes de quase-clivagem para todas as condiÃÃes estudadas.
Maraging steels are ultra high strength alloys widely used in engineering applications from high pressure vessels operating in critical processes, aircraft components, military applications to sports equipment. This work assessed the effects of hydrogen embrittlement in 18% Ni maraging grade 300 steel in the solution annealed and aged conditions. Samples were solution annealed at 1093 Â10K for 3.6 ks, followed by air cooling and aging at 753 and 843 Â10K for 10.8 ks, respectively, and cooled by air. The microstructure was characterized by X-ray diffraction, eddy current, hardness measurement and optical and electron microscopy. To assess the effects of hydrogen ingress on the mechanical properties of 18% Ni maraging grade 300 steel, slow strain rate tests (SSRT) were performed. A strain rate of 1.0x10-6 s-1 was applied. The tests were carried out in air (middle inert) and the samples immersed in the electrolyte at a simultaneous potential of -1.2 VSEC. The results showed the reduction elongation from 11.06 to 3.89% and from 61,28 to 10% in reduction of area for samples in the solution annealed condition. The greatest reductions were observed in the samples aged at 753 Â10K for 10.8 ks. In this condition the reduction from 1929.26 MPa in air tests to 447.64 MPa in ultimate tensile strength and from 7.30 to 1.62% in elongation under cathodic polarization in the 3,5% NaCl solution was observed. The samples aged at 843 Â10K for 10.8 ks, where about 10% of reverted austenite was identified, showed evidence of hydrogen embrittlement as seen in the samples treated at different conditions. Secondary cracks, perpendicular to the loading direction at the longitudinal surface of the solution annealed fractured samples immersed in 3,5% NaCl solution under cathodic potential were seen. The results evidence that the precipitates and reverted austenite difficult secondary crack propagation in longitudinal section on aged samples. Scanning electron examination showed a change in fractografic features from ductile dimples to quasi-cleavage and microvoid modes when comparing samples without (air tested) and with hydrogen ingress.

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6

Ornek, Cem. "Performance characterisation of duplex stainless steel in nuclear waste storage environment." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/performance-characterisation-of-duplex-stainless-steel-in-nuclear-waste-storage-environment(4db73e9b-c87c-40a6-9778-0b823b1c499f).html.

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The majority of UK’s intermediate level radioactive waste is currently stored in 316L and 304L austenitic stainless steel containers in interim storage facilities for permanent disposal until a geological disposal facility has become available. The structural integrity of stainless steel canisters is required to persevere against environmental degradation for up to 500 years to assure a safe storage and disposal scheme. Hitherto existing severe localised corrosion observances on real waste storage containers after 10 years of exposure to an ambient atmosphere in an in-land warehouse in Culham at Oxfordshire, however, questioned the likelihood occurrence of stress corrosion cracking that may harm the canister’s functionality during long-term storage. The more corrosion resistant duplex stainless steel grade 2205, therefore, has been started to be manufactured as a replacement for the austenitic grades. Over decades, the threshold stress corrosion cracking temperature of austenitic stainless steels has been believed to be 50-60°C, but lab- and field-based research has shown that 304L and 316L may suffer from atmospheric stress corrosion cracking at ambient temperatures. Such an issue has not been reported to occur for the 2205 duplex steel, and its atmospheric stress corrosion cracking behaviour at low temperatures (40-50°C) has been sparsely studied which requires detailed investigations in this respect. Low temperature atmospheric stress corrosion cracking investigations on 2205 duplex stainless steel formed the framework of this PhD thesis with respect to the waste storage context. Long-term surface magnesium chloride deposition exposures at 50°C and 30% relative humidity for up to 15 months exhibited the occurrence of stress corrosion cracks, showing stress corrosion susceptibility of 2205 duplex stainless steel at 50°C.The amount of cold work increased the cracking susceptibility, with bending deformation being the most critical type of deformation mode among tensile and rolling type of cold work. The orientation of the microstructure deformation direction, i.e. whether the deformation occurred in transverse or rolling direction, played vital role in corrosion and cracking behaviour, as such that bending in transverse direction showed almost 3-times larger corrosion and stress corrosion cracking propensity. Welding simulation treatments by ageing processes at 750°C and 475°C exhibited substantial influences on the corrosion properties. It was shown that sensitisation ageing at 750°C can render the material enhanced susceptible to stress corrosion cracking at even low chloride deposition densities of ≤145 µm/cm². However, it could be shown that short-term heat treatments at 475°C can decrease corrosion and stress corrosion cracking susceptibility which may be used to improve the materials performance. Mechanistic understanding of stress corrosion cracking phenomena in light of a comprehensive microstructure characterisation was the main focus of this thesis.

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7

Buckley, J. R. "Hydrogen embrittlement of austenitic stainless steel." Thesis, University of Newcastle Upon Tyne, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315550.

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8

Butler, J. J. F. "Hydrogen embrittlement of austenitic stainless steel." Thesis, University of Newcastle Upon Tyne, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374127.

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9

Hutchings, D. "Hydrogen embrittlement of duplex stainless steel." Thesis, University of Manchester, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.631722.

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Duplex stainless steels (DSS's) are frequently used in oil and gas production and are subsequently subjected to cathodic protection. There is now growing concern about the cathodic evolution of hydrogen produced from this protection system, which may diffuse into the alloy and cause an embrittled condition. DSS's have a microstructure that is a mixture of austenite and ferrite and combines the advantages of these grades, whilst minimising their deficiences. In this research, Zeron 100 DSS was studied in six conditions to investigate the effects of hydrogen embrittlement (HE) on the various strengths and microstructures. The six conditions wer~ as follows: as-received, cold worked, age-hardened (475°C embrittlement), high temperature heat treated, rod and powder. To simulate service environments, 3.5% wt NaCI solution at ambient temperature with an applied potential of -1.1 V (SCE) was used. The effect of pre-charging for up to 550 hours at 80°C was also investigated. Test methods included slow strain rate testing (SSRT), monitoring of transient crack propagation (TCP) using circumferentially notched tensile specimens using a DC potential drop method, acoustic emission CAE) and some conventional bolt loaded fracture mechanics specimens. Test results were correlated with the varying microstructures and environmental conditions and consisted of mechanical properties, threshold crack growth including transient effects and AE data. In this work transgranular cleavage cracks were obtained in the susceptible ferrite phase as a direct result of HE; the depth of these cracks implied a high hydrogen concentration throughout the specimen. The austenite failed by ductile tearing and acted as a physical barrier to the propagation of cleavage cracks. As a result of SSR testing the best material was found to be the powder material; the fine equally dispersed austenite phase caused a lowering of the effective K value. The worst material was the high temperature heat treated type because it contained more ferrite (11:1 72%). The age-hardened material was also susceptible because of the hard and brittle ex' phase. However, regardless of the environment the UTS remained virtua]]y unchanged for each individual material, indicating that most cracking occurred in the post-UTS stage of the test. With the TCP test a lowering of the fracture load was found when an HE environment was used; daldt vs Kq curves were produced, however the DC potential drop equipment could not accurately measure crack growth because of the bridging effect of the austenite phase. The most susceptible microstructures were again the age-hardened and heat treated types. The hydrogen evolution reaction (HER) was also investigated by creating a fresh surface on the as-received DSS and studying the changes in the HER. This work showed that the effect of scratching is irreversible. Also the oxide film can not be totaHy reduced electrochemica]]y and only mechanical methods can remove the oxide films entirely. Fina]]y a means of detecting "475°C embrittlement" of DSS's was investigated using an electrochemical technique in 5M HCI. i-E curves were produced which showed the reactivation of the ferrite and austenite phases in the as-received material. By age-hardening at 475°C the two reactivation peaks merged.

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10

Hsieh, Jang-Hsing. "Hydrogen embrittlement of cold worked plain carbon steel." Thesis, Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/12016.

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11

El-Yazgi, Abdullatif Abdallah. "The effect of hydrogen on the mechanical behaviour of duplex stainless steel." Thesis, University of Newcastle Upon Tyne, 1995. http://hdl.handle.net/10443/719.

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Duplex stainless steels are commonly used in environments that are expected to produce hydrogen i. e. in sour environments and sea water applications, often under cathodic protection. Under these conditions there is a concern about their susceptibility to hydrogen embrittlement. The effect of hydrogen, both external and internal, on the mechanical properties and the fracture characteristics of duplex stainless steels Type 2205 and 2507 have been studied by slow strain rate techniques using smooth tensile specimens. Specimens were strained to failure in air after high pressure hydrogen thermal charging, in a hydrogen atmosphere, in a hydrogen sulphide environment under open circuit potential condition, and whilst cathodically polarized at different potentials in distilled water with 100 wppm potassium sulphate added, in 3.5% aqueous sodium chloride, or in NACE solution. All the environments produced a major reduction in ductility that increases linearly with decrease in strain rate. The severity of the embrittlement depended upon whether the supply of hydrogen was external or internal. Internal hydrogen, as in thermally charged specimens, produced a more profound loss in ductility than straining in a hydrogen atmosphere and prolonged room temperature aging of these specimens, for up to 3 years, resulted in insignificant recovery of ductility, emphasizing the role of the austenite as a hydrogen reservoir. Provision of hydrogen at very high fugacities (cathodic polarization) during straining indicated that the potential at which loss in ductility is first noted corresponds to the hydrogen evolution potential for the particular solution involved. The presence of chloride ion seems to have no significant effect on the loss in ductility- The presence of hydrogen sulphide in the environment, however, introduced the complication of extensive chemical attack during and after crack propagation. The loss in ductility increased as the pH of the solution decreased and, irrespective of pH, maximum embrittlement occurred at some particular temperature between 20 and 90'C. The latter is attributed to the two competing processes of hydrogen ABSTRACT embrittlement and corrosion. A minimum chloride ion concentration of 300 wppm seems necessary to maintain the maximum embrittlement. The ultimate tensile strength of the steel is not affected by hydrogen since cracking only occurs after it is exceeded. Cracks initiate and grow preferentially through the ferrite phase, with fracture surfaces exhibiting quasi-cleavage features; the austenite often failed in a ductile mode. The proportion and distribution of the two phases has a significant effect on the degree of embrittlement. The presence of greater amounts of austenite seems to inhibit crack propagation, but may act as a hydrogen source or reservoir for the embrittlement of the ferrite phase. Straining of the as received weldments, which had been annealed after welding, showed no evidence of hydrogen embrittlement, but an attempt was made to simulate via heattreatment the structures that could occur in the heat affected zone of the weld and these structures had inferior mechanical properties in the presence of hydrogen.

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Stroe, MIOARA ELVIRA. "Hydrogen embrittlement of ferrous materials." Doctoral thesis, Universite Libre de Bruxelles, 2006. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210889.

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This work deals with the damage due to the simultaneous presence of hydrogen in atomic form and stress – straining.

The aim of this work is twofold: to better understand the hydrogen embrittlement mechanisms and to translate the acquired knowledge into a more appropriate qualification test.

The phenomena of hydrogen entry and transport inside the metals, together with the different types of damages due to the presence of hydrogen, are presented.

The analysis of the most important models proposed up to now for hydrogen embrittlement (HE) indicated that the slow dynamic plastic straining is a key factor for the embritteling process. There is a synergistic effect of hydrogen – dislocations interactions: on one hand hydrogen facilitates the dislocations movement (according to the HELP mechanism) and on the other hand dislocations transport hydrogen during their movement when their velocity is lower than a critical value.

This work is focused on supermartensitic stainless steels, base and welded materials. The interest on these materials is due to their broad use in offshore oil production.

First, the material’s characterisation with regards to hydrogen content and localisation was performed. This was conducted in charging conditions that are representative of industrial applications.

Because of previous industrial experience it was necessary to find a more appropriate qualification test method to asses the risk of HE.

In this work we proposed the stepwise repeated slow strain rate test (SW R – SSRT) as a qualification test method for supermartensitic stainless steels.

This test method combines hydrogen charging, test duration, plastic, dynamic and slow strains. Thus, this test method is coherent with both the model HELP proposed for hydrogen embrittlement and the observations of industrial failures.

The stepwise repeated slow strain rate test (SW RSSRT) is interesting not only as a qualification test of martensitic stainless steels, but also as a qualification test of conditions for using these materials (type of straining, range of strain and stress, strain rate, hydrogen charging conditions, etc.).

Ce travail se rapporte à l’endommagement provoqué par la présence simultanée de l’hydrogène sous forme atomique et une contrainte (appliquée où résiduelle).

Ce travail a comme but une meilleure compréhension du mécanisme de la fragilisation par l’hydrogène (FPH) et la recherche d’un essai de qualification qui soit cohérent avec ce mécanisme.

Les phénomènes liés à l’entrée et au transport de l’hydrogène au sein des métaux, ensemble avec les différents types d’endommagements dus à la présence de l’hydrogène, sont présentés.

L’analyse des modèles proposés jusqu’au présent pour la fragilisation par l’hydrogène (FPH) suggère que la déformation lente plastique dynamique est le facteur clé pour le processus de la fragilisation. Il y a un effet synergétique des interactions entre l’hydrogène et les dislocations: d’un coté l’hydrogène facilite le mouvement des dislocations (d’après le modèle HELP) et d’un autre coté les dislocations transportent l’hydrogène pendant leur mouvement, pourvu que leur vitesse soit en dessous d’une valeur critique.

Le travail a été conduit sur des aciers supermartensitiques, matériau de base et soudé. L’intérêt pour ces matériaux réside de leur large utilisation dans la production du pétrole en offshore.

D’abord, le matériau a été caractérisé du point de vu de la teneur et de la localisation de l’hydrogène. Les essais ont été conduits dans des conditions représentatives pour les cas industriels.

L’expérience industrielle d’auparavant indique qu’il est nécessaire de trouver un test de qualification plus approprié pour estimer la susceptibilité à la fragilisation par l’hydrogène.

Dans ce travail on propose un essai de traction lente incrémentée (SW R – SSRT) comme méthode de qualification pour les aciers supermartensitiques.

L’essai combine le chargement en hydrogène, la durée d’essai, la déformation lente, plastique et dynamique. Donc, cette méthode d’essai est cohérente avec le modèle HELP proposé pour FPH et les observations des accidents industriels.

Cet essai est intéressant pas seulement comme essai de qualification pour les aciers supermartensitiques, mais aussi comme essai de qualification pour les conditions d’utilisation des ces matériaux (type de déformation, niveau de déformation et contrainte, vitesse de déformation, conditions de chargement en hydrogène, etc.).

Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished

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13

Barritt, Andrew Stephen. "Detection of hydrogen embrittlement in steel and steel alloys using methods of neutron radiography." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/32597.

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14

Dias, Joachim Octave Valentin. "The first high-strength bainitic steel designed for hydrogen embrittlement resistance." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/273831.

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The phenomenon of hydrogen embrittlement in steel has been known for over 150 years. Hydrogen-resistant alloys have been developed to mitigate this effect and three types of alloys with optimised structures have been enhanced over the years: nickel alloys, stainless steels, and quenched and tempered martensitic low alloy steels. Nevertheless, those alloys are limited in terms of strength and ductility. The aim of the work presented in this thesis was to design bainitic alloys with hydrogen embrittlement resistance, and with a better combination of strength and ductility than conventional alloys. In the novel alloys, two microstructural features were produced to mitigate the damaging effects of hydrogen: 1. A percolating austenite structure, in which hydrogen diffusion is orders of magnitude lower than in bainitic ferrite. This feature was introduced to impede the ingress of hydrogen through the structure. 2. Iron carbide traps, which can form at the bainite transformation temperature. This feature was introduced to trap diffusible hydrogen and prevent it from causing damage. The alloys, designed with the aid of computer models and phase transformation theory, contained a volume fraction of retained austenite above its percolation threshold, theorised as 0.1, which was proven to form an effcient barrier to hydrogen ingress. The effective diffusivity of hydrogen, measured using an electrochemical permeation technique, was shown to decrease with increasing austenite fraction up to the percolation threshold. It was seen to plateau for austenite fractions comprised between 0.1 and 0.18, and to decrease further for fractions above 0.18. The compositions of the alloys were precisely selected to allow for iron carbides to precipitate during the bainitic transformation reaction. Until the present work, only alloy carbides V4C3, TiC and NbC had been reported to strongly trap hydrogen. The literature was very inconsistent regarding the trapping ability of cementite, with reported trap binding energies ranging from 11 to 66 kJ mol−1. The carbides produced in the alloys were identified as cementite. The cementite fraction was measured to be 0.001 ± 0.0001 for one of the designed alloys, which is the lowest ever reported carbide fraction in steel measured using a simple X-ray diffraction technique. Experimental thermal desorption spectroscopy data were used to determine the binding energy of hydrogen to cementite to be 37.5 kJ mol−1, suggesting that cementite is not a strong hydrogen trap. Further tests performed after room temperature hydrogen degassing displayed insignifcant amount of trapped hydrogen, thus confrming the reversible nature of cementite traps. The comparison of two successive transients using the electrochemical permeation technique confirmed that result. The influence of the heat treatments on the microstructures and on the mechanical properties of the designed alloys was extensively studied. The novel alloys met all the set requirements, and successfully outperformed conventional alloys in terms of strength and ductility. They did not meet the NACE TM0316-2016 standard requirement for operation in hydrogen-rich environments, likely owing to the inadequate trapping ability of cementite. Future work should focus on exploring the possible use of alternative carbides for hydrogen trapping in bainitic structures.

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15

Alexander, Matthew S. "The influence of aggressive marine environments on the hydrogen embrittlement and hydrogen uptake of steel." Thesis, University of Manchester, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488077.

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16

Alsarraf, Jalal. "Hydrogen embrittlement susceptibility of super duplex stainless steels." Thesis, Cranfield University, 2010. http://dspace.lib.cranfield.ac.uk/handle/1826/4562.

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This thesis describes the metallurgical and environmental factors that influence hydrogen embrittlement of super duplex stainless steels and presents a model to predict the rate at which embrittlement occurs. Super duplex stainless steel has an austenite and ferrite microstructure with an average fraction of each phase of approximately 50%. An investigation was carried out on the metallurgical and environmental factors that influence hydrogen embrittlement of super duplex stainless steels. Tensile specimens of super duplex stainless steel were pre-charged with hydrogen for two weeks in 3.5% NaCl solution at 50º C at a range of applied potentials to simulate the conditions that exist when subsea oilfield components are cathodically protected in seawater. The pre-charged specimens were then tested in a slow strain rate tensile test and their susceptibility to hydrogen embrittlement was assessed by the failure time, reduction in cross-sectional area and examination of the fracture surface. The ferrite and austenite in the duplex microstructures were identified by analysing their Cr, Ni, Mo and N contents in an electron microscope, as these elements partition in different concentrations in the two phases. It was shown that hydrogen embrittlement occurred in the ferrite phase, whereas the austenite failed in a ductile manner. An embrittled region existed around the circumference of each fracture surface and the depth of this embrittlement depended on the hydrogen charging time and the potential at which the charging had been carried out. The depth of embrittlement was shown to correlate with the rate of hydrogen diffusion in the alloy, which was measured electrochemically using hydrogen permeation and galvanostatic methods. A two-dimensional diffusion model was used to calculate the hydrogen distribution profiles for each experimental condition and the model could be employed to provide predictions of expected failure times in stressed engineering components.

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17

Kilgallon, P. J. "The effect of sulphate reducing bacteria on the hydrogen absorption of cathodically protected high strength low alloy steel." Thesis, Cranfield University, 1994. http://dspace.lib.cranfield.ac.uk/handle/1826/7253.

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The hydrogen embrittlement of two HSLA steels was studied in conditions typical of the marine environment. Double cantilever beam specimens, heat treated to produce the microstructure in the heat affected zone of a weld, were tested in seawater containing sulphate reducing bacteria (SRB) over a range of cathodic protection (CP) potentials and the threshold stress intensities ([Threshold Stress Intensity]) were recorded. The hydrogen concentration absorbed by the steel ([Surface Hydrogen Concentration]) was measured and shown to be higher at more negative CP potentials and significantly increased when SRB were present. An inverse relationship was established between log [Threshold Stress Intensity] and [Surface Hydrogen Concentration]. It was concluded that crack propagation occurs by a single mechanism whether or not SRB are present. Three point bend specimens of both steels were machined from welded plate. Corrosion fatigue tests were carried out in seawater with and without SRB. The presence of active SRB caused increased crack growth rates. Sediment samples were collected from the River Mersey and the base of a North Sea platform. In addition, SRB were added as an inoculum to artificial seawater. SRB numbers were enumerated and their activities assessed by measuring the concentrations of sulphide generated. Hydrogen permeation tests were performed on steel held at a range of CP potentials and exposed to each environment. Measurements were also carried out in seawater containing chemically prepared sulphides. Hydrogen absorption was shown to be enhanced when SRB were present and to be related to the total sulphide (TS) concentration in the environment. High hydrogen concentrations were produced by chemically prepared sulphides and the nature and thickness of the sulphide film appeared to be important in determining the extent of hydrogen absorption. Chemically produced sulphide gave sustained levels of absorbed hydrogen, but those generated biogenically decayed rapidly unless the TS concentration was maintained in the solution.

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18

Evans, Juliet M. "The effect of nickel plating on hydrogen embrittlement of high strength steel." Thesis, Cranfield University, 1992. http://dspace.lib.cranfield.ac.uk/handle/1826/3238.

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The microstructure of high strength steel is susceptible to delayed failure caused by the absorption of hydrogen produced either during cathodic charging or electroplating. When 0.8%C and AISI 4340 steel are subjected to constant load testing, a wide range of failure times is observed. By applying Weibull statistics small changes in experimental parameters such as heat-treatment are detected readily and are explained in the terms of hydrogen trapping at microstructural defects. During the electroplating of steel in a double-cell, quantitative measurements are made of the amount of hydrogen permeated. Current densities are measured in the range 2- 40 mAcm2 and it is shown that, although the lowest current density produces the most mechanically sound plate, it also causes the largest amount of hydrogen absorption. The nickel deposit is found to act as a reservoir for reversibly trapped hydrogen allowing diffusion to continue into the steel after the cessation of plating. Permeation measurements were taken on AISI 4340 steel using an electrochemical probe developed from the Barnacle Electrode. The effects of cathodically charging and electroplating with nickel are compared. Exposure of the steel to the atmosphere is shown to have an important influence on the hydrogen content after a period of time due to a limited occurrence of corrosion. Various post- plating treatments are commonly used to remove a damaging concentration of hydrogen and the quantitative effects of such treatments are described. Finally, a mathematical model is proposed which explains the reason for the wide spread of delayed failure times. It is found that if the stress intensity necessary to initiate a crack is known and, provided either the nominal stress or the crack size is known, it is possible to calculate either the allowable defect size or the allowable stress below which cracking is not expected to occur.

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19

Sobeih, Mahmoud Omar R. J., and Moazzam Maqsood. "Influence of Hydrogen Charging on Mechanical Properties and Microstructure of Structural Steel S235 & Stainless Steel 316L." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-18792.

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The present paper studied the influence of hydrogen on the mechanical properties and microstructure of the materials. This study is done by doing hydrogen charging of steel bar specimens. The two types of steel are used for study, structural steel S235 and stainless steel 316L. The tensile test has been performed to get the data of the charged and uncharged specimens. Different strain rates were used to study the effect of the material after charging. The charging time ranged from 24 hours to 144 hours. The specimens are cylindrical shape. Digital image analysis is performed for the uncharged specimens to correctly analyse the strain field and compare it with the results from tensile test. For DIC analysis a GOM correlate software was used to study the 2D strain analysis of the specimen. The results show that hydrogen influences the mechanical properties of the material and microstructure.

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20

Chen, Yi-Sheng. "Characterisation of hydrogen trapping in steel by atom probe tomography." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:9d8ee66f-176d-4ac1-aad6-ccb33efc924d.

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Hydrogen embrittlement (HE), which results in an unpredictable failure of metals, has been a major limitation in the design of critical components for a wide range of engineering applications, given the near-ubiquitous presence of hydrogen in their service environments. However, the exact mechanisms that underpin HE failure remain poorly understood. It is known that hydrogen, when free to diffuse in these materials, can tend to concentrate at a crack tip front. In turn, this facilitates crack propagation. Hence one of the proposed strategies for mitigating HE is to limit the content of freely diffusing hydrogen within the metal atomic lattice via the introduction of microstructural hydrogen traps. Further, it is empirically known that the introduction of finely-dispersed distribution of nano-sized carbide hydrogen traps in ferritic steel matrix can improve resilience to HE. This resilience has been attributed to the effective hydrogen trapping of the carbides. However, conclusive atomic-scale experimental evidence is still lacking as to the manner by which these features can impede the movement of the hydrogen. This lack of insight limits the further progress for the optimisation of the microstructural design of this type of HE-resistant steel. In order to further understand the hydrogen trapping phenomenon of the nano-sized carbide in steel, an appropriate characterisation method is required. Atom probe tomography (APT) has been known for its powerful combination of high 3D spatial and chemical resolution for the analysis of very fine precipitates. Furthermore, previous studies have shown that the application of isotopic hydrogen (²H) loading techniques, combined with APT, facilitates the hydrogen signal associated to fine carbides to be unambiguously identified. However, the considerable experimental requirements as utilised by these previous studies, particularly the instrumental capability necessary for retention of the trapped hydrogen in the needle-shaped APT specimen, limits the study being reproduced or extended. In this APT study, a model ferritic steel with finely dispersed V-Mo-Nb carbides of 10-20 nm is investigated. Initially, existing specialised instrumentation formed the basis of a cryogenic specimen chain under vacuum, so as to retain loaded hydrogen after an electrolytic charging treatment for APT analysis. This work confirms the importance of cryogenic treatment for the retention of trapped hydrogen in APT specimen. The quality of the obtained experimental data allows a quantitative analysis on the hydrogen trapping mechanism. Thus, it is conclusively determined that interior of the carbides studied in this steel acts as the hydrogen trapping site as opposed to the carbide/matrix interface as commonly expected. This result supports the theoretical investigations proposing that the hydrogen trapping within the carbide interior is enabled by a network of carbon vacancies. Based on the established importance of the specimen cold chain in these APT experiments, this work then successfully develops a simplified approach to cryo-transfer which requires no instrumental modification. In this approach there is no requirement for the charged specimen to be transferred under vacuum conditions. The issue of environmental-induced ice contamination on the cryogenic sample surface in air transfer is resolved by its sublimation in APT vacuum chamber. Furthermore, the temperature of the transferred sample is able to be determined independently by both monitoring changes to vacuum pressure in the buffer chamber and also the thermal response of the APT sample stage in the analysis chamber. This simplified approach has the potential to open up a range of hydrogen trapping studies to any commercial atom probe instrument. Finally, as an example of the use of this simplified cryo-transfer technique, targeted studies for determining the source of hydrogen adsorption during electropolishing and electrolytic loading process are demonstrated. This research provides a critical verification of hydrogen trapping mechanism of fine carbides as well as an achievable experimental protocol for the observation of the trapping of individual hydrogen atoms in alloy microstructures. The methods developed here have the potential to underpin a wide range of possible experiments which address the HE problem, particularly for the design of new mitigation strategies to prevent this critical issue.

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21

Allen, Quentin Scott. "Microstructural Evaluation of Hydrogen Embrittlement and Successive Recovery in Advanced High Strength Steel." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6617.

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Advanced high strength steels (AHSS) have high susceptibility to hydrogen embrittlement, and are often exposed to hydrogen environments in processing. In order to study the embrittlement and recovery of steel, tensile tests were conducted on two different types of AHSS over time after hydrogen charging. Concentration measurements and hydrogen microprinting were carried out at the same time steps to visualize the hydrogen behavior during recovery. The diffusible hydrogen concentration was found to decay exponentially, and equations were found for the two types of steel. Hydrogen concentration decay rates were calculated to be -0.355 /hr in TBF steel, and -0.225 /hr in DP. Hydrogen concentration thresholds for embrittlement were found to be 1.04 mL/100 g for TBF steel, and 0.87 mL/100g for DP steel. TBF steel is predicted to recover from embrittlement within 4.1 hours, compared to 7.2 hours in DP steel. A two-factor method of evaluating recovery from embrittlement, requiring hydrogen concentration threshold and decay rate, is explained for use in predicting recovery after exposure to hydrogen. Anisotropic hydrogen diffusion rates were also observed on the surface of both steels for a short time after charging, as hydrogen left the surface through <001> and <101> grains faster than grains with <111> orientations. This could be explained by differences in surface energies between the different orientations.

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22

Chou, Kuo-chin. "Hydrogen diffusion, trapping and crack growth in two low carbon steels with different contents of sulfur /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu148758461216328.

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23

Hillier, Elizabeth M. K. "The effect of zinc-cobalt electroplating on the hydrogen embrittlement of high strength steel." Thesis, Cranfield University, 2001. http://dspace.lib.cranfield.ac.uk/handle/1826/3244.

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Electroplated cadmium coatings are widely used in the aerospace industry to provide corrosion protection for components such as fasteners, which are manufactured from high strength steels. Due to environmental and safety concerns with regard to the use of cadmium, there is a requirement to investigate suitable replacements. Any alternate coating, in addition to effective corrosion protection, must not have deleterious effects on the steel substrate. Hydrogen is known to be absorbed during electroplating and there are concerns that this could cause hydrogen embrittlement of high strength steel fasteners. This study has investigated the effect of zinc-cobalt electroplating on the embrittlement of high strength steels used for aerospace applications, due to promising corrosion properties. i Permeation measurements have been used to measure the hydrogen uptake during electroplating, and slow strain rate testing performed to establish the effect of hydrogen on the embrittlement of the steel substrate. The influences of bath composition, temperature and pH have been studied, plus the addition of other iron group elements to the plating bath to minimise the risk of embrittlement. Hydrogen that has passed into the metal substrate has been located by a decorative mapping technique that also showed the high concentration present in the electroplated coatings. Corrosion tests have been executed to assess the performance of the electroplated coatings that have been tested. The factors that affect the ernbrittlement of zinc-cobalt electroplated high strength steels and the methods, including modulated multi-layer coatings and baking, that could be used for its control are described. 10

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24

Needham, William Donald. "Stress corrosion cracking and hydrogen embrittlement of thick section high strength low alloy steel." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/10945/22123.

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An experimental study was conducted to evaluate the corrosion performance of weldments of a high strength low alloy(HSLA) steel in a simulated seawater environment. This steel, designated HSLA80, was developed by the United States Navy for use in ship structural applications. Stress corrosion CRACKING(SCC) and hydrogen embrittlement(HEM) were investigated by conducting 42 Wedge-Opening load(WOL) tests as a function of stress intensity and corrosion potential and 33 Slow Strain Rate(SSR) tests as a function of strain rate and corrosion potential. The corrosion potentials were chosen to simulate the environmental conditions of free corrosion, cathodic protection and hydrogen generation. The results from this investigation indicated that HSLA 80 base metal and weldments were susceptible to hydrogen assisted cracking(HAC) in a seawater environment under conditions of continuous plastic deformation and triaxial stress in the presence of hydrogen. The heat-affected zone of the weldment was found to be the most susceptible portion of the weld joint. A lower bound was established for the critical stress intensity for stress corrosion cracking for HSLA 80 base metal and weldments.(Theses)

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25

Haglund, Adam. "Reduction of hydrogen embrittlement on Electrogalvanized Ultra High Strength Steels." Thesis, Uppsala universitet, Institutionen för kemi - Ångström, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-236603.

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Ultra-high strength steels is known to be susceptible for hydrogen embrittlement at very low concentrations of hydrogen. In this thesis three methods to prevent or reduce the hydrogen embrittlement in martensitic steel, with tensile strength of 1500 MPa, were studied. First, a barrier layer of aluminium designed to prevent hydrogen to enter the steel, which were deposited by vacuum evaporation. Second, a decarburization process of the steels surface designed to mitigate the induced stresses from cutting. Last, a hydrogen relief treatment at 150°C for 11 days and 200°C for 4 days, to reduce the hydrogen concentration in the steel. The effect of the hydrogen embrittlement was analyzed by manual measurements of the elongations after a slow strain rate testing at 5*10-6 mm/s, and the time to fracture in an in-situ constant load test with a current density of 1.92 mA/cm2 in a 0.5 M Na2SO4 solution. The barrier layer showed an increase in time to fracture, but also a decrease in elongations. The decarburized steel had a small increase in the time to fracture, but not enough to make it a feasible process. The hydrogen relief treatment showed a general decrease in hydrogen concentrations, but the elongation measurements was irregular although with a tendency for improvement. The simplicity of the hydrogen relief treatment makes it an interesting process to reduce the influence of hydrogen embrittlement. However, more investigations are necessary.

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26

Ghasemi, Rohollah. "Hydrogen-assisted stress corrosion cracking of high strength steel." Thesis, KTH, Skolan för kemivetenskap (CHE), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-50416.

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In this work, Slow Strain Rate Test (SSRT) testing, Light Optical Microscopy (LOM) and Scanning Electron Microscopy (SEM) were used to study the effect of micro-structure, corrosive environments and cathodic polarisation on stress corrosion cracking (SCC) of two grades of high strength steels, Type A and Type B. Type A is manufactured by quench and tempered (Q&T) method. Type B, a normalize steel was used as reference. This study also supports electrochemical polarisation resistance method as an effective testing technique for measuring the uniform corrosion rate. SSRT samples were chosen from base metal, weld metal and Heat Affected Zone (HAZ). SSRT tests were performed at room temperature under free corrosion potential and cathodic polarisation using 4 mA/cm2 in 1 wt% and 3.5 wt% NaCl solutions. From the obtained corrosion rate measurements performed in 1 wt% and 3.5 wt% NaCl solutions it was observed that increased chloride concentration and dissolved oxygen content enhanced the uniform corrosion for all tested materials. Moreover, the obtained results from SSRT tests demonstrate that both Q&T and normalized steels were not susceptible to SCC in certain strain rate(1×10-6s-1) in 1 wt% and 3.5 wt% NaCl solutions under free corrosion potential. It was con-firmed by a ductile fracture mode and high reduction in area. The weld metal of Type A with acicular ferrite (AF), pro-eutectoid (PF) and bainite microstructure showed higher susceptibility to hydrogen assisted stress corrosion cracking compared to base metal and HAZ. In addition, typical brittle intergranular cracking with small reduction in area was observed on the fracture surface of the Type A due to hydrogen charging.

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27

Hays, Richard A. "Surface residual stress effects on stress corrosion cracking/hydrogen embrittlement behavior of AISI 4340 steel." Thesis, Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/80148.

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A series of experiments was performed in an attempt to measure the effects of surface residual stresses on the stress corrosion cracking/hydrogen embrittlement (SCC/HE) behavior of AISI 4340 steel. Stress corrosion tests were performed under load control on cylindrical and notched tensile specimens in acidified 3.5% NaCl solution. The electrochemical potential of the specimens was maintained at -0.7 V versus a saturated calomel reference electrode. Time to failure for specimens tested at various applied and residual stress levels was measured. Stress relieved specimens as well as specimens containing mechanically induced residual stresses were tested. Residual stresses were estimated using Neuber's rule and were measured using an x-ray diffraction technique. In all cases, the sum of the applied and residual stresses was greater than zero. Test results showed the initiation of SCC/HE cracks to be insensitive to the effects of surface residual stresses under the conditions evaluated. This is probably a result of the total time to failure criterion used to evaluate the SCC/HE tests. The extremely aggressive environment used in these experiments apparently led to rapid crack initiation, even in specimens containing compressive residual stresses. Another possible explanation of the insensitivity of this series of tests is crack initiation in the interior of the specimens below the depth of the mechanically induced residual stresses.
Master of Science

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28

Carr, Martin J. "An investigation of hydrogen embrittlement of high strength steel due to zinc/nickel alloy electroplating." Thesis, Cranfield University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283258.

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29

Bai, Yu. "Effect of Grain Size on the Hydrogen Embrittlement Behaviors in High-manganese Austenitic Steels." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/202713.

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30

Stopher, Miles Alexander. "Hydrogen embrittlement in nuclear and bearing applications : from quantum mechanics to thermokinetics and alloy design." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/282992.

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Hydrogen embrittlement in ferrous and non-ferrous alloys is, and has been for over a century, a prominent issue within many sectors of industry. Despite this, the mechanisms by which hydrogen embrittlement occurs and the suitable means for its prevention are yet to be fully established. As hydrogen fuel becomes a prominent feature in modern concepts of a sustainable global energy infrastructure and nuclear power enters its renaissance, with commercially viable fusion plants on the horizon, hydrogen embrittlement is becoming an ever more pertinent issue. This has led to a considerable demand for novel alloys resistant to hydrogen embrittlement, notably within the bearings industry, where the commonly conflicting properties of high strength and hydrogen embrittlement resistance are required. This work investigates the mechanisms through which hydrogen embrittlement and irradiation damage occur in steels and nickel-based alloys respectively, with novel alloys designed for improved resistance. Through the engineering of secondary phases, optimised for helium and/or hydrogen trapping capacity, the novel alloys present the benefits of such trapping species with respect to embrittlement resistance. Such species have been studied in depth with respect to their interactions with hydrogen, establishing a novel mechanism of hydrogen embrittlement - the hydrogen enhanced dissolution and shearability of precipitates, leading to enhanced localised plasticity.

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31

Buntain, Ryan John. "Effect of Microstructure on Hydrogen Assisted Cracking in Dissimilar Welds of Low Alloy Steel Pipes Joined with Nickel Based Filler Metals." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1577785066479763.

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32

Doyle, Richard John-Paul. "An investigation into the hydrogen embrittlement susceptibility of experimental 304 stainless steel alloys modified with ruthenium and palladium additions." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6763/.

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The motivation for this work was provided by the results of an interdisciplinary, multi-university research programme funded by the Ministry of Defence. The significant finding in question was that the stress corrosion cracking (SCC) resistance of AISI type 304 stainless steel (SS) alloys can be significantly improved by the addition of the platinum group metals (PGM), ruthenium and palladium. The increased SCC resistance could be attributed to the enhancement of the cathodic hydrogen reduction reaction. Thus, the primary objective of this work was to confirm that the increase in hydrogen production at the surface would not counteract the improvement in SCC resistance by increasing the susceptibility to hydrogen embrittlement (HE). Electrochemical hydrogen charging was employed and melt extraction was used to measure the bulk concentration of absorbed hydrogen as a function of alloy chemistry. Both Ru and Pd doped experimental 304 SSs showed a decrease in the concentration of absorbed hydrogen compared to an experimental standard 304 SS (i.e., a controlled, non PGM-doped reference 304). This result is thought to be due to the PGMs enhancing the recombination kinetics of adsorbed hydrogen. Ru proved more effective than Pd at hindering absorption and this is likely associated to the more homogenous distribution of Ru in solid solution. Slow strain rate tensile (SSRT) testing was performed in air at sub-ambient temperatures on pre-hydrogen charged specimens. PGM addition was found not to increase the susceptibility of 304 to HE. Conversely, an approximately equal enhancement of the HE resistance was observed for the addition of both Ru and Pd. The modest improvements are attributed to the reduced concentration of absorbed hydrogen, with a further possible beneficial trapping effect of Pd concentrated bands, contributing to the HE resistance of Pd doped 304.

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33

Kivisäkk, Ulf. "Influence of hydrogen on corrosion and stress induced cracking of stainless steel." Doctoral thesis, KTH, Korrosionslära, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12436.

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Hydrogen is the smallest element in the periodical table. It has been shown in several studies that hydrogen has a large influence on the corrosion and cracking behaviour of stainless steels. Hydrogen is involved in several of the most common cathode reactions during corrosion and can also cause embrittlement in many stainless steels. Some aspects of the effect of hydrogen on corrosion and hydrogen-induced stress cracking, HISC, of stainless steels were studied in this work. These aspects relate to activation of test specimens for uniform corrosion testing, modification of a test cell for dewpoint corrosion testing and the mechanism of hydrogen-induced stress cracking. The results from uniform corrosion testing of superduplex stainless steels indicated that there is a large difference between passive and activated surfaces in hydrochloric acid and in lower concentrations of sulphuric acid. Hence, initial activation of the test specimen until hydrogen evolution can have a large influence on the results. This may provide another explanation for the differences in iso-corrosion curves for superduplex stainless steels that have previously been attributed to alloying with copper and/or tungsten. In concentrated sulphuric acid, potential oscillations were observed; these oscillations activated the specimen spontaneously. Due to these potential oscillations the influence of activation was negligible in this acid. An experimental set-up was developed for testing dewpoint corrosion of stainless steels in a condensate containing 1 % hydrochloric acid. There was an existing experimental set-up that had to be modified in order to avoid azeotroping of the water and hydrogen chloride system. A separate flask with hydro chloric acid was included in the experimental set-up. The final set-up provided reasonably good agreement with field exposures in contrary to much higher corrosion rates in the original set-up. Relaxation and low temperature creep experiments have been performed with several stainless steels in this work. The aim was to understand how creep and relaxation relates to material properties and the relative ranking between the tested materials. For low temperature creep with a load generating stresses below the yield strength, as well relaxation at stress levels above and below the yield strength, the same ranking with respect to changes in mechanical properties of the steel grades was found. For low temperature creep with a load level above the yield strength, the same ranking was not obtained. This effect can most probably be explained by annihilation and generation of dislocations. During low temperature creep above the yield strength, dislocations were generated. In addition, low temperature creep experiments were performed forone superduplex stainless steel in two different product forms with differentaustenite spacing in the microstructure. The superduplex material experienced low temperature creep at a lower load level for the material with large austenite spacing compared to the one with smaller austenite spacing. Also this differenceis influenced by dislocations. In a material with small austenite spacing the dislocations have more obstacles that they can be locked up against. Studies of the fracture surfaces of hydrogen induced stress cracking, HISC, tested duplex stainless steels showed that HISC is a hydrogen-enhanced localised plasticity, HELP, mechanism. Here a mechanism that takes into account the inhomogeneous deformation of duplex stainless steels was proposed. This mechanism involves an interaction between hydrogen diffusion and plastic straining. Due to the different mechanical properties of the phases in a superduplex stainless steel, plastic straining due to low temperature creep can occur in the softer ferrite phase. A comparison between low temperature creep data showed that for the coarser grained material, HISC occurs at the load levelwhen creep starts. However, in the sample with small austenite spacing, HISC did not occur at this load level. Microhardness measurements indicated that the hydrogen level in the ferrite was not high enough to initiate cracking in the coarser material. The proposed mechanism shows that occurrence of HISC is an interaction between local plasticity and hydrogen diffusion.
QC20100618

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34

Bergmann, Clemens [Verfasser], Michael [Gutachter] Pohl, and Werner [Gutachter] Theisen. "Hydrogen embrittlement resistance evaluation of advanced high strength steel grades in automotive applications / Clemens Bergmann ; Gutachter: Michael Pohl, Werner Theisen ; Fakultät für Maschinenbau." Bochum : Ruhr-Universität Bochum, 2020. http://d-nb.info/1219736635/34.

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35

Iacoviello, Francesco. "Fragilisation par l'hydrogène de l'acier inoxydable austéno-ferritique Z2CND22 05 : rôle de la microstructure." Châtenay-Malabry, Ecole centrale de Paris, 1997. http://www.theses.fr/1997ECAP0536.

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Les aciers inoxydables austéno-ferritiques sont caractérisés par des propriétés mécaniques élevées et par une bonne résistance à la corrosion, notamment à la corrosion sous contrainte et par piquration. En revanche, leur structure duplex montre une sensibilité à la fragilisation par l'hydrogène. Parmi les aciers inoxydables austéno-ferritiques, la nuance z2cnd22 05 s'est progressivement imposée comme nuance de base et elle est la plus répandue des nuances austéno-ferritiques actuellement utilisées. Dans cette étude, nous avons analysé le comportement mécanique en traction et la cinétique de fissuration par fatigue de l'acier inoxydable austéno-ferritique z2cnd22 05, chargé ou non en hydrogène après différents traitements thermiques de revenu. Les températures et les durées des traitements thermiques de revenu ont été choisies avec la double finalité de fournir une caractérisation la plus complète possible de l'influence de toutes les phases secondaires, carbures et nitrures et, en plus, d'analyser d'une façon plus approfondie les températures critiques connues par la bibliographie et les résultats des essais de traction. De plus, nous avons perfectionné une technique d'évaluation du coefficient de diffusion, solution alternative à la mesure par perméation. Par ailleurs, nous avons utilisé la technique de l'analyse thermique pour mesurer l'énergie d'activation des pièges présents dans l'acier à l'état de livraison. Les résultats obtenus permettent d'établir les conclusions suivantes : - les joints de grains et les dislocations ont une influence négligeable sur le processus de diffusion de l'hydrogène - la quantité d'hydrogène absorbé dépend de la microstructure : la présence d'autres phases secondaires, carbures et nitrures dans la ferrite diminue fortement cette quantité. Cette diminution est probablement due a une variation de la solubilité et de la diffusivité de l'hydrogène - le chargement en hydrogène de l'acier duplex implique une forte diminution de #m% pour toutes les températures de revenu, sauf a 1050c ou la densité des dislocations est très basse et toutes les phases secondaires, carbures et nitrures, sont dissoutes. - le chargement en hydrogène de l'acier duplex n'induit pas de variation de r#e, tandis que la diminution de r#m dépend de la microstructure. L'indice fragilisation f permet de mettre en évidence l'influence positive de la décomposition spinodale et de la précipitation de la phase G. L'utilisation de l'indice de fragilisation % permet de montrer que la précipitation de la phase implique une fragilisation par l'hydrogène plus élevée, malgré des quantités inferieures d'hydrogène absorbe - l'acier duplex a l'état de livraison, charge en hydrogène, présente la possibilité de récupérer complètement ses propriétés mécaniques grâce a un traitement thermique de revenu à basse température (< 250°C) - la fissuration par fatigue a l'air ne varie pas avec la fréquence (entre 10 et 50 Hz) ni avec la direction de charge (lt ou Tl). Les modifications microstructurales dans la ferrite après revenu a 475c ou a 800c modifient la vitesse de fissuration dans les stades ii et iii, mais pas sur le stade de seuil - la fissuration de l'acier duplex sous chargement d'hydrogène en conditions potentiostatiques dans l'eau de mer n'a pas lieu - la fissuration de l'acier duplex sous chargement en conditions potentiostatiques dans une solution aqueuse d'acide sulfurique a lieu avec des vitesse plus élevées dans les trois stades de propagation, car outre la fragilisation de la ferrite, il y a un début de fragilisation de l'austénite. L’importance de l'influence de l'hydrogène est différente suivant les valeurs de k. La formation des stries a toujours lieu dans l'austénite et dans la ferrite, avec une distance entre stries qui dépend de la vitesse macroscopique, du libre parcours moyen de l'hydrogène dans la ferrite et dans l'austénite et de la dimension de la zone plastique réversible.

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Uehara, André Yugou. "Fragilização por hidrogênio de parafusos cementados." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265279.

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Orientador: Itamar Ferreira
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Este trabalho tem por objetivo investigar a etapa de decapagem ácida e os processos de desidrogenação e retrabalho realizados durante a zincagem de parafusos quanto à fragilização por hidrogênio. Parafusos fabricados conforme a norma JIS B 1127 (1995), cementados, de 6 mm de diâmetro e 16 mm de comprimento de rosca foram organizados em 39 diferentes grupos. A decapagem foi avaliada quanto ao volume de ácido clorídrico (700 ml, 900 ml e 1000 ml) e presença, ou ausência, de inibidor para este ácido, utilizando tempos de decapagem de 15, 30, 45 e 60 minutos para cada condição de volume de ácido e inibidor utilizados. A desidrogenação foi avaliada utilizando parafusos decapados (solução: 1000 ml de ácido, ausência de inibidor e decapados por 15, 30, 45 e 60 minutos) e desidrogenados a uma temperatura de 1000C e tempo total de processo de 1, 2 e 3,5 horas. O retrabalho foi avaliado utilizando parafusos de 8 ?m de espessura de camada zincada, retrabalhados por 4 minutos em 700 ml de ácido, ausência de inibidor e 300 ml de água, avaliando as hipóteses do retrabalho único e duplo sem desidrogenação e do retrabalho único seguido de desidrogenação (1000C - 2 horas). Ensaios de pré-carregamento para a detecção da fragilização por hidrogênio foram realizados em parafusos que sofreram as preparações citadas, sendo o torque de ruptura avaliado nestes parafusos, assim como naqueles obtidos após o tratamento térmico. Análises química e metalográfica e ensaios de microdureza Vickers e tração, além de análise fratográfica por microscopia eletrônica de varredura (MEV) também foram realizados. A análise metalográfica revelou uma matriz ferrítica composta por grãos equiaxiais com carbonetos esferoidizados para o fio máquina, enquanto que o parafuso possui estrutura ferrítico-perlítica no núcleo e martensita revenida na camada cementada. Os ensaios de microdureza e de tração revelaram que o fio máquina e o parafuso possuem níveis de resistência mecânica dentro do esperado conforme as condições utilizadas, enquanto que não houve diferenças significativas entre os valores de torque de ruptura obtidos em ambas as situações analisadas. A etapa de decapagem ácida revelou que, nos grupos que não utilizaram inibidor, o número de falhas aumenta num primeiro momento com o aumento do tempo de decapagem, reduzindo após um determinado tempo de decapagem relacionado ao volume de ácido utilizado. O número de falhas sofre grande redução com a utilização do inibidor, porém mesmo a baixas concentrações de ferro, a utilização de maiores volumes de ácido associado a maiores tempos de decapagem aumentam o risco de fragilização. Apenas houve falha para a desidrogenação realizada a 1000C, por 1 hora, revelando a importância de adequados controles de temperatura, procedimentos de homogeneização e parâmetros de temperatura e tempo. Não houve falhas para o retrabalho revelando a importância de adequados procedimentos de retrabalho (tempo e solução) e de desidrogenação, enquanto que a análise da superfície de fratura revelou apenas os micromecanismos de fratura intergranular e dimples, sendo este último mais freqüentemente associado a regiões mais próximas ao núcleo, além da presença de trincas secundárias
Abstract: The main aim of this work is to investigate the effects on hydrogen embrittlement of bolts due to acid pickling, baking, and strip processes performed during zinc plating. Carburized bolts type "hexagon flange head tapping screws", with 6 mm of diameter and 16 mm of thread length were organized into 39 different groups. Acid pickling was evaluated using volumes of hydrochloric acid of 700 ml, 900 ml, and 1000 ml, presence, or absence, of acid inhibitor, and pickling periods of 15, 30, 45, and 60 minutes for each condition of acid volume and inhibitor used. Baking was evaluated using 1000C, and periods of 1, 2, and 3.5 hours for bolts that were subjected to acid pickling with a solution of 1000 ml of acid, absence of inhibitor, and pickling periods of 15, 30, 45, and 60 minutes. Strip was evaluated using bolts with zinc layer thickness of 8 ?m, stripped for 4 minutes in a solution of 700 ml of acid, absence of inhibitor, and 300 ml of water, performing the hypotheses of single and double strip without baking, and single strip followed by baking (1000C - 2 hours). Preloading tests for the detection of hydrogen embrittlement were conducted in bolts that were subjected to the preparations mentioned, while torsional tests were also conducted at these bolts, as well as in those obtained after heat treatment. Chemical and metallographic analysis, Vickers microhardness and tensile tests, and fractographic analysis using scanning electron microscopy (SEM) were also conducted. Metallographic analysis revealed a ferritic matrix composed of equiaxed grains with spheroidized carbides for the wire, while the bolts showed a ferritic-pearlitic microstructure at the center and tempered martensite at the hardened layer. Microhardness and tensile tests revealed that wire and bolts have strength levels as expected according to the conditions used, while no significant differences between the breaking torque values were obtained in both situations analyzed. Acid pickling revealed that in the groups, which did not use inhibitor, the number of failures increases at a first stage with increasing pickling periods, however it starts to decrease after a certain pickling period related to the volume of acid used. The number of failures is greatly reduced with the use of the inhibitor, but even at low concentrations of iron, the use of larger amounts of acid associated with longer pickling periods increases the risk of hydrogen embrittlement. Failures were observed only at 1000C - 1 hour as baking parameters, showing the importance of proper temperature controls, homogenization procedures, and temperature and time parameters. There were no failures related to strip, revealing the importance of adequate procedures for strip (period and solution used) and baking procedures as observed. The fracture surface analysis revealed only intergranular and dimples micromechanisms of fracture, where the latter being more often associated with regions closer to the core of the bolts, also showing the presence of secondary cracks
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica

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37

Boster, Connor M. Boster. "Metallurgical Characterization and Testing of Dissimilar Metal Welds for Service in Hydrogen Containing Environments." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524179509481363.

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38

Carvalho, Ícaro Zanetti de. "Fragilização por hidrogênio nos aços AISI 4340 (AMS 6414K e AMS 6415S) temperados e revenidos." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263642.

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Orientadores: Célia Marina de Alvarenga Freire, Itamar Ferreira
Dissertação (mestrado - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: O fenômeno da fragilização por hidrogênio no aço AISI 4340 foi investigado devido ao fato do mesmo ser um aço baixa liga de alta resistência bastante suscetível a este fenômeno. A análise foi feita por meio do ensaio de tenacidade à fratura por flexão baseado na norma ASTM E 399 - 09. A matéria prima utilizada foi fabricada segundo dois diferentes processos, sendo o primeiro pelo método convencional de fundição e o segundo pelo processo VAR (vacuum arc refining) de maneira a se obter uma liga com menores quantidades de impurezas. Corpos-de-prova foram retirados da posição L-C das ligas, temperados a 845 oC e revenidos a 3 diferentes temperaturas (350 oC, 400 oC e 500 oC). O carregamento de hidrogênio foi feito por meio de uma célula eletroquímica, onde os corpos-de-prova foram imersos numa solução de H2SO4 0,01 M com aplicação de uma densidade de corrente de 10 mA/cm2 e dois diferentes tempos de hidrogenação, de maneira a se obter dois níveis de contaminação. Após os ensaios, foram feitas fractografias dos corpos-de-prova ensaiados para cada condição de revenimento e contaminação por hidrogênio, sendo observadas as alterações nos micromecanismos de fratura para as diferentes condições. Os resultados obtidos no ensaio de tenacidade à fratura por flexão foram correlacionados ao micromecanismo de fratura em função da dureza e contaminação por hidrogênio. O aço AISI 4340 convencional nas condições de revenimento de 400 oC e 350 oC mostrou-se bastante susceptível à fragilização por hidrogênio, apresentando reduções da ordem de 10% e 20%, respectivamente, nos valores de tenacidade à fratura de corpos-de-prova contaminados. O mesmo não foi observado no aço AISI 4340 convencional temperado e revenido a 500 oC, que não sofreu fragilização devido à sua baixa dureza. O aço AISI 4340 VAR em todas as condições de revenimento apresentou-se muito menos susceptível ao fenômeno, não sendo evidenciadas variações expressivas nas tenacidades à fratura dos corpos-de-prova contaminados e nas superfícies de fratura resultantes
Abstract: The phenomenon of hydrogen embrittlement in AISI 4340 steel was investigated due to the fact that it is a high strength low alloy steel quite susceptible to this phenomenon. The analysis was done through the fracture toughness test by bending based on ASTM E 399-09. The material used was manufactured according two different processes, the first by conventional casting process and the second by VAR (vacuum arc refining) process in order to obtain an alloy with minor amounts of impurities. Specimens were removed from the position L-C of the alloy, quenched at 845 oC and tempered at 3 different temperatures (350 oC, 400 oC and 500 oC). The hydrogen loading was made by means of an electrochemical cell where the specimens were immersed in a solution of 0.01 M H2SO4 by applying a current density of 10 mA/cm2 and two different hydrogenation times, in order to obtain two levels of contamination. After the tests were performed fractographies of specimens tested for each condition of temper and contamination by hydrogen, with observed changes in the micromechanisms of fracture for the different conditions. The test results of fracture toughness by bending were correlated with the micromechanisms of fracture, the microstructure and hydrogen contamination. The conventional AISI 4340 steel under conditions of tempering of 400 °C and 350 °C proved to be very susceptible to hydrogen embrittlement, with reductions of 10% and 20%, respectively, on the values of fracture toughness of contaminated specimens. The same was not observed in conventional AISI 4340 quenched and tempered at 500 °C, which did not presented embrittlement due to its low hardness. The AISI 4340 VAR steel in all conditions of temper proved to be much less susceptible to the phenomenon, not showing significant variations in fracture toughness of the contaminated specimens and the resulting fracture surfaces
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica

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39

Oriol, Pierre. "Comportement des aciers à rails vis-à-vis de l'hydrogène : diffusion, perméation et fragilisation." Châtenay-Malabry, Ecole centrale de Paris, 1987. http://www.theses.fr/1987ECAP0041.

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Etude de la diffusion et de la perméation a l'hydrogène dans différentes nuances d'aciers à rail en fonction de la teneur en soufre, du sens de prélèvement des éprouvettes et du taux de corroyage. Étude de la fragilisation différée sur une nuance dure par suivi de l'émission acoustique en fonction du chargement en hydrogène. Examen de l'influence de l'hydrogène sur le comportement en traction des différentes nuances

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40

Mallick, Dwaipayan. "Hydrogen behavior in first and second generation of advanced high strength steels." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI052.

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Les aciers AHSS sont largement utilisés pour les caisses des véhicules, en raison de leurs bonnes propriétés mécaniques et de leurs capacités à réduire l'empreinte carbone. Toutefois, leur utilisation est limitée par leur sensibilité à la fragilisation par l'hydrogène (HE). La présente étude vise à comprendre l'influence de l'hydrogène sur quatre aciers AHSS : deux biphasés (DP), un phase complexe (CP) et un à plasticité induite (TWIP). Les résultats montrent une forte susceptibilité à l’HE pour les aciers DP et TWIP par rapport aux aciers CP. Le comportement de CP est attribuée à une microstructure plus homogène, une densité de piège plus petite (mais à énergie élevé) et une concentration en H plus faible. Dans les aciers DP, la forte densité de pièges à faible énergie et la forte absorption de H augmentent la susceptibilité à l’HE. Les dislocations et les joints de grains sont les principaux sites de piégeage pour tous ces aciers, ainsi que la cémentite dans les aciers CP et les particules AlN et l’austénite pour les aciers TWIP. Sous chargement mécanique, la désorption de l'hydrogène s’accélère avec l'expansion du réseau cristallin et les mouvements des dislocations (jusqu'à la limite d'élasticité), alors qu'elle diminue en raison de la génération de défauts dans la domaine plastique. Pour l'acier CP, l'hydrogène piégé fortement désorbe à l'UTS alors que dans l'acier TWIP, la génération de défauts libère l'hydrogène. Pour l’acier DP galvanisés, la couche de Zn se comporte une couche barrière à l’hydrogène sous polarisation fortement cathodiques, tandis qu'à potentiels cathodique plus faible, elle favorise la perméation de l'hydrogène en raison de sa dissolution
Advanced High Strength Steels (AHSS) are increasingly used as fabrication material for vehicle Body In White (BIW), owing to their superior properties and ability to reduce carbon footprint. However, its susceptibility to hydrogen embrittlement (HE) restricts the use of AHSS. The present study aims to understand the H influence on four commercial-grade AHSS steels, two Dual Phase (DP), one Complex Phase (CP), and one Twinning Induced Plasticity (TWIP) steel. Results show high HE susceptibility for DP and TWIP steel compared to CP steel. The superior HE resistance in CP steel was attributed to a more homogeneous microstructure, smaller yet stronger trap density, and lower H concentration. In DP steels, a high density of weak traps and high H uptake increased HE susceptibility. During charging, H preferentially adsorbed along the grain boundaries and interfaces for all steels along with grain interior in TWIP steels. Dislocations and grain boundaries were the main trap sites for all steels, along with cementite particles in CP steels and AlN particles and austenitic grain interior in TWIP steels. For all steels under stress, hydrogen desorption increased up to yield point due to lattice expansion and dislocation movement, whereas decreased in the plastic region due to defect generation. For CP steel, strongly trapped hydrogen desorbed at UTS whereas in TWIP steel, generation of deformation twinning released hydrogen. The study of the galvanized layer showed that at higher cathodic overpotential, the Zn layer behaved as a barrier layer protecting the steel, while at a lower potential, it increased the HE susceptibility due to Zn layer dissolution. Overall, CP steel was the most resistant steel to HE, followed by TWIP and DP steels

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Simoni, Leonardo. "Efeito da presença de depósito calcário formado durante a proteção catódica na absorção de hidrogênio e na fragilização pelo hidrogênio do aço API 5CT P110." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/149367.

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O processo de proteção catódica é amplamente utilizada na indústria do petróleo e gás para a prevenção contra a corrosão. Entretanto, devido às reações catódicas induzidas pelo potencial catódico aplicado pode ocorrer a formação de depósito calcário na superfície de componentes protegidos catodicamente em água do mar. Existe certa incerteza na literatura sobre o papel do depósito calcário na absorção de hidrogênio e consequentemente na fragilização pelo hidrogênio. Assim, o presente trabalho visa investigar sua influência a fim de contribuir para o melhor entendimento da participação dessa camada nesse fenômeno. Para isso, foram realizados testes de permeação eletroquímica de hidrogênio, de tração de baixa taxa de deformação (BTD) e de cronoamperometria no aço API 5CT P110 em três soluções diferentes: água do mar sintética (AMS), água do mar sintética sem Ca2+ e Mg2+ e NaCl 3,5%. Além disso, foram aplicados dois potenciais catódicos: -1000 mVECS e -1500 mVECS. Após o ensaio de tração de BTD e de cronoamperometria as amostras foram analisadas em MEV/EDS. A partir dos resultados obtidos verificou-se que o depósito calcário formado em AMS em -1000 mVECS é formado por uma fina camada inicial rica em Mg seguida de cristais de aragonita. A formação dessa camada aparentemente diminuiu o fluxo de hidrogênio no estado estacionário em comparação com as demais soluções avaliadas nesse mesmo potencial. Todavia, essa diminuição não resultou em uma mudança significativa na fragilização do material. O depósito calcário formado em AMS em -1500 mVECS mostrou-se poroso e pulverulento, apresentando principalmente Mg em sua composição. O fluxo de hidrogênio no estado estacionário e a fragilização do material em AMS em -1500 mVECS foi maior do que nas demais soluções nesse potencial. Um possível mecanismo para explicar o efeito do depósito calcário na absorção e na fragilização pelo hidrogênio foi proposto e indica a competição entre o fator superficial ocasionado pela formação do depósito calcário e a sobretensão em hidrogênio.
The process of cathodic protection is widely used in oil & gas industry to corrosion prevention. However, the cathodic reactions induced by the applied cathodic potential can lead to the calcareous deposit formation on the cathodically protected structure surface in sea water. There is uncertainty about the role of calcareous deposit on hydrogen uptake and consequently on hydrogen embrittlement. Hydrogen electrochemical permeations, slow strain rate and chronoamperometric tests were carried out in three different solutions: artificial sea water, artificial sea water without Ca2+ and Mg2+ and 3.5% NaCl solution. Besides that, two cathodic potentials were applied: -1000 mVSCE e -1500 mVSCE. After slow strain rate and chronoamperometric tests the samples were analyzed in SEM/EDS. According to the obtained results it was observed that calcareous deposits formed in artificial sea water at -1000 mVSCE consists on a thin Mg-rich inner layer and an outer layer of aragonite crystals. The deposit formation apparently decreased hydrogen flux at steady state in comparison with other solutions evaluated at the same potential. The calcareous deposit formed in artificial sea water at -1500 mVSCE was porous, powdery and mainly composed by Mg. The hydrogen flux at steady state and the embrittlement of the material were higher in artificial sea water at -1500 mVSCE than in other solutions at the same potential. A possible mechanism to explain the calcareous deposit effect on hydrogen uptake and on hydrogen embrittlement was proposed and it indicates the competition between the surface effect induced by calcareous deposit formation and the hydrogen overpotential.

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Kornegay, Cynthia E. "Impact fracture of austenitic stainless steels." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/50038.

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Industry is constantly searching for improved materials for use in highly demanding applications. The materials chosen must withstand a wide range of temperatures and extended exposure in aggressive environments, including hydrogen gas. Because of the risk of catostrophe if brittle failure occurs, careful material selection is imperative. Austenitic stainless steels may be a likely choice for hydrogen service because their behavior in high pressure hydrogen ranges from no apparent damage to relevent, but generally small ductility loss (13). Because of this Variation in behavior, a single category cannot be established to encompass all austenitic steels and studies must be performed on each type of steel to determine its behavior under specific circumstances. Two steels being currently under consideration for use in hydrogen are Armco 21-6-9 and Tenelon, both are fully austenitic stainless steels which may be used over a wide range of temperatures, including service at liquid nitrogen temperature.
Master of Science
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Fraga, Francisco Edson Nogueira. "Variaveis de influencia do teste G-BOP." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263151.

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Анотація:

Orientador: Roseana da Exaltação Trevisan
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Trinca induzida por hidrogênio é um dos defeitos mais graves que ocorrem em juntas soldadas de diversos aços. Esta falha mecânica ocorre com bastante freqüência na zona afetada pelo calor (ZAC) destes materiais. Com o desenvolvimento de novos aços, o risco da ocorrência de trincamento na ZAC tem se reduzido cada vez mais e passado a ocorrer com mais freqüência no metal de solda (MS). O teste G-BOP (Gapped Bead-on-Plate) destaca-se dentre os vários testes autodestrutivos pela grande aplicação em avaliar susceptibilidade de ocorrência de trincas de hidrogênio somente no cordão de solda. As principais vantagens deste teste são: baixo custo quando comparado a outros testes, simplicidade na execução e facilidade em quantificar trincas a frio no MS. Apesar de todas as vantagens, este teste tem sérias limitações e uma delas é o fato de não ser normalizado. Visando contribuir com informações que possam agregar maior confiabilidade e contribuir para a normalização do teste G-BOP, este trabalho teve como objetivo principal estudar de maneira sistemática e científica a influência das principais variáveis do teste G-BOP (dimensão do rebaixo, energia nominal de soldagem e temperatura de preaquecimento) sobre a variável de resposta, que é o percentual de trinca induzida por hidrogênio na seção transversal do metal de solda, As três variáveis foram estudadas segundo uma análise estatística de variância, identificando a influência individual de cada uma e a interação entre elas sobre os resultados do teste. Para o desenvolvimento experimental foi utilizado como material de base um aço ASTM A-285 grau C, como metal de adição, um arame tubular de classificação AWS E71T-1 e o 'CO IND. 2¿ como gás de proteção auxiliar. Para os níveis de cada uma das variáveis analisadas aqui, identificou-se que a energia nominal de soldagem e a temperatura de preaquecimento são variáveis que tem influência significativa sobre os resultados do teste G-BOP e que a variável dimensão do rebaixo não tem influência significativa. Identificou-se ainda que a interação entre estas variáveis também não apresenta influência significativa sobre os resultados do teste
Abstract: Hydrogen induced cracking (HIC) is a serious defect that occurs in welded joints of several steel types. This mechanical failure occurs frequently on the heat affected zone (HAZ). With the development of new steels the probability of HIC occurring on the HAZ has reduced, however it has started to occur on the weld metal (WM). The Gapped bead-on-plate test (G-BOP) stands out from several other self-restraint tests for its great application to evaluate HIC only on the weld metal. The main advantages of this test are: low cost, simple execution and crack quantification on WM. Despite its advantages, this test has a serious limitation that it is not normalized. To contribute to getting information that can add greater trustworthiness to G-BOP test and help to normalize it, the objective of this study is to evaluate the influence of the main variable of the G-BOP test (gap, welding heat and preheat temperature) in the output variable (HIC %). A variance analysis was used to identify the influence of these variables in the test results. For the experimental development the ASTM A-285 grade C steel was used as base metal as well as AWS E71T-1 flux core and 'CO IND. 2¿ shielding. It was concluded that the heat input and the preheat temperature have significant influence in the test result. The gap and the interaction between these variables don't have any influence in the test result
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia de Fabricação

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44

Alnajjar, Michella. "Corrosion properties of 17-4 PH martensitic stainless steel obtained by additive manufacturing." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEM035.

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Ce travail de thèse porte sur la corrosion de l'acier inoxydable à durcissement structural 17-4 PH élaboré par fabrication additive par fusion sélective laser (SLM).Nous avons montré que la microstructure de l'acier 17-4 PH fabriqué par SLM est ferritique, contrairement à l'acier corroyé qui a une microstructure martensitique typique. Ceci résulte des vitesses de refroidissement et de chauffage très élevées (105-106 K/s) qui empêchent la formation de l'austénite et conduisent à une rétention complète de ferrite δ issue de la solidification.Nous avons mené une étude comparative de corrosion électrochimique à l'aide de courbes de polarisation anodiques dans des solutions chlorurées acides. Le matériau SLM présente une meilleure résistance à la corrosion généralisée que le matériau corroyé. Ce résultat est lié à l'absence d'inclusions MnS dans le matériau SLM. Au contraire, dans le matériau corroyé, la dissolution des inclusions MnS conduit à une redéposition d'espèces riches en soufre sur toute la surface, ce qui déstabilise le film passif.Nous avons également mené une étude de la fragilisation par l'hydrogène. Cette étude a montré une sensibilité plus forte du matériau SLM, qui peut s'expliquer par la différence de microstructure, en particulier la taille grains. Le matériau SLM, ferritique, présente une fissuration sous-critique transgranulaire, dont l'initiation est pilotée par le niveau de contrainte et la quantité d'hydrogène introduite dans le matériau. Au contraire, dans l'acier corroyé, martensitique, la fissuration sous-critique suit les anciens joints austénitiques. On montre par ailleurs que son initiation nécessite un minium de déformation plastique
This PhD thesis focuses on the corrosion properties of 17-4 PH precipitation hardenable stainless steel obtained by additive manufacturing, specifically by Selective Laser Melting (SLM).It was shown that the microstructure of 17-4 PH steel fabricated by SLM was ferritic, in contrast to the typical martensitic microstructure of wrought 17-4 PH steel. This was correlated to the high cooling and heating rates (105-106 K/s) experienced during SLM that suppressed the δ ferrite to austenite transformation and retained the δ ferrite until the end of fabrication.A comparative electrochemical study was conducted on both steels. It was found that the SLM-ed steel had superior general corrosion resistance than the wrought steel. This was attributed to the absence of MnS inclusions in the SLM-ed steel. In contrast, in the wrought material, the dissolution of the MnS inclusions resulted in the redeposition of sulphur-rich species all over the surface, which contributed to the destabilization of the passive film.A hydrogen embrittlement study was also conducted. It was found that the SLM-ed ferritic steel was more susceptible to hydrogen embrittlement than the wrought martensitic steel. The difference in microstructure, specifically the grain size, played a major role in this difference in behavior. In the SLM-ed ferritic steel subcritical cracking was transgranular and its initation was governed by the stress level and the amount of hydrogen introduced into the material. On the other hand, in the wrought martensitic steel, subcritical cracking was along the prior austenitic grain boundaries and it was shown that its initiation required at least a small amount of plastic deformation

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Rosado, Diego Belato. "Comparação do efeito da fragilização por hidrogênio em aços com resistência à tração acima de 1000 MPa." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/37374.

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Este trabalho tem por objetivo avaliar os efeitos do hidrogênio em três diferentes tipos de aços de alta resistência mecânica. São descritos os fenômenos de introdução, difusão e aprisionamento de hidrogênio (H) dentro dos metais, em conjunto com os diferentes tipos de danos provocados devido à presença do hidrogênio. Os materiais de estudo são aços da família Advanced High Strength Steels (AHSS): aços Dual Phase (DP 1000 e DP 1200) e aço Martensítico (M 190). A introdução de hidrogênio nos materiais foi realizada através de carregamento catódico, o qual é representativo para as condições industriais a que se destinam. De modo a avaliar a influência do H nas propriedades mecânicas dos aços, os seguintes ensaios foram propostos: ensaio de carregamento com H, para determinar o conteúdo total de H (saturação) e conteúdo de H difusível (suscetibilidade a fragilização); ensaio de tração ao ar, para determinar a tensão no final da região elástica e resistência à tração na região do entalhe e ensaio de tração com carga constante em ambiente hidrogenado, para avaliar os efeitos provocados pela presença do H e determinar o patamar abaixo do qual o H não apresenta efeito crítico sobre o material. Os efeitos provocados pela aplicação de diferentes densidades de correntes (0,2 – 1,0 mA/cm²) foram avaliados nos ensaios de quantificação de H difusível. Conforme os resultados obtidos todos os aços apresentaram perdas na resistência mecânica à tração quando em ambiente hidrogenado, ou seja, sofreram fragilização por H. Os aços DP 1200 e M 190 (de microestrutura predominantemente martensítica) foram fortemente afetados, conforme evidenciado pela notável queda nos valores de tensão necessários para provocar a falha. Por outro lado, o aço DP 1000, de menor resistência mecânica, demonstrou menor suscetibilidade à fragilização, o que é atribuído a menor permeabilidade do H na microestrutura austenítica.
This work aims to evaluate the effects of hydrogen in three high- strength steel grades. The phenomena of hydrogen (H) entry, transport and trapping inside the metals, together with the different types of damages due to the presence of hydrogen are presented. The study materials are a range of AHSS steel grades: Dual Phase Steel (DP 1000 and DP 1200) and Martensitic Steel (M 190). The hydrogen entry was performed by cathodic charging, which is suitable for industrial applications. In order to evaluate the influence of H on the steel mechanical properties, the following tests were done: H charging, to measure total H content (saturation point) and diffusible H content (embrittlement susceptibility); uniaxial tensile test of uncharged samples to determine notched tensile strength values and the strength levels at the end of elastic region and constant load tensile testing carried out in hydrogen environment, to determine the threshold values where hydrogen has an effect on the material. DP 1200 and M 190 were strongly affected by H pre-charging, as shown by the significant drop in stress required to break them. On the other hand, DP 1000 showed a lower embrittlement susceptibility, which is attributed to its lower mechanical strength. The current densities effects (0.2 up to 1.0 mA/cm²) were evaluated during H charging to measure diffusible H content. All steels showed a drop in the tensile strength i.e. experienced hydrogen embrittlement. Steels with higher tensile strength, as DP 1200 and M 190, showed a much bigger drop that is related to the favorable characteristics of martensitic microstructure regarding to the hydrogen permeability and diffusivity.

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Gayton, Clément. "Mécanismes de fragilisation de l’acier inoxydable super-martensitique X4CrNi16-4 Virgo™38 : Effets couplés des traitements thermiques et des milieux corrosifs contenant Na2S ou H2S." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEM004/document.

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Ce travail de thèse porte sur l’étude de divers mécanismes de fragilisation d’un acier inoxydable supermartensitique 16Cr-4Ni à basse teneur en carbone (Virgo™38) utilisé pour la fabrication des compresseurs centrifuges produits par GE Oil&Gas.Il a été montré que la microstructure fine, polyphasée et morphologiquement très complexe de cet alliage était sensible aux conditions de traitement thermique. Notamment, la proportion et la répartition de l’austénite de réversion, la présence de carbure de chrome et la ségrégation intergranulaire d’éléments fragilisant tel que le phosphore ont été mis en évidence suite à plusieurs traitements thermiques. La ségrégation du phosphore aux joints de grain (SPJG) est l’un des mécanismes entrainant la fragilisation du Virgo™38 sous certaines conditions de traitement thermique.La présence d’austénite de réversion n’entraine pas seulement une amélioration de la ténacité de l’alliage mais également le piégeage de l’hydrogène dans cette phase. Etant donnée la grande instabilité mécanique de l’austénite, sa transformation sous contrainte provoque la libération de cet hydrogène piégé et ainsi une surconcentration locale en hydrogène. La fragilisation par hydrogène est le deuxième mécanisme entrainant la fragilisation du Virgo™38 étudié dans cette thèse.Les mécanismes mis en jeu lors de la formation de l’austénite de réversion conduisent à la répartition hétérogène des éléments d’alliage. L’une des conséquences de cette répartition hétérogène est la corrosion sélective de l’une ou l’autre des phases de l’alliage en fonction du pH de l’environnement et de la charge appliquée. La dissolution préférentielle est le dernier mécanisme abordé
This PhD thesis is focused on the study of embrittlement mechanisms in a 16Cr-4Ni low carbon supermartensitic stainless steel (Virgo™38) used for the construction of rotating parts of centrifugal compressors produced by GE Oil&Gas.It is shown that the morphologically complex multiphase microstructure of this alloy is very sensitive to the heat treatment conditions. In particular, the fraction and repartition of retained austenite, the presence of chromium carbides and the phosphorous grain boundary segregation (PGBS) are evidenced consecutive to several heat treatments. PGBS is one of the mechanisms leading to brittle failure of Virgo™38 after specific heat treatments.The presence of retained austenite is not only beneficial for toughness but also leads to hydrogen trapping in this phase. Due to the mechanical instability of retained austenite, its transformation under applied stress leads to the release of trapped hydrogen into newly formed martensite and thus to a local overconcentration of hydrogen. Hydrogen embrittlement is the second mechanism studied in this report.Mechanisms involved during the formation of retained austenite lead to the heterogeneous repartition of alloying elements (partitioning). One of the consequences being the selective dissolution of one or the other phase of the alloy as a function of the pH of the environment and of the load applied. Preferential dissolution is the third mechanism studied

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Ramírez, Mario Fernando González. "Influência da microestrutura nas propriedades mecânicas e na fragilização por hidrogênio em um aço microligado." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-19072013-170730/.

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A tecnologia dos aços microligados para transporte de gás natural e petróleo tem sido pressionada pelo descobrimento das novas jazidas e o aumento da demanda no mundo. As solicitações ambientais e de resistência mecânica são os parâmetros para o desenvolvimento de aços de alta resistência baixa liga para o transporte de gás e petróleo a menor custo e de forma segura. Neste contexto esta pesquisa investiga, em um aço microligado para tubos API 5L X80, o efeito das transformações de fase obtidas por resfriamentos controlados na fratura induzida por hidrogênio Hydrogen Induced Cracking-(HIC) e nas propriedades mecânicas. Os testes de HIC foram realizados no material como recebido, na espessura da chapa submetida a resfriamentos contínuos e em amostras do material tratadas de forma a simular as regiões de grão grosso da zona afetada pelo calor (GGZAC). Segundo o ciclo de resfriamento, os aços microligados têm microestruturas complexas, como é caso do aço microligado em estudo, onde sua microestrutura, estudada em trabalhos anteriores, é formada principalmente por ferrita, bainita, perlita e microconstituinte austenita/martensita (AM). A morfologia, tamanho, quantidade e distribuição dos produtos de transformação na chapa mudam as propriedades do aço. Esses fenômenos são de grande interesse tecnológico em aços microligados para a fabricação de tubos soldados para o transporte de gás e petróleo, tanto quando a solda é realizada em campo como também durante o encurvamento por indução; aqui as propriedades mecânicas do tubo decorrentes do processo de fabricação termomecânico podem ser degradadas pela ação do aquecimento e dos resfriamentos experimentados na zona afetada pelo calor (ZAC), principalmente na região de GGZAC. A simulação dos ciclos térmicos para o estudo da HIC na espessura da chapa foram realizados em CP austenitizados a 900ºC e submetidos a resfriamentos contínuos no dilatômetro de têmpera. Para simular os ciclos térmicos com resfriamentos controlados focados na GGZAC e a seguir obter CP de tamanho adequado para testes de tração e Charpy, foi necessário fazer os tratamentos térmicos a 1300ºC e resfriamentos contínuos em um simulador termomecânico e dilatômetro Gleeble. O maior tamanho da amostra tratada termicamente neste último equipamento permitiu extrair amostras para avaliar as propriedades mecânicas e a HIC do material, pois as diferentes regiões da ZAC em uma solda real são restritas e não permitem este tipo de ensaios em uma região específica da ZAC. Os resultados permitiram identificar a suscetibilidade de cada microestrutura produto da transformação da austenita na espessura da chapa, sendo a região central da chapa a mais sensível ao hidrogênio no aço como recebido e quando tratado a baixas taxas de resfriamento de 0,5°C/s após austenitizado a 900°C. As bandas grosseiras formadas por estruturas de maior dureza que a matriz na região central diminuíram a resistência à HIC. Da mesma forma nos corpos de prova que simulam a região GGZAC, a fratura induzida pelo hidrogênio foi localizada na região central da espessura embora apresente bainita e ferrita acicular. A falha possivelmente se deve aos elementos remanescentes segregados nesta região central e partição de carbono para os sub contornos de grão da bainita e ferrita que cresceram a partir a austenita primária. As inclusões e precipitados, segundo seu tipo, forma e localização na microestrutura, participam ou não da nucleação e propagação da trinca, sendo a posição mais crítica quando localizadas dentro das estruturas bandeadas. Não foi observada a nucleação de trincas na presença de hidrogênio em precipitados de Nb e Ti.
The technology of microalloyed steels for the transportation of natural gas and oil has been pressed by the discovery of new deposits and the increased demand in the world. Environmental requests for safety and ever increasing mechanical strength are the parameters for the development of high strength low alloy steels for transporting gas and oil at lower cost and safely. In this context, this research investigates, in a microalloyed steel pipe API 5L X80, the effect of phase transformations obtained by controlled cooling on the behavior when loaded with hydrogen - Hydrogen Induced Cracking - (HIC) and in the mechanical properties. HIC tests were performed on as-received material, on samples extracted from the thickness of the plate and subjected to continuous cooling and on samples of the material treated to simulate the coarse-grained regions of heat affected zone (CGHAZ). According to the cooling cycle, the microalloyed steels have complex microstructures: in the steel under evaluation its microstructure, studied in a previous work, consists mainly of ferrite, bainite, pearlite and austenite/martensite constituent (AM). The morphology, size, quantity and distribution of the products of transformation change the properties of plate steel. These phenomena are of great technological interest in microalloyed steels for the fabrication of welded tubes for the transport of gas and oil, when the welding is performed in the field as well as during hot bending; here the mechanical properties of the tube from the process of thermomechanical fabrication can be degraded by the action of heating and cooling experienced in the heat affected zone (HAZ), mainly in the region of CGHAZ. Simulations of thermal cycles for the study of HIC on sheet thickness were performed in coupons subjected to austenitization at 900ºC followed by continuous cooling in the dilatometer. To simulate the thermal cycles with controlled cooling, focused in the CGHAZ, and getting suitable sample sizes for tensile testing and Charpy, it was necessary to austenitize at 1300ºC followed by continuous cooling using the thermal and thermomechanical simulator in a Gleeble dilatometer. Samples heat treated in this equipment were suitable to evaluate the mechanical properties and the HIC of the material for different regions of HAZ, while a real weld would not have enough material to allow this type of testing on a specific region of HAZ. The results showed the susceptibility of each microstructure product of austenite transformation and of the position on the plate thickness. The central region of the plate was more sensitive to hydrogen in the steel as-received and when treated at low cooling rates of 0.5°C/s after austenitization at 900°C. The bands formed by coarse structures of greater hardness than the matrix in the central region decreased the resistance to HIC. Likewise in coupons that simulate the CGHAZ region, the fracture induced by hydrogen was located in the central thickness line, even when the microstructure were bainite and acicular ferrite. Failure there was possibly due to remnants of segregated elements in this central region and carbon partition to the subboundaries of the bainite and ferrite grain that grew from the primary austenite. Inclusions and precipitates, according to their type, shape and location in the microstructure, participating or not in the nucleation and propagation of the crack, were more critical when located within the banded structures; crack nucleation in the presence of hydrogen was not observed at Nb and Ti precipitates.

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Christopher, Petersson. "Erosion-Corrosion experiments on Steels in liquid lead and Development of Slow Strain Rate testing rig." Thesis, KTH, Kärnenergiteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-261611.

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Forot, Clément. "Application de la perméation d’hydrogène vers la prédiction des risques de fissuration interne des aciers." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10348.

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L'objectif de ce travail est de prédire les risques de fissuration par H2S d'aciers au carbone à très haute limite d'élasticité utilisés en environnement pétrolier. Nous nous intéressons aux conditions de sévérité modérées, caractérisées par des teneurs faibles mais non nulles en H2S dans le milieu corrosif. Dans ces environnements, le chargement en hydrogène dans les aciers est lent, et les temps d'incubation avant apparition de fissures internes de type HIC peuvent donc être longs. En complément des essais standards de tenue à la fissuration des aciers, il est donc important de pouvoir disposer de méthodes rapides et fiables d'évaluation des risques de fissuration. La principale technique expérimentale mise en oeuvre est la perméation électrochimique d'hydrogène. Elle est mise à profit afin d'étudier le chargement, la diffusion et le piégeage de l'hydrogène dans différents aciers à haute limite d'élasticité en environnement faiblement concentré en H2S. En complément des essais de perméation, nous effectuons une étude de la fissuration assistée par l'environnement dans différentes conditions de pH et de PH2S. Ces essais permettent d'abord de vérifier l'évolution de la cinétique de fissuration interne en fonction des conditions environnementales. Dans le même temps, nous réalisons des mesures de la quantité d'hydrogène absorbée par le métal, en distinguant les parts d'hydrogène libre, piégé réversiblement et irréversiblement. La confrontation entre les données de diffusion et de piégeage issues des essais de perméation, et des données directes de fissuration et de quantités d'hydrogène absorbé permet l'établissement de seuils de concentrations critiques en hydrogène. Ces seuils sont ensuite utilisés afin de mettre en place une approche empirique prédictive de la fissuration HIC dans les aciers
The work of this thesis applies to flexible pipelines, which are used as risers or flowlines in offshore production. More specifically, it is dedicated to study the risks of hydrogen embrittlement of carbon steel wires used as armors if flexible pipes. The study is focused on low H2S containing medium inducing slow hydrogen entry in steels, thus, potentially long incubation times before embrittlement becomes effective. The first goal of this work is to study the entry, diffusion and trapping of hydrogen into different grades of carbon steel in low H2S concentration environment. The permeation technique will be used, as well as immersion tests of variable duration with characterization of the crack process. Analysis of permeation transients gives information on hydrogen diffusion and hydrogen trapping into steels in function of experimental conditions (pH, PH2S). Immersion tests will be performed complementary to permeation tests in various conditions of pH and PH2S. We verify the cracking evolution with environmental conditions. We also quantify the lattice hydrogen, the reversibly and irreversibly trapped hydrogen absorbed by the materials. Then, using both diffusion properties from permeation tests and cracking data from immersion experiments, we set up a predictive approach to link the risks of H2S cracking for each steel grade in function of the severity of the environment. Applying this method should also allow to establish faster and more reliable comparisons of the hydrogen induced cracking resistance of different steel grades. It should be used as complimentary tool for qualification purposes

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SantAnna, Alexandre Magno de Souza. "Efeito da hidrogenação em solução NS4 nas propriedades do aço API 5L X-65." Universidade do Estado do Rio de Janeiro, 2010. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=1287.

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O comportamento do aço API 5L X65 foi estudado em solução sintética NS4. Estudou-se o efeito da hidrogenação ao aplicar um potencial catódico nas amostras de tração e de impacto Charpy. Estas amostras foram imersas em solução saturada de sulfato de cobre para evitar a saída de hidrogênio, sendo posteriormente foram testadas à tração e ao impacto. Algumas amostras foram tratadas superficialmente por shot peening antes de serem hidrogenadas. Após todos esses tratamentos foi medida a tensão residual nas amostras por tensometria de raios X. Adicionalmente, foram levantadas curvas de polarização anódica e catódica do aço na solução NS4 desaerada com nitrogênio gasoso e simulado o equilíbrio químico desta solução. As superfícies de fratura das amostras foram analisadas por microscopia eletrônica de varredura.
The behavior of API 5L X-65 steel immersed in synthetic solution NS4 was studied. The changes caused on the effect of the hydrogen when applying a cathodic electrical potential on tensile and impact samples were also studied. The samples were immersed into saturate solution of copper sulfate to avoid the hydrogen desorption and after that, were performed tensile and impact tests. Some samples were submitted to shot peening process before suffering the hydrogen action. After these treatments the residual stress was determined by X ray tensometry. Additionally, cathodic and anodic polarization curves were obtained in NS4 solution deaerated with nitrogen gas. Moreover, the chemical balance of NS4 solution was performed. The fracture surfaces of the samples were analyzed using scanning electron microscopy.

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Дисертації з теми "Steel Hydrogen embrittlement Testing"

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