Dissertations / Theses on the topic 'Acier inoxydable super duplex'
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Da, Silva Craidy Pedro. "Interactions Hydrogène-Microstructure-Propriétés Mécaniques dans les Composants en Acier Inoxydable Super Suplex." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAI041.
Full textThe increasing demand for energy requires the exploration of oil and gas at deeper water locations and on more severe conditions. These production systems have demanded the use of forged equipments made of higher strength steel grades, such as austenitic-ferritic (duplex) stainless steels. These components are more prone to exhibit loss of ductility and general mechanical performance caused by hydrogen generated e.g. by cathodic protection. Duplex stainless stainless steels components present a vast history of hydrogen damage at low temperatures, due to hydrogen derived from various sources. Even being this kind of damage fairly recurring, various related information remains to be elucidated, due to the complex interaction of hydrogen with the microstructure and localized character of hydrogen generation and transportation in the material. The present work aims to improve the physical understanding of the interaction between hydrogen and the microstructure as well as the effects of different hydrogen charging procedures on the mechanical properties of forged components made of the super duplex stainless steel grade UNS S32750.The development of such understanding involves the evaluation of the effects of hydrogen on the mechanical properties of the material through tensile tests in different hydrogen-rich environments. Based on results of slow-strain rate tensile tests, a quantitative relationship between embrittlement caused by gas hydrogen and cathodic charging is proposed, and possible effects of dislocation-assisted hydrogen transportation and embrittlement are discussed. Quantitative and qualitative descriptions of the hydrogen transportation, including analysis of the effects of different microstructures and diffusion paths, and of its position in the lattice and in the microstructure (hydrogen segregation to traps) are proposed. These descriptions are achieved considering results of different testing techniques: permeation tests, thermal desorption spectroscopy, time-of-flight secondary ion mass spectroscopy and neutron scattering
Poinsot, Jocelin. "Influence des éléments cuivre et tungstène sur les mécanismes de corrosion localisée des super-duplex." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCK013.
Full textSuper duplex stainless steels (SDSS) are interesting engineering materials, due to their generally high corrosion resistance combined with high strength. They are widely used in various industrial sectors, such as oil & gas (pipelines and storage tanks), desalination (evaporators and pumps), geothermal, pollution control (scrubber) and pulp and paper (digester and bleaching reactors) industries.In this PhD thesis, the influence of the addition of copper and tungsten in SDSS on their localised corrosion resistance (pitting) was investigated. Three alloys studied were: UR2507, UR2507Cu (1.6 %wt. Cu) and UR2507W (0.6%wt. Cu and 0.6%wt. W).The thickness and chemical composition of the passive film formed on the three alloys after optimised surface preparation was first investigated by means of X ray photoelectron spectroscopy and Auger electron spectroscopy before and after immersion in highly concentrated NaCl solutions. Pitting corrosion resistance was then investigated in NaCl-based media using the critical pitting temperature testing method combined with the electrochemical microcell technique (capillary diameter of about 300 microns) and potentiostatic pulse technique (PPT). Local CPT measurements were used to compare the resistance of the three different alloys to pitting while PPT enables to compare the size of the pits formed. In addition, pitting potentials were measured in samples with 5 cm² area in solutions of different NaCl concentrations and temperatures. These measurements are closer to the real using conditions of the alloys.It was showed that copper and tungsten effects on localised corrosion resistance in SDSS depend on the using media (T, [Cl-]) and the initiation and start of the propagation phases can also be influenced by parameters not linked to composition such as local pH and surface conditions (cold-work layer)
Ballésio, Sébastien. "Caractérisation et modélisation de la tenue à la fatigue et à la corrosion de l’acier inoxydable super duplex 2507 obtenu par fabrication additive LP-DED." Electronic Thesis or Diss., Institut polytechnique de Paris, 2024. http://www.theses.fr/2024IPPAE011.
Full textThe main objective of this thesis is to propose an in-depth study of the "Super duplex 2507 stainless steel - Laser Powder-Direct Energy Deposition (LP-DED) process" combination and to establish an approach for optimising the manufacturing process (with or without heat treatment) in terms of mechanical and electrochemical properties. Several steps are being taken to achieve this objective.Firstly, criteria for assessing the quality of the material deposited by additive manufacturing are defined. This led to the optimisation of printing parameters using the LP-DED BeAM Mobile-004 machine and SAF2507 super duplex stainless steel powder.Next, the impact of the process on the microstructure is assessed, as well as the impact of various heat treatments applied to the LP-DED raw material. A comparison with a forged steel of the same grade is also proposed, enabling the differences and similarities between conventional processes and metal additive manufacturing to be put into perspective.Uniaxial tensile tests, hardness tests, pitting corrosion tests and fatigue test campaigns are then carried out on the various materials obtained. This experimental phase enables the influence of microstructure to be studied and variations in the properties examined to be observed.Finally, a model is proposed to describe the fatigue behaviour observed in super duplex 2507 stainless steel. This model takes account of the two-phase nature of the material, with each phase exhibiting a specific behaviour. The proportion of each phase is integrated in an attempt to reflect the contrasts observed during self-heating fatigue testing campaigns as a function of the material's microstructure.This thesis contributes to a better understanding and optimisation of the LP-DED additive manufacturing process for super duplex 2507 stainless steel, by highlighting the importance of the microstructure on the mechanical and electrochemical properties of the material
Kchaou, Yacine. "Etude comparative de la tenue mécanique des joints soudés des réservoirs sous pression de deux aciers inoxydables super austénitique et duplex." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2015. http://www.theses.fr/2015ESMA0005/document.
Full textThis thesis focused on the study of low cycle fatigue and crack growth of welded joints of superaustenitic (Alloy28) and Duplex (UNS S32550) stainless steels. The effect of the presence of the welded joint in the structure was also examined.The first part of this work was to study the monotonous and cyclic behavior of the base metal and weld metal of each stainless steel. The behavior laws of each material were identified at room temperature.Low cycle fatigue tests at different levels of deformation were performed on stainless steels and their welded joints. The results indicate that the fatigue life of welded joints is lower than the base metal. The analyses of damage mechanisms show that the short life of welded joints is attributed to the acceleration of the initiation phase.Finally, crack propagation tests in Alloy28 stainless steel show that load ratio has an effect on the crack growth rate due to the closure phenomenon by roughness and plasticity. The crack growth rate in the weld metal is very similar to that of the base metal. This is due to the compensation of various effects such as the roughness, the residual stress and the closure phenomenon. The duplex stainless steel does not present load ratio effect on the crack growth rate. The crack growth rates of the weld metal of the duplex stainless steel are also comparable to those of the base metal
Massol, Karen Vogt Jean-Bernard Foct Jacques. "Influence de la microstructure et de l'environnement sur le comportement en fatigue d'aciers inoxydables duplex alliés à l'azote." [S.l.] : [s.n.], 2001. http://www.univ-lille1.fr/bustl-grisemine/pdf/extheses/50376-2001-3-4.pdf.
Full textXu, Yun. "Contribution à l'étude de l'endommagement par fatigue d'alliages biphasés : fatigue-torsion oligocyclique d'un acier inoxydable duplex." Saint-Etienne, EMSE, 2005. http://www.theses.fr/2005EMSE0035.
Full textThe aim of the research is to include/understand the cyclic damage mechanisms in fatigue-torsion. The materials chosen in this work were thoroughly analysed in uniaxial fatigue tests and the comparisons between the results obtained with these two modes of request are herein included. In the single-phase steels and , a new core cracking was observed. Cracking along the the test-material axis has a beneficial effect and can often induce a rather astoundingly fast progressive rupture. With regard to the mechanisms of propagation in volume, observations of the face of the cracks were equally carried out and the results show that coalescence on the surface does not accelerate the damage. In the aged duplex steel at 475°C during 200h, our investigation was focused on the role of each of the individual phases present throughout the deformation process. At low level deformation, the majority of the cracks started in the grains of the -phase and, the fraction of the cracks which makes however part in the -grains, increases with the increase in the amplitude of subsequently imposed deformation. Our published results were an upgrading on the already existent barrier model, originally proposed by Jacques STOLARZ. The brittleness of the aged duplex steel provokes an instability on the symmetry level of the of the maximum constraints in the two deformation directions. An obvious asymmetry can occur under certain conditions, such as the temporary halt, or the interruption and resumption of cycling. According to our observations, a non-null average constraint can improve the lifespan in fatigue-torsion
El, Bartali Ahmed. "Apport des mesures de champs cinématiques à l’étude des micromécanismes d’endommagement en fatigue plastique d’un acier inoxydable duplex." Ecole Centrale de Lille, 2007. http://tel.archives-ouvertes.fr/docs/00/25/47/32/PDF/These_ElBartali.pdf.
Full textThe aim of this work is firstly to develop an in-situ microscopy device to perform surface damage observations at the microstructural scale on standard duplex stainless steel fatigue specimen during low-cycle fatigue tests, and secondly, to acquire digital images regularly during cycling to analyse damage thanks to kinematical fields calculated by digital image correlation (DIC) technique. Surface observations allow to identify and to follow development and localisation of cyclic plastic strain, to identify microcrack initiation sites, and to follow propagation of these cracks at the surface. These observations combined with EBSD analysis enable to identify activated slip systems in each phase. The relief measurements by interferometric profiler allow to characterise the morphology of the slip markings appeared at the surface. The random surface texture necessary to DIC is obtained by a lightly electrochemically etching of the specimen. Fields measured highlight strain heterogeneities at grain scale, cumulated plastic strain levels and their dispersions in each phase. They allow also to detect the probable microcrack initiation sites, very before their observation. The study shows the complementarity of the various techniques used, in particular the interest of field measurements at the microstructural scale, towards the understanding of low-cycle fatigue damage in a two-phased material such as a duplex stainless steel
David, Charles. "Influence de la déformation plastique sur la résistance à la corrosion de l'acier inoxydable lean duplex UNS S32304." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAI026/document.
Full textLean duplex stainless steels are alloys basically composed of iron, chromium and nickel in which two cristallographic phases coexist (austenite - γ and ferrite - α). These steels present high mechanical properties and corrosion resistance, and find their main applications in the offshore oil exploration and water desalinization sectors. Despite the excellent properties, the effect of plastic strain induced by forming on the corrosion resistance of these materials is yet to be understood, and may represent an improvement lever for these alloys. This study had thereby the aim of determining the microstructure parameters related to plastic strain and that might have an impact on the oxidation reaction of the metal and on the hydrogen evolution reaction (HER), which are often connected to corrosion phenomena of metals in acidic environments. The role of the emergence of slip steps, which are the result at the surface of the sliding of dislocations inside the metal while it deforms plastically, were also studied. Specimens for tensile testing made from UNS S32304 lean duplex stainless steel were strained by interrupted uniaxial tensile testing at different levels ranging from 0% to approximately 20%. A group of specimens with and another group without presence of slip steps on the surface were produced. A study of the plasticity mechanisms of the lean duplex stainless steel was carried out. It mainly involved characterizations of structures of dislocations, internal stresses and slip steps. It distinguished the ferritic and austenitic phases. Corrosion rates (oxidation) of the metal and HER taking place at its surface were studied by electrochemical technique in acidic chloride medium. It was demonstrated that, in the absence of slip steps, plastic strain has no detectable effect on its corrosion resistance in the conditions of the study. Nevertheless, slip steps have shown a strong impact on corrosion rates. That was related to a modification of HER kinetics. For low stain levels (up to approximately 3%), corrosion rates as well as HER kinetics strongly increased (up to 4 times), and then decreased and reached values similar to the ones of the unstrained state at approximately 10% of strain. Tests on monophasic steels having chemical compositions similar to those of each phase of the lean duplex stainless steel have confirmed this important role played by steps. The same has been observed by a local electrochemical technique based on microcapillaries. After confrontation with a simulation based on literature, the analysis points to an explanation involving the electron work function of the surface presenting slip steps and to the role played by the emergence of (111) plans
Maetz, Jean-Yves. "Évolution de la microstructure d’un acier inoxydable lean duplex lors du vieillissement." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0008/document.
Full textLean duplex stainless steels are austeno-ferritic steels with lower nickel and molybdenum contents, developed in the late 90's. Considering mechanical properties, corrosion resistance and cost of raw material, this family is an interesting alternative to standard austenitic stainless steels, which currently represent two thirds of stainless steel production. However, lean duplex steels are relatively recent and their thermal stability has been relatively little studied, especially during long term aging. In this study, the microstructural evolution of a lean duplex steel 2101 was studied during isothermal aging at temperatures between 20 °C and 850 °C, from few minutes to several months. Aging kinetics were followed by thermoelectric power measurements (TEP), from which aged states were selected to be characterized by electron microscopy and atom probe tomography. At intermediate temperatures of 350 - 450 °C, Fe-Cr demixing and precipitation of Ni-Mn-Al-Si-Cu occur in the ferrite despite the low nickel content of this grade, leading to an increase in the TEP. For higher temperatures, at about 700 °C, the mechanisms which govern the different microstructural evolutions have been described by a multi-scale approach: the nucleation and growth of M23C6 and Cr2N, observed from few minutes of aging and the σ phase precipitation, observed for longer aging time. The latter is accompanied by a transformation of δ ferrite in γ2 secondary austenite, and by the partial transformation of austenite into martensite during cooling. The effect of different phases on the TEP of the lean duplex steel can be qualitatively described during aging by a rule of mixture
Massol, Karen. "Influence de la microstructure et de l'environnement sur le comportement en fatigue d'aciers inoxydables duplex alliés à l'azote." Lille 1, 2001. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2001/50376-2001-3-4.pdf.
Full textLes essais effectué à l'air ont montré une dépendance du comportement des matériaux en fonction du niveau de déformation. Pour de faibles sollicitations, l'austénite accommode pratiquement à elle seule la déformation plastique. Par contre, dès que des niveaux de déformation trop important sont atteints, la ferrite devient de plus en plus active. La présence d'un milieu corrosif a entraîné une diminution générale des durées de vie des matériaux, l'acier contenant 0. 4wt% d'azote montrant tout de même une meilleure résistance. De même, alors que le matériau ne contenant que 0. 25wt% d'azote a montré une très grande sensibilité à un vieillissement de 200 heures à 475ʿC, la résistance du deuxième alliage n'a pas été modifiée. Les performances de l'acier à 0. 4wt% d'azote ne sont pas directement dues à cette forte teneur en azote mais plutôt à l'effet indirect qu'elle entraîne qui est l'augmentation de la quantité d'austénite au sein du matériau. Ceci constituera nos principales conclusions
Evrard, Pierre. "Modélisation polycristalline du comportement élastoplastique d’un acier inoxydable austéno-ferritique." Ecole Centrale de Lille, 2008. http://tel.archives-ouvertes.fr/docs/00/31/60/73/PDF/These_Evrard.pdf.
Full textUntil now, the plastic behaviour of an austenitic-ferritic stainless steel (DSS) has been modelled using phenomenological models. Unfortunately, these models do not take into account the biphased character of the material, and the polycrystalline character of each phase. Furthermore, a large experimental data base is necessary in order to identify model parameters. These results motivated the development of a biphased polycrystalline model. Two models are used and extended in order to take into account both polycrystalline phases. A single crystal law describes each austenitic and ferritic phase. Model parameter identification needs only two simple tests and literature results. Both models predict correctly the first hysteresis loops for a tension-compression/torsion test and the yield surface evolution. Then, the cyclic softening is explained from transmission electronic microscopy analyses. It is observed that both phases contribute to cyclic softening. However, in a first approach, only the rearrangement of dislocations in hard and soft zones in ferritic grains is modelled. The results show that the new model predicts well cyclic hardening and softening and the stabilized hysteresis loops for uniaxial and biaxial non-proportional cyclic loading. Finally, kinematic fields obtained by a microstructure computation are compared to the experimental ones. After a monotonic tension test, a good agreement is obtained between simulated and experimental kinematic fields, which is not the case after a tension-compression test
Ridlova, Martina. "Comportement en tribocorrosion des aciers inoxydables AISI 321 et Duplex 22-05 en environnement aqueux." Châtenay-Malabry, Ecole centrale de Paris, 2003. http://www.theses.fr/2003ECAP0903.
Full textSeddouki, Abbass. "Endommagement en fatigue plastique oligocyclique à température ambiante d'aciers inoxydables duplex austéno-ferritiques type Z2 CND 22-05 alliés à l'azote." Lille 1, 1994. http://www.theses.fr/1994LIL10093.
Full textEvrard, Pierre. "Modélisation polycristalline du comportement élastoplastique d'un acier inoxydable austéno-ferritique." Phd thesis, Ecole Centrale de Lille, 2008. http://tel.archives-ouvertes.fr/tel-00316073.
Full textDeux modèles de la littérature sont étendus à l'acier duplex. Les comportements des grains austénitiques et ferritiques sont décrits via des lois de plasticité cristallines. L'identification des paramètres matériau ne demande que deux essais mécaniques simples et des données de la littérature. Les modèles proposés rendent bien compte des premières boucles d'hystérésis d'essais de traction-compression/torsion non-proportionnels et de l'évolution des surfaces de plasticité.
Puis, l'adoucissement cyclique a été expliqué à partir d'analyses MET. Celles-ci ont montré que les deux phases participent à l'adoucissement cyclique. Cependant, dans une première approche, seul le réarrangement des dislocations en zones dures et molles dans les grains ferritiques a été modélisé. Les résultats montrent que le nouveau modèle prédit bien le durcissement et l'adoucissement cyclique, et les boucles d'hytérésis au cycle stabilisé.
Enfin, les champs cinématiques issus d'un calcul de microstructure ont été comparés à ceux mesurés (El Bartali07). Une bonne concordance est observée suite à un trajet de traction monotone, l'écart est plus important pour un trajet de traction-compression.
Naser, Hasan. "Développement de micro-composites architecturés en aciers inoxydables duplex : élaboration, microstructure et propriétés mécaniques." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI024/document.
Full textThe use of duplex stainless steel (DSS) grades for structural applications is considered as one of the most significant advances impacting the construction sector. This is because of their high mechanical properties coupled with interesting functional properties such as corrosion resistance or even the low thermal conductivity compared to carbon steels. Due to their complex microstructure and interaction between the phases, DSS have a significant potential for unique properties. A better understanding is needed to give the possibility to obtain break through properties and to provide the possibility to design tailor-made, architectured DSS for specific applications. In this work we proposed a different approach from that used until now to understand the behavior of DSS. The strategy adopted in this work was a top-down strategy in which at least two bulk metals with well known behavior and properties are mechanically alloyed by Severe Plastic Deformation (SPD). This proposed strategy served two main objectives: i) enhancing the properties by microstructure refining down to sub-micron scale ii) elaborating a material model for understanding the DSS behavior obtained by the conventional metallurgical methods. The first objective of this work was, therefore, the implementation of a methodology of manufacturing using SPD technique by co-drawing. This technique will allow obtaining an ultra-fine microstructure of 316L/430LNb composites. One of the challenges met during our study was the significant inter-diffusion during heat-treatment step necessary during processing preventing by consequence further refining. An optimization investigation was carried out to account the role of this inter-diffusion for 316L/430LNb couple. Multi-scale micro-composites have been then obtained. In this work, we showed the limitation of this process in terms of microstructure refining. A rationalization of these limits was given by studying the thermo-kinetics of both micro-composites and bulk materials. In parallel with the microstructural evaluation, the mechanical behavior of these new micr-composites was examined. In order to provide a more in-depth explanation of the plastic behavior of our composites, in situ tensile test using high energy X-ray synchrotron have been performed
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.
Full textThis 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
Tresallet, Damien. "Evolution des microstructures au cours d'un recuit dans un acier inoxydable superduplex : caractérisation et modélisation." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAI088.
Full textSuperduplex stainless steels are high-performance stainless steel grades that combine great specific mechanical properties with an excellent resistance to pitting and stress corrosion cracking. The design of new grades with improved properties requires the control of the microstructure and phase transformations occurring during the manufacturing process. Particularly, the rolling steps impart to the alloy the so-called duplex structure, a fine layered microstructure made of two phases, ferrite (δ) and austenite (γ). After the cold-rolling step, an annealing treatment performed at a temperature close to 1100°C give the alloy desired properties. At this temperature, both phases are present in comparable proportions in the alloy, however the layered microstructure evolves towards a more equiaxed and thicker structure within a few tens of seconds. The mechanisms leading to these microstructural evolutions during annealing was studied in this work. A model Fe-Cr-Ni-Mo-N superduplex stainless steel was produced by a semi-industrial process and supplied in the form of cold-rolled sheets. Its microstructure was studied after isothermal annealing treatments performed within a temperature range of 1060-1180°C up to 300 s. The phase fractions reached the thermodynamic equilibrium during the first tens of seconds of the temperature steady state. A global thickening of the microstructure and a local thinning of the bands were identified. The local thinning was found located at the grain boundaries emerging at austenite-ferrite interfaces similarly to the thermal grain boundary grooving theory, it may also induce fractioning of the phases. Microstructure coarsening was also evidenced by a quantitative analysis. These two models describe the evolution of ideal morphologies due to capillarity. However, the complex morphology of the phases of the superduplex alloy give rise to morphological heterogeneities during annealing. The low energetic austenitic twin boundaries Σ3 (<111>, 60°) are not affected by thermal grooving. However, differences in grain boundary energy do not explain all the observed heterogeneities, and the morphology of the interfaces in their initial state has proved to be predominant. Through a collaboration, a phase field numerical simulation tool was upgraded to model the evolution of austenitic/ferritic interfaces of various morphologies during annealing. On the one hand, the splitting of a cylindrical particle by grain boundary grooving was found faster the one of a plate. On the other hand, the grain boundary grooving creates additional curved interfaces subject to coarsening. The double interaction of grain boundary grooving and coarsening leads to a rapid evolution of the microstructure. The interaction of neighboring grain boundaries can locally stabilize an interface, but the microstructure coarsening continues due to the curvature differences that exist between interfaces of a same band and those of adjacent bands
Salazar, Daniel. "Étude du partage de la plasticité cyclique d'un acier duplex par microscopie à force atomique." Thesis, Lille 1, 2008. http://www.theses.fr/2008LIL10004/document.
Full textIn order to increase the understanding of monotonic and cyclic plastic deformation mechanisms in multiphase alloys, an intensive research task has been carried out on a Duplex Stainless Steels (DSS-50%α-50%γ) using Atomic Force Microscopy (AFM). After monotonic deformation, AFM investigations of the surface reveal that this technique is especially promising for the plasticity studies of DSS. It allows high detailed characterisation of different types of slip lines, depending of their morphology, dimensions and the analysed phase, austenite or ferrite. Concerning the Low Cycle Fatigue behaviour at low strain range, contrary to earlier works, the comparison of the surface topography between two alloys differing by their ferrite hardness (annealed and aged), suggests that the macroscopic cyclic behaviour of the annealed DSS is a consequence of the mutual contribution of the two phases. Performing interrupted fatigue tests at high strain range, High-Rugged (HR) areas were identified in ferritic grains and near the α/γ interfaces. The formation of HR areas is a consequence of the high surface activity (extrusions) in an austenitic neighbour grain, the relative crystallographic “compatibility” between α/γ grains and the phase distribution. In addition, the close interaction between the two phases was still evidenced, this time as a transfer of the plastic activity from austenite to ferrite. It turns out that, taking into account the whole results set obtained in this work, the cyclic plasticity of the duplex stainless steels could be explained like a progressive contribution of the activity in the two phases and their interactions. Therefore, the utilisation of different regimes depending of the deformation levels, supported by the individually activity or passivity of each phase, appears to be a simplified explanation that does not illustrate the real cyclic behaviour of this material
El, Bartali Ahmed. "Apport des mesures de champs cinématiques à l'étude des micromécanismes d'endommagement en fatigue plastique d'un acier inoxydable duplex." Phd thesis, Ecole Centrale de Lille, 2007. http://tel.archives-ouvertes.fr/tel-00254732.
Full textFardoun, Farouk. "Etude de la déformation plastique cyclique des aciers inoxydables austénitique, ferrique et duplex, par analyse des boucles d'hystérésis : contraintes internes et effectives." Lille 1, 1997. http://www.theses.fr/1997LIL10157.
Full textGardin, Elise. "Etude des interactions bactéries-surfaces et des effets sur la passivation des aciers inoxydables." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEC009.
Full textStainless steels have a high corrosion resistance thanks to the formation of an oxide layer at their surface, commonly referred to as the passive film, which is a few nanometers thick and composed mainly of Fe(III) and Cr(III) oxides and/or hydroxides. However, in aggressive environments, the stability of the oxide layer can be compromised, which can initiate corrosion phenomena (localized or general). For example, in presence of microorganisms, and more particularly of bacteria, bacterial adhesion and biofilm formation at the surface can lead to the initiation and/or the acceleration of corrosion processes: this is referred to as biocorrosion. In this work, we first characterized the oxide layer formed at the surface of 2304 duplex stainless steel by a coupling of fine surface analysis techniques (XPS and ToF-SIMS). We showed differences in the chemical composition of the surface on each phase of the duplex alloy. We then characterized the surface of the duplex alloy during the adhesion of marine aerobic bacteria Pseudoalteromonas NCIMB 2021 in marine medium by a coupling of microscopic characterization techniques (epifluorescence microscopy, SEM and AFM), fine surface analysis techniques (XPS and ToF-SIMS) and electrochemical techniques (open circuit potential monitoring, anodic and cathodic polarization curves). In particular, we showed that biofilm formation is accompanied by modifications of the oxide layer
Gutier, Patrick. "Pulvérisation cathodique magnétron en condition réactive et propriétés mécaniques de revêtements duplex d'acier inoxydable enrichis en azote, carbone et oxygène." Vandoeuvre-les-Nancy, INPL, 2000. http://www.theses.fr/2000INPL042N.
Full textThis work deals with the synthesis, the physico-chemical and mechanical caracterisation of coatings obtained by cathodic magnetron sputtering of a metallic austenitic stainless steel target in different argon - reactive gas (nitrogen, methan or oxygen) mixtures. The metastable solid solutions which are nitrogen, carbon or oxygen supersatured, as weIl as the ceramic compound of oxide type (Fe, Cr, Ni)₃O₄, with their different crystalline or amorphous structures are studied by means of the main diffraction techniques of structural analysis and physical methods of chemical analysis. The second part of this work aims to point out the complete mechanical properties of the different coatings and composite (coating + substrat). The intrinsic properties of the different coatings were first studied in relation with the elaboration parameters and structural properties. Vickers indentation as well as single pass and triboscopic multipass scratch testing were then performed on the three type of N, C, 0 doped coatings, in order to establish a relation between the brittleness or ductility and the tribological behaviour (friction, wear)
Marin, Raphaël. "Étude de la précipitation de la phase σ dans un acier super austénitique." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0132.
Full textImproving the corrosion resistance of industrial stainless steels ingots remains a scientific challenge. During ingot casting, chemical heterogeneities at the micrometer scale can arise and lead to the formation of chromium and molybdenum rich intermetallic precipitates that lower the corrosion resistance by removing these elements from the matrix. As-cast ingots exhibit σ-phase in the interdendritic region. The aim of this thesis work was to study the formation mechanism of σ phase with real solidification conditions and to study the impact of the microsegregation on the phase transformation during solution heat treatment. The characterization of samples elaborated with a Quenching Directional Solidification (QDS) set-up helped us to determine establish the solidification path, the phase transformations areas for the solidification conditions carried out and the σ-phase transformation mechanism of the steel. The complementarity of microstructural and chemical characterizations led to the conclusion that the (σ + γ2) precipitates present in the as-cast ingot are inherited from the microsegegation of molybdenum in the liquid during solidification and come from the eutectoid decomposition of the ferrite formed in the solidification interval. We also identified the complex dissolution sequence of the (σ + γ2) precipitates and the quantities that govern the slow dissolution kinetics. Thus, the interdendritic spacings, precipitates size σ + γ2) and molybdenum microsegregation in primary austenite inherited from solidification appear to be the main quantities
Kubecka, Petr. "Etude du comportement d'alliages passivables, acier duplex et alliage fer-nickel, soumis a l'action combinée du frottement et de la corrosion." Châtenay-Malabry, Ecole centrale de Paris, 1998. http://www.theses.fr/1998ECAP0584.
Full textRuel, Fiona. "Contribution électrochimique à l’étude de la corrosion sous contrainte des aciers inoxydables lean duplex en milieu purement chloruré et sous présence de sulfure d’hydrogène." Thesis, Saint-Etienne, EMSE, 2014. http://www.theses.fr/2014EMSE0743/document.
Full textLean duplex stainless steels, with low content of nickel and without molybdenum, represent an economic alternative for desalting plants and petroleum industry. For these uses, steel have the particularity to be exposed to very aggressive environments inducing phenomenon of Stress Corrosion Cracking as chlorides, hydrogen sulphur, high temperatures or acids.This study is divided in two parts dedicated to two different environments. The first part is devoted to chloride middles and the second to hydrogen sulphur middles. In both parts, the understanding of phenomenon linked to the stress corrosion cracking of lean duplex is studied on the grade steel S32304, then is compared to the behaviour of grade steels S32202 and S32101. The topics treated in this report are notably the influence of boiling environments on the cracking resistance of stainless steels, the mechanism of unpassivation and selective dissolution of lean duplex, the different modes of cracking in presence of hydrogen sulphur, and the initiation of stress corrosion cracking assisted by hydrogen sulphur
Rytirova, Lenka. "Etude de la dégradation par l'hydrogène des aciers micromaillés et duplex : influence de la microstructure." Châtenay-Malabry, Ecole centrale de Paris, 2006. http://www.theses.fr/2006ECAP1028.
Full textPetroleum and natural gas systems can be contaminated with aqueous H2S. This environment is very aggressive to the steels used for the transport and processing of these products. Hydrogen absorption into steel may result, and provokes hydrogen induced cracking(HIC) in the absence of applied stress. In the presence of applied or residual stress, the failure process can occur by sulphide stress cracking (SSC) or stress oriented hydrogen induced cracking (SOHIC). The resistance of steels is closely related to the microstructure features: non-metallic inclusions, hard phase constituents, banded structures etc. This thesis summarizes results of HIC and SSC resistance of pipelines steels: two carbon micro alloyed steels (X52 and X60 according to API 5L Specification) and one 225 duplex stainless steel (austenite – ferrite microstructure). Materials have been tested according to NACE TM 0284 (HIC) and TM 0177 - Method A (SSC). To obtain detailed information about material behaviour in the presence of hydrogen, electrochemical permeation tests were performed as well. This method lets know the hydrogen diffusivity in these materialsand the hydrogen trapping. Some permeation tests were followed by vacuum outgasing at 600°C, to obtain information about irreversible trapping. The different tests have been achieved in as-received state (AR, after rolling) and after a laboratory heat treatment (HT, quenching and tempering). Influence of samples taking orientation has been also examined. Microstructure and fracture surfaces of broken SSC specimens analysis was performed by means of optical metallography and scanning electron microscopy
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.
Full textThis 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
Badji, Riad. "Influence des traitements thermiques à haute température sur l'évolution de la texture et de la microstructure des soudures d'acier inoxydable duplex 2205." Phd thesis, Université Paris-Nord - Paris XIII, 2008. http://tel.archives-ouvertes.fr/tel-00806333.
Full textSamih, Youssef. "Thermomechanical surface treatments of austenitic stainless steels and their effects on subsequent nitriding during “Duplex” treatments." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0100/document.
Full textOptimizing the surface microstructure and properties is very important to obtain high performance behaviour. Applying appropriate mechanical and thermochemical treatments has been the prime objective of metallurgists. More recently, and particularly for the stainless steels, the Plasma Nitriding was found to be an efficient technique for enhancing the hardness and wear resistance. However, as the nitriding temperature is about 500 °C, the formation of nitrides on the surface leads to a decrease of the corrosion resistance of these alloys. Recent works have shown that using a mechanical pre-treatment allows to decrease the treatment temperature and duration, and also to enhance the nitrogen diffusion within the stainless steels surfaces. In the present work, performances of different Duplex treatments (mechanical + thermochemical) are studied. The Surface Mechanical Attrition Treatment (SMAT), cold rolling and the High Current Pulsed Electron Beam (HCPEB) are used as surface activators prior to plasma nitriding of stainless steels. Before studying the effect of surface activation on the nitrogen diffusion, the effect of the different SMAT parameters (balls size, balls nature, treatment duration … etc.) on the microstructure is analysed. A new technique based on the notion of Geometrically Necessary Dislocations (GND) is used to depict the thickness of the different SMAT-induced layers and compare the effect of the processing parameters. Then, comparative analysis of the results obtained after nitriding of mechanically deformed samples leads to quantify the effect of the different Duplex treatments. X-Ray Diffraction, Secondary Electron Microscopy associated with Electron BackScattered Diffraction (EBSD), hardness measurement and chemical composition analysis by Glow Discharge Optical Emission Spectroscopy (GD-OES) showed the importance of the surface microstructure and deformation state on the nitrogen diffusion
Lechartier, Audrey. "Influence de la transformation martensitique induite par la déformation sur le comportement mécanique d’aciers inoxydables duplex." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI107/document.
Full textDuplex stainless steels offer an attractive combination of high mechanical properties, low thermalconductivity and a relatively low cost. They are increasingly used as structural materials such as inthe construction sector as concrete reinforcement bars, where both high strength (Rm > 900 MPa)and high elongation to failure (A% > 15 %) are required. This thesis aims at improving the strength/ elongation compromise by developing new duplex stainless steel compositions experiencing a wellcontrolledmartensitic transformation induced by plasticity (TRIP effect). The optimisation of thiscompromise has required a good understanding of the transformation mechanisms and of plasticdeformation associated with each phase : ferrite (BCC), austenite (FCC) and martensite (BCC).The influence of martensitic transformation on mechanical behavior has been studied in four duplexgrades of variable austenite stability as a function of their chemical composition. The influence ofmultiphase microstructure on martensitic transformation kinetics has been determined by makingthree alloys respectively representative of a duplex grade and its two constituents (austenite andferrite). Using multiple characterization techniques at different scales has allowed determiningboth the transformation mechanisms and its kinetics as a function of strain, giving thus accessto the influence of transformation on the mechanical behavior. The study of kinematic fields hashighlighted the impact of the martensitic phase on the distribution of deformations. Finally, theuse of a mechanical model taking explicitly into account the phase transformation has allowed theduplication of the mechanical behavior of a duplex stainless steel
Zhang, Huayu. "Contribution à l'optimisation de la teneur en azote des aciers inoxydables austeno-ferritiques économiques par l'étude du comportement en corrosion à l'aide de sondes locales." Thesis, Dijon, 2011. http://www.theses.fr/2011DIJOS046.
Full textDuplex stainless steels (DSS) are highly important engineering materials, due to their generally high corrosion resistance combined with high strength and moderate alloy cost (lower nickel and molybdenum content). They are widely used in various industrial sectors. DSS have a complex microstructure with comparable volume of austenite and ferrite. Due to differences in chemical composition between austenite and ferrite, a heterogeneous passive film is formed on both phases. In addition, due to differences in mechanical properties, a heterogeneous stress field may be generated in metallic grains. Under certain conditions, these differences may also yield formation of a heterogeneous passive film. In this work, the influence of long-term ageing in chloride-containing media by on the chemical composition of the passive film was first studied by means of XPS and Auger at the microscale. The corrosion behaviour of some duplex stainless steels was then determined from CPT tests (determination of the critical pitting temperature). Results were analysed taking into account information obtained previously. After ageing, the thickness and the ratio Cr/Fe are significantly increased. The chloride distribution in the passive film was heterogeneous. It was related to the microstructure and the residual strain field. It was shown that this distribution modifies the electrochemical behaviour of samples. The corrosion behaviour was then analysed from local polarization curves and CPT tests. Metallurgical criteria for pitting were proposed
Ba, Djiby. "Contribution à l'effet des éléments d'alliage sur la résistance à la corrosion de nuances duplex exposées à des environnements simulant leur marché d'application par le biais d'approches locales." Thesis, Dijon, 2014. http://www.theses.fr/2014DIJOS060.
Full textDuplex stainless steels (DSS) are characterized by a two-phase structure comprising a mixture of ferrite and austenite. The proportion between the two phases is usually about 50%. They are increasingly used in the chemical, petrochemical, nuclear, marine and paper, mainly because of their excellent mechanical properties coupled with good resistance to pitting corrosion (low grade nickel and molybdenum). The austenite having a different chemical composition than the ferrite, a heterogeneous film is formed on the surface of duplex stainless steels. Furthermore, the two metallic phases having different mechanical properties, a field of heterogeneous stress is generated in the grains. Under certain conditions, these differences may also yield formation of a heterogeneous passive film. In this work, we study the effect of alloying elements on the physico-chemical properties of the passive film and behavior pitting corrosion before and after ageing in chloride media for a reference surface that meet certain criteria ie a smooth surface free from any defects (no hardened layer .. low roughness). The physicochemical properties of the film are studied using Auger and XPS analysis at the microscale. The corrosion behavior of duplex alloys was then determined from CPT tests (determination of the Critical Pitting Temperature). The results before ageing have shown that the passive film is homogeneous on a macroscopic scale and that pitting corrosion appear to be related to the grain size and crystallographic texture described by GOS. After ageing, surface analysis shows a strengthening of passivity by thickening of the passive film and the ratio Cr/Fe are significantly increased which has the effect of improving behavior pitting alloys. Metallurgical criteria for pitting were proposed
Srisrual, Anusara. "Caractérisation photoélectrochimique d'oxydes thermiques développés sur métaux et alliages modèles." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENI012/document.
Full textHigh Temperature Corrosion (HTC), in various and severe atmospheres, of continually more elaborated (composition, micro–structure) metallic alloys, is a rather complex industrial and scientific topic. PhotoElectroChemistry (PEC) acquired a special place in the characterization of physico–chemical and electronic properties of the highly heterogeneous oxidation layers formed in HTC. Through studies of model but industrially representative samples (duplex stainless steel, Ni–base alloy 690), this work presents the development and validation of an experimental set–up allowing for the first time to use the whole set of PEC techniques at the mesoscopic level (typically 30 µm), as well as the validation of an original model of photocurrent energy spectra, developed at SIMaP, allowing to well describe, and accurately fit the latter spectra, and thus yielding, notably, precise bandgap values for the semiconducting components of the thermal scale
Badyka, Romain. "Influence des éléments d'alliage sur la cinétique de vieillissement de la ferrite d'aciers inoxydables austéno-ferritiques moulés." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMR072/document.
Full textCast austenitic-ferritic stainless steels are used in primary circuit of 2nd generation nuclearpower plants. At operating temperature (285 °C - 325 °C), evolution of mechanical properties isobserved due to the phase transformations occurring within the ferrite: spinodal decomposition (SD)leading to the formation on a Fe rich phase (α) and a Cr rich phase (α ') and the precipitation of the G-phase at α/α' interfaces. This evolution of the mechanical properties can be prohibitive for thecomponents. If it is well known that the steel composition plays an important role on the evolution ofthe properties (steels less rich in Ni and Mo are less sensitive to aging), the role of solute elements asNi, Mo and Mn on the aging kinetics is not yet known so as the contribution of the G-phase on thehardening during the thermal aging. In this study, the aging kinetics of the ferrite of some austenitic-ferritic stainless steels with or without Mo and model alloys with tuned compositions have been studied by atom probe tomography (APT) and by micro hardness measurements. This works answered the three following questions: - Quantification of the contribution of both spinodal decomposition and G-phase precipitation on hardening of the ferrite: combination of hardening models and data obtained with APT permitted to show that G-phase precipitation is clearly the main contributor to ferrite hardness increase at early stage of ageing in Mo-bearing steels. This is due to the high number density of G-phase particles. In Mo-free steels which have ten times less G-phase particles, contributions of both spinodal decomposition and G-phase precipitation are similar. In both cases, when coarsening of G-phase particles occurs and SD is well developed, SD contribution becomes larger. - Influence of Ni, Mo and Mn on aging kinetics: The study of model alloys with tuned composition has shown that only Ni plays a role on SD by enhancing the decomposition. Mn is a key element for the precipitation of G-phase particles at α/α' interfaces. - Efficiency of regeneration heat treatment at 550 °C: an alternative to component replacement is to perform a heat treatment at higher temperature in order to restore the properties of the components. The heat treatments performed permitted to entirely restore the mechanical properties of Mo free steels and partially the properties of Mo bearing ones. This is due to the presence of undissolved G-phase particles in the case of Mo bearing alloys. In each case, SD was totally dissolved