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1
Wang, Yongqing. "Aluminide coatings on Fe-9Cr-1Mo steel synthesized by pack cementation for power generation applications : a dissertation presented to the faculty of the Graduate School, Tennessee Technological University /." Click to access online version, 2006. http://proquest.umi.com/pqdweb?index=89&did=1260818241&SrchMode=1&sid=1&Fmt=6&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1255459401&clientId=28564.
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Rannou, Benoît. "Slurry coatings from aluminium microparticles on Ni-based superalloys for high temperature oxidation protection." Phd thesis, Université de La Rochelle, 2012. http://tel.archives-ouvertes.fr/tel-00839790.
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Because of their good mechanical resistance at high temperature, Ni-based superalloys are used for aero-engine and land-based turbines but undergo "dry" oxidation between 900 and 1500°C. These materials are thus coated with nickel-aluminide coatings (BC). An additional thermal barrier coating (TBC) is generally applied in the hottest sections of the turbines (T>1050°C) to lower the impact of the temperature on the substrate. In the framework of the European research programme "PARTICOAT", this PhD work was focused on the growth mechanisms of a full protective coating system (BC+TBC) in a single step process, using a water-based slurry containing a dispersion of Al micro-particles to satisfy the European environmental directives. The rheological and physico-chemical characterizations showed the slurry stability up to seven days. After depositing the latter by air spraying, a tailored thermal treatment resulted in a nickel-aluminide coating (β-NiAl) similar to the conventional industrial ones but through an intermediate Al liquid phase stage. Simultaneously, the oxidation of the Al micro-particles brought aboutthe formation of a top alumina "foam" (PARTICOAT concept). After a validation step of the mechanisms involved in pure Ni substrate, the extrapolation of the process to several Ni-based superalloys (René N5 (SX), CM-247 (DS), PWA- 1483 (SX) and IN-738LC (EQ)) revealed different coating compositions and microstructures. A particular attention was therefore paid onto the effect of alloying elements (Cr, Ta, Ti) as well as their segregation in the coating. The high temperature behaviour of the coated samples has been studied through isothermal oxidation (1000h in air between 900 and 1100°C) and showed that the oxidation and interdiffusion phenomena ruled the degradation mechanisms. Besides, the electrodeposition of ceria before the application of the PARTICOAT coating allowed to strongly limit interdiffusion phenomena and stabilized the nickel aluminide coating.
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Priest, Matthew. "Synthesis of reactive element-modified aluminide coatings on single-crystal Ni-based superalloys by a pack cementation process a thesis presented to the faculty of the Graduate School, Tennessee Technological University /." Click to access online, 2009. http://proquest.umi.com/pqdweb?index=26&did=1760523421&SrchMode=1&sid=1&Fmt=6&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1254926883&clientId=28564.
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Mollard, Maël. "Elaboration de systèmes barrière thermique par barbotine : comportement du nickel et de ses superalliages revêtus en oxydation cyclique à haute température." Phd thesis, Université de La Rochelle, 2012. http://tel.archives-ouvertes.fr/tel-00839920.
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Les superalliages base nickel sont couramment utilisés dans les parties chaudes des turbines aéronautiques et de production d'énergie. Les températures employées, supérieures à 900°C, nécessitent de concevoir des revêtements protecteurs pour lutter contre les phénomènes d'oxydation. Les revêtements couramment utilisés, composés pour la plupart de la phase β-NiAl, permettent de retarder les phénomènes de dégradation en développant une couche d'alumine. Dans les sections les plus chaudes, une barrière thermique composée de céramique, associée à un système de refroidissement interne complètent le dispositif de protection en permettant d'abaisser la température effective au niveau du substrat métallique.Ces revêtements sont cependant onéreux et utilisent de nombreux produits polluants. Les travaux de cette thèse, qui s'inscrivent dans le cadre du projet européen Particoat, se proposent d'élaborer un système barrière thermique en une seule étape reposant sur l'application d'une barbotine à base aqueuse comprenant des microparticules d'aluminium, suivi d'un traitement thermique approprié. L'aluminium contenu dans les sphères devient liquide puis réagit avec le substrat pour former une couche d'intermétallique riche en aluminium par diffusion à l'état solide. Simultanément les coquilles des sphères s'oxydent pour former une structure mousse en surface du substrat qui va conférer au système son isolation thermique. La cohésion des deux parties est assurée par l'oxyde thermique qui se forme à la surface du revêtement inter métallique. Les mécanismes mis en jeu lors des différentes étapes, ont été étudiés sur un substrat modèle, le nickel, ainsi que sur trois superalliages industriels (René N5, PWA 1483 et CM-247). Les revêtements ainsi élaborés ont été testés en condition d'oxydation isotherme et cyclique entre 900 et1100°c pour le nickel et entre 1000 et 1100°C pour les superalliages revêtus. L'ensemble montre une bonne résistance du système barrière thermique élaboré par barbotine.
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Villemiane, Arnaud. "Comportement mécanique d'alliages pour couches de liaison de barrière thermique par microindentation instrumentée à haute température." Thesis, Vandoeuvre-les-Nancy, INPL, 2008. http://www.theses.fr/2008INPL112N/document.
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Les systèmes barrières thermiques protégeant les aubes de turbine sont des multicouches constitués d’une couche céramique isolante appliquée sur un superalliage par l’intermédiaire d’une couche de liaison qui, dans les systèmes actuels est à base de NiAl(Pt). Pour en comprendre et décrire le comportement thermomécanique, il est nécessaire de connaître le comportement de chaque couche, en particulier celui de la couche de liaison dont le rôle est critique. Nous avons employé une technique originale, la microindentation instrumentée à chaud (jusqu’à 850°C), pour obtenir des informations sur le comportement mécanique de matériaux de couches de liaison. Il a fallu d’abord fiabiliser le dispositif pour minimiser les effets d’oxydation et caractériser la stabilité thermique pour s’assurer de la validité et la reproductibilité des résultats. Un second volet a consisté à mettre en place une méthode de traitement de données et une méthode d’analyse inverse des résultats associant une approche analytique et une simulation de l’essai par éléments finis. Les essais menés sur des matériaux massifs élaborés sous forme de couples de diffusion pour explorer une large gamme de compositions ont permis de déterminer la loi de comportement élastoviscoplastique du composé NiAl(Pt) sous forme [bêta] et sous forme martensitique. Des propriétés mécaniques ont été également été déterminées sur les composés NiAl(Ru) et NiAl(Zr) envisagés pour des systèmes futurs. L’influence des divers éléments (Al, Pt et Ru) a pu ainsi être mise en évidence. Finalement des essais ont été effectués sur des couches de liaison de barrière thermique et les résultats corrélés à ceux obtenus sur matériaux massifsThermal barrier systems, which protect turbine blades, are multilayers constituted of an insulating ceramic layer applied on a metallic bondcoat itself in contact with the superalloy substrate. A widely used bondcoat is composed of a NiAl(Pt) compound. In order to understand and describe the thermomechanical behaviour of such systems, it is required to know the mechanical behaviour of each layer, in particular that of this bondcoat whose role is critical for maintaining the integrity of the systems. In this study, we have employed an original technique – high temperature instrumented microindentation, up to 850°C – to extract information on the mechanical behaviour of bondcoat materials. A preliminary phase consisted in improving the experimental procedure - in particular to minimise oxidation phenomena - and in characterising the thermal stability of the equipment at high temperature to ensure the reliability, validity and reproducibility of the results obtained. We have then developed a systematic data treatment and an inverse problem analysis combining analytical approaches and a FEM simulation of the experiment to extract a mechanical behaviour law of the materials investigated. Tests performed on bulk diffusion couples, selected to explore a wide range of compositions representative of aging bondcoats, permitted to extract an elastic viscoplastic behaviour law of NiAl(Pt), both in the B2 phase and in the martensitic phase. Some mechanical properties could also be determined on NiAl(Ru) and NiAl(Zr) systems. Finally the results of a few tests performed on thermal barrier bondcoats could be correlated with the results obtained on bulk materials
6
Chien, H. H. "The mechanical properties of aluminide coatings." Thesis, Cranfield University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.352970.
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Oki, Makanjuola. "Conversion coatings on aluminium." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390302.
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Mirhashemihaghighi, Shadi. "Nanometre-thick alumina coatings deposited by ALD on metals : a comparative electrochemical and surface analysis study of corrosion properties." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066349/document.
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La protection contre la corrosion par des films ultramince (≤50 nm) d'alumine déposées par ALD sur le cuivre et l'aluminium à 250°C a été étudiée dans une solution aqueuse 0,5 M de NaCl en combinant méthodes d'analyse électrochimique et de surface. L'étude de l'alumine ALD sur un substrat Cu comprend l'effet de l'épaisseur du revêtement, l'effet de l'oxyde interfacial, l'effet de la préparation de la surface et la durabilité du revêtement. Pour le substrat Al, le travail a porté sur l'examen de l'effet de l'épaisseur du revêtement. Les revêtements ont montré d'excellentes propriétés de corrosion sur des substrats Cu électropoli, tandis qu'ils ont échoué à protéger le substrat recuit, de fait d'une mauvaise adhérence à une surface lissée. L'amélioration de la résistance à la corrosion d'alumine ALD sur le substrat Cu est obtenue en l'absence de vieillissement de l'oxyde natif interfacial, et sa modification par un prétraitement. En dépit de remarquables propriétés d'étanchéité sur un substrat Cu électropoli, la protection contre la corrosion de l'alumine ALD n'est pas durable. Le revêtement du substrat Al avec l'alumine ALD conduit à l'augmentation significative de la résistance à la corrosion. Le potentiel de piqûration est augmenté en présence des revêtements l'épaisseur de 20 et 50 nm, ce qui n'a pas été obtenus avec 10 nm en raison de sa faible épaisseur. Cette étude est une étude préliminaire pour l'application de revêtements d'alumine ALD pour la protection contre la corrosion des alliages Al-Cu en combinaison avec d'autres compositions ALDCorrosion protection by ultrathin (≤ 50 nm) alumina films deposited by atomic layer deposition (ALD) on copper and aluminium at 250°C was studied in 0.5 M NaCl aqueous solution by combining electrochemical and surface analytical methods. The study of ALD Al2O3 on Cu substrate included investigation of the effect of the coating thickness, the effect of an interfacial oxide, the effect of surface preparation and the durability of the coating. For ALD Al2O3 on Al substrate, the work focused on the examination of the effect of the deposited coating thickness. ALD alumina coatings showed excellent corrosion properties on electropolished copper substrates, while they failed to protect the annealed substrate, as a result of poor adhesion to a smoothened surface. Modification of interfacial native copper oxide by its pre-treatment led to better corrosion protection of ALD alumina on copper substrate. Despite its remarkable sealing properties on electropolished Cu substrate, corrosion protection of ALD alumina was not durable. Coating of Al substrate with ALD Al2O3 led to significant increase of polarization resistance. Better performance was obtained for 10 and 20 nm coatings on Al than on Cu. Apart from significant decrease of current, the pitting potential was increased in presence of 20 and 50 nm coatings, which was not achieved with 10 nm due to its low thickness. This study was a preliminary study for application of ALD alumina coatings for corrosion protection of Al-Cu alloys in combination with other ALD compositions
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Etheridge, Andrea Mary. "Conversion coatings on aluminium alloys." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307051.
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Rayner, Timothy James. "Development and evaluation of yttrium modified aluminide diffusion coatings." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0008/MQ34151.pdf.
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Fox, Vanessa. "The in-situ mechanical properties of modified aluminide coatings." Thesis, Cranfield University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309588.
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Long, K. "Aluminide-based coatings for turbine blade internal cooling passages." Thesis, Cranfield University, 2004. http://dspace.lib.cranfield.ac.uk/handle/1826/11002.
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The development of aero-gas turbines is moving towards more efficient engines
with higher pressure ratios and increased Turbine Entry Temperatures. This leads to
increases in overall turbine blades temperatures which has resulted in the widescale
development of turbine blades with film cooling and Thermal Barrier Coatings (TBCs)
which reduce the metal temperature of the blade. The air used for film cooling is
directed around the blade by internal passages within the blade, current engines are
experiencing hot corrosion in areas of these internal passages, even with internal
aluminide coatings. The trend for more efficient engines means that corrosion of the
internal passages will become more common, coupled with the inability to inspect the
internal passages of turbine blades in service, results in a requirement for an improved
coating for the internal passages of turbine blades.
The aim of this study was to develop a coating which provides improved
corrosion and oxidation performance over a standard vapour aluminide on single crystal
CMSX-4 turbine blades material. The coating needs to be compatible with the Rolls-
Royce bond coat and the Rolls-Royce manufacturing strategy.
The study investigated a number of additions which could be used to
improve the performance of an aluminide coating. Silicon was selected as the optimum
addition on the basis of performance and ease of deposition. The work then assessed the
influence of various production parameters on the formation of a silicon-aluminide
coating. It was possible to control the level of silicon deposited in the coating.
Performance testing, using cyclic oxidation and salt recoat hot corrosion
tests, of various silicon aluminides developed in this programme demonstrated at least a
doubling in life compared with vapour aluminide coatings.
13
George, Faith Olajumoke. "Chromium-free conversion coating of aluminium-copper alloys." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/chromiumfree-conversion-coating-of-aluminiumcopper-alloys(5176c8af-02af-44a8-a47f-44b5a0c2585c).html.
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Aluminium alloys are frequently pre-treated by a conversion coating before application of an organic coating in order to improve the corrosion resistance and adhesive properties of the surface and the corrosion resistance provided by the system. Chromate-containing conversion coatings are commonly used for this purpose. However, legislation limits future use of hexavalent chromium compounds due to their toxic and carcinogenic nature. Therefore, alternative, so-called chromium-free conversion coatings are being developed that are more environmentally-compliant.The purpose of the present work has therefore been to contribute to a better understanding of how the aluminium substrate affects the formation and properties of conversion coatings for adhesive bonding. In particular, a chrome-free zirconium-based conversion treatment process has been investigated as a possible replacement for conventional chromate conversion treatment. The influence of the conversion time on the thickness of the formed layer on pure aluminium was investigated using complementary surface analytical techniques. The conversion time was varied between 30 and 600 seconds.In this study, the structure and composition of zirconium-based chromium-free conversion coatings on magnetron sputtered superpure aluminium and a range of aluminium-copper alloys were characterised as a function of immersion time in the aqueous conversion bath to understand the mechanism of coating formation and protection. However, the presence of copper significantly influences the coating development and ultimately the performance of the conversion coatings formed on binary copper-containing aluminium alloys.The morphology and composition of the coatings have been probed using transmission electron microscopy, Rutherford backscattering spectroscopy and glow discharge optical emission spectroscopy, with loss of substrate through growth of the conversion coating also quantified. A comparison of the RBS spectra obtained for the superpure aluminium specimens after different immersion times revealed that zirconium (Zr) and oxygen (O) peaks were wider for longer immersion times, indicating thickening of the coating with increased immersion times. Thus, increasing the immersion time resulted in an increase in coating thickness but little change in coating composition occurred as determined by the RBS RUMP simulations. Alloying decreases the coating thickness, as well as metal consumption. Here, aspects of the corrosion behaviour of superpure aluminium and aluminium-copper alloys were also considered using electronoptical, electrochemical and surface analytical probing. The influence that short and prolonged treatment times exert on the performances of such conversion coating is discussed. The conversion coating formed after 60 s and 180 s of immersion in the zirconium-based conversion coating bath provide good corrosion resistance which can be attributed to the high stability of the compounds that constitute the surface oxide layer, and good adhesion properties.
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Rodahl, Silje. "Adhesian of organic coatings on aluminium." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-5410.
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Cardilli, Emanuele. "Aluminium-based coatings for cadmium replacement." Thesis, Cranfield University, 2008. http://dspace.lib.cranfield.ac.uk/handle/1826/3208.
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Cadmium electroplating is widely used in the aerospace industry for the corrosion protection of high strength steels. Cadmium is also used as compatible coating to reduce the galvanic corrosion generated in the assembly of components manufactured with different materials. However, environmental and safety concerns over the high toxicity of cadmium has led to the investigation of suitable replacements. Aluminium coatings are promising coatings for the replacement of electroplated cadmium. Previous studies have shown that the use of SermeTel 984, a commercial aluminium sprayed coating, is beneficial in eliminating the hydrogen direct embrittlement without increasing the risk of re-embrittlement. However, the coating has shown to be prone to passivation in the mild corrosive environment. The addition of active zinc and magnesium particles are thought to avoid the passivation of the aluminium. A range of modified SermeTel 984 coatings, containing 0.5%, 3%, 10% and 50% of zinc, and SermeTel 984 modified with the addition of 30% and 50% of Mg/Al alloy particles in weight have been evaluated as possible alternatives. Chromium free SermeTel 984 and a SermeTel 984 modified with aluminium alloy 7075 particles together with IVD aluminium coatings have also been included in the project. The sacrificial protection of the new coatings has been evaluated together with the associated risk of hydrogen re-embrittlement and compared with the electroplated cadmium. Zinc modified SermeTel 984, containing 1% of zinc and 5% of zinc electroplated aluminium, IVD aluminium and electroplated Zn-Ni coatings have been studied as alternative coatings to cadmium as compatible coatings. Slow strain rate testing has been performed to study the effect of hydrogen on the re- embrittlement of steel substrate as a result of the corrosion of the aluminium-based coatings in 3.5% NaCl. Linear polarisation testing in 3.5% NaCl has been used to evaluate the self-corrosion rates of the coatings; galvanic coupling measurements have been used in the case of steel substrate to evaluate the sacrificial properties or, in the case of bronze/aluminium assembly, to evaluate the compatibility properties of the coatings. Polarisation behaviour tests have been used to study the anodic or cathodic control of the corrosion mechanisms. Total corrosion, calculated as the addition of self-corrosion and galvanic corrosion, has been calculated to evaluate the duration of the coating in service compared to electroplated cadmium.
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Burgmann, Flame Astra, and f. burgmann@usyd edu au. "Nanostructured Multilayer Coatings of Aluminium and Aluminium Oxide with Tungsten." RMIT University. Applied Sciences, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080424.135857.
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The development of nanostructured coatings which exhibit enhanced mechanical properties is currently of interest due to the importance of high performance coatings in a large range of applications. Single layer coatings have predominantly been used for these demanding applications, however the promising mechanical properties observed in multilayer coatings has shifted the focus of current research. In particular, there has been reports of the use of alternating materials with opposing mechanical properties, as seen in the abalone shell, which have exhibited hardness and toughness values significantly greater than either of their constituent materials. The main objective of this thesis was to fabricate Al/W nanostructured multilayers and determine if they exhibit enhanced mechanical properties. The Al/W nanostructured multilayers were fabricated using two different deposition techniques: pulsed magnetron sputtering and cathodic arc deposition. These two techniques differ in the energy of the depositing species and this results in significant differences in film properties. The indentation hardness of the coatings was measured using a Hysitron Nanoindenter. The relationship between the mechanical properties and microstructure was obtained using a range of characterisation techniques. Auger electron spectroscopy (AES), energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS) were used to determine the chemical composition and stoichiometry, while cross-sectional transmission electron microscopy (XTEM) and energy filtered transmission electron microscopy (EFTEM) were used to explore the microstructure. The findings of this thesis showed very different results for the two deposition techniques. Although sputtering successfully produced well defined multilayers, no evidence of enhanced hardness was found for periods between 5 and 200 nm. On the other hand, arc deposited samples with intended periods between 1 and 200 nm showed a hardness enhancement above that of pure W, however the samples of highest hardness did not contain Al layers for much of their thickness. Arc deposited samples with the finest nominal periods (1 and 2 nm) contained W-Al intermetallics and were soft. The hardening mechanism was not attributed to a multilayer structure, rather to the introduction of defects in the W layers which acted as pinning sites for dislocations. A modified Hall-Petch equation for hardness enhancement fitted the data for W films prepared by pulsed cathodic arc in which the grain diameter was replaced by the nominal multilayer period. The difficulty producing Al layers on W surfaces in the cathodic arc was overcom e by changing the film growth mechanism by introducing Ar or O2 at the W/Al interface. In the latter case, Al2O3/W multilayers were formed but again showed no hardness enhancements. Complete microanalysis and characterisation of the multilayer structures is vital in determining the mechanisms which govern the hardness enhancements. The evidence in this thesis suggests that the defect density, and not the presence of interfaces are responsible for the hardness enhancement effect.
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Busso, Esteban Pedro. "Cyclic deformation of monocrystalline nickel aluminide and high temperature coatings." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/13973.
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Xiao, Xiaoling, and S3060677@student rmit edu au. "Characterization of nano-structured coatings containing aluminium, aluminium-nitride and carbon." RMIT University. Applied Sciences, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20081217.100453.
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There is an every increasing need to develop more durable and higher performing coatings for use in a range of products including tools, devices and bio-implants. Nano-structured coatings either in the form of a nanocomposite or a multilayer is of considerable interest since they often exhibit outstanding properties. The objective of this thesis was to use advanced plasma synthesis methods to produce novel nano-structured coatings with enhanced properties. Coatings consisting of combinations of aluminum (Al), aluminum nitride (AlN) and amorphous carbon (a-C) were investigated. Cathodic vacuum arc deposition and unbalanced magnetron sputtering were used to prepare the coatings. By varying the deposition conditions such as substrate bias and temperature, coatings with a variety of microstructures were formed. A comprehensive range of analytical methods have been employed to investigate the stoichiometry and microstructure of the coatings. These include Transmission Electron Microscopy (TEM), Scanning Transmission Electron Microscopy (STEM), Electron Energy Loss Spectroscopy, Auger Electron Spectroscopy, X-ray diffraction and Raman spectroscopy. In addition to the investigation of microstructure, the physical properties of the coatings were measured. Residual stress has been recognized as an important property in the study of thin film coatings since it can greatly affect the quality of the coatings. For this reason, residual stress has been extensively studied here. Hardness measurements were performed using a nano indentation system, which is sensitive to the mechanical properties of thin films. This thesis undertook the most comprehensive investigation of the Al/AlN multilayer system. A major finding was the identification of the conditions under which layers or nanocomposite form in this system. A model was developed based on energetics and diffusion limited aggregation that is consistent with the experimental data. Multilayers of a-C and Al were also found to form nanocomposites. No hardness enhancement as a function of layer thickness or feature size was observed in either the Al/AlN or a-C/a-C systems. It was found that the most important factor which determines hardness is the intrinsic stress, with films of high compressive stress exhibiting the highest hardness. Nano-structured multilayers of alternating high and low density a-C were investigated. For a-C multilayers prepared using two levels of DC bias, evidence of ion beam induced damage was observed at the interfaces of both the low and high density layers. In addition, the structure of the high density (ta-C, known as tetrahedral amorphous carbon) layers was found to be largely unchanged by annealing. These results extend our understanding of how a-C form from energetic ion beams and confirms the thermal stability of ta-C in a multilayer. This thesis also presented the first attempt to synthesis a-C multilayered films with a continuously varying DC bias in sinusoidal pattern. The resulting films were shown to have a structurally graded interface between layers and verified that ion energy and stress are the most important factors which determine the structure of a-C films.
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Tyurin, Yu, O. Ivanov, O. Kolisnichenko, M. Kovaleva, I. Duda, O. Maradudina, and Y. Trusova. "Properties of nanostructured composite titanium coating on aluminium surface." Thesis, Видавництво СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20488.
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Xu, Nan Materials Science & Engineering Faculty of Science UNSW. "Corrosion behaviour of aluminised steel and conventional alloys in simulated aluminium smelting cell environments." Awarded by:University of New South Wales. School of Materials Science & Engineering, 2002. http://handle.unsw.edu.au/1959.4/18760.
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Aluminium smelting is a high temperature electrometallurgical process, which suffers considerable inefficiencies in power utilization and equipment maintenance. Aluminium smelting cell works in the extreme environments that contain extraordinarily aggressive gases, such as HF, CO and SO2. Mild steel used as a structural material in the aluminium industry, can be catastrophically corroded or oxidized in these conditions. This project was mainly concerned with extending the lifetime of metal structures installed immediately above the aluminium smelting cells. An aluminium-rich coating was developed on low carbon steel A06 using pack cementation technique. Yttria (Y2O3) was also used to improve the corrosion resistance of coating. Kinetics of the coating formation were studied. XRD, FESEM and FIB were employed to investigate the phase constitution and the surface morphology. Together with other potentially competitive materials, aluminium-rich coating was evaluated in simulated plant environments. Results from the long time (up to 2500h) isothermal oxidation of materials at high temperature (800??C) in air showed that the oxidation resistance of coated A06 is close to that of stainless steel 304 and even better than SS304 in cyclic oxidation tests. Coated A06 was also found to have the best sulfidation resistance among the materials tested in the gas mixture contains SO2 at 800??C. Related kinetics and mechanisms were also studied. The superior corrosion resistance of the coated A06 is attributed to the slow growing alpha-Al2O3 formed. Low temperature corrosion tests were undertaken in the gas mixtures containing air, H2O, HCl and SO2 at 400??C. Together with SS304 and 253MA, coated A06 showed excellent corrosion resistance in all the conditions. The ranking of the top three materials for corrosion resistance is: 253MA, coated A06 and SS304. It is believed that aluminised A06 is an ideal and economical replacement material in the severe corrosive aluminium smelting cell environment.
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Dent, A. H. "The microstructure of diffusion aluminide coatings on a Ni based alloy." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598506.
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The microstructures of both aluminide and platinum alumidide diffusion coatings on a single crystal Ni-based superalloy have been characterised in the 'as received' as well as the degraded state. X-Ray diffraction and a wide range of transmission electron microscopy (TEM) techniques including quantitative thin window EDX analysis have been used to examine the different coatings. A martensitic transformation from the β-phase of the coating which occurs as a result of a loss of aluminium during its degradation was examined in depth. This transformation from the B2 structure to a twinned form of the L10 structure was compared to a similar and related transformation which is known to occur for the binary β-NiA1 phase on cooling. A number of interesting differences between the two transformations are presented. Model alloys with a range of compositions, determined from using quantitative TEM EDX analysis of the martensite phase of the degraded coatings, were mechanically deformed both at room temperature and at 600°C. The test data and resultant microstructures have been used to suggest a possible reason for the ability of the diffusion coatings to reduce spalling of the surface oxide in service by the relaxation of stresses formed between the substrate, coat and surface scale.
22
Pan, Deng. "Mechanical properties of diffusion aluminide bond coats for thermal barrier coatings." Available to US Hopkins community, 2003. http://wwwlib.umi.com/dissertations/dlnow/3080741.
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De, Silva Eugene. "Intensified plasma assisted processing : a novel process in surface coating technology." Thesis, Manchester Metropolitan University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366231.
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Frigaard, Ian Alistair. "Mathematical modelling of an aluminium spray process." Thesis, University of Oxford, 1993. http://ora.ox.ac.uk/objects/uuid:6fb9d792-4848-4d2c-8f32-c8b6041f3e06.
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Spray-forming is a newly developed industrial metal forming process in which a cylindrical metal billet is produced by the incremental deposition and solidification of an atomised metal spray on a moving substrate. A mathematical model is developed to describe billet growth and heat flow within spray-formed aluminium alloy billets. In the first part of the thesis, growth dynamics of the billet are considered. Conservation of mass at the billet surface yields a single first order quasi-linear partial differential equation for the movement of the billet surface; the nonlinearity arising from the possibility of surface shadowing. The existence of two distinctly different timescales, amongst the process motions governing billet growth, prompts the use of an averaging method. The resulting averaged equations permit analysis and are shown to provide a valid asymptotic approximation to the billet surface motion on the timescale 1/∊, for a suitably defined class of billet surfaces. The parameter ∊ ≪ 1 is the ratio of the two process timescales. Conditions under which the crown profile of the cylindrical billet becomes steady are analysed, through the averaged equations, and the stability of such profiles is examined. Computed examples of single and multiple steady state crown profiles are given. The averaged equations are also solved numerically to provide a model for transient billet growth on a "slow" timescale; results are presented. The second part of the thesis considers heat flow within the growing billet. Phase change is incorporated using an enthalpy formulation of the energy equation. The resulting equation is a nonlinear heat equation that must be solved in an expanding domain, the boundary of which is determined by solution of the billet growth model equations. Conduction on the billet length-scale takes place only on the slow timescale, with more rapid heat flow taking place only close to the billet surface. Accordingly, billet heat flow is analysed through the assumption that there is a thermal boundary layer close to the billet surface, which is driven by the "rapid" timescale spray deposition, with heat flow in the remainder of the billet driven by the time-averaged growth. The boundary layer equation is a one dimensional nonlinear advection-diffusion equation, with a nonlinear boundary condition that incorporates the intermittent deposition from the spray in the form of an irregular pulse. This equation is solved numerically using an implicit finite difference method. The slow-time heat flow is two dimensional, (assuming axisymmetric slow-time billet growth), and must also be solved numerically. For this an implicit predictor-corrector method is used. The predictor stage uses a "splitting" method, adapted from the fully implicit L.O.D. method to take account of the expanding domain. The method appears to be stable and consistent. Various numerical results are presented. The model provides significant new understanding of the dynamics of billet growth and succeeds in providing a useful framework within which the transient heat flow that occurs during spray deposition, on a number of different timescales and length-scales, can be understood. Comparison of computed model predictions with real sprayed billets confirms the validity of the model. The thesis is concluded with a summary of results and a look at possible future directions for research in this area.
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Feng, Zuwei. "Formation of sol-gel coatings on aluminium alloys." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/formation-of-solgel-coatings-on-aluminium-alloys(7e6eed7e-959b-487d-bc3a-5950d584ca42).html.
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Organically modified sol-gel coatings have been investigated as potential replacements for chromate conversion coating of AA1050 and AA2024 aluminium alloys. The coatings were prepared by a combination of a completely hydrolysable precursor of tetra-n-propoxyzirconium (TPOZ), with a partially hydrolysable precursor of glycidoxypropyltrimethoxysilane (GPTMS). GPTMS contains organic functional groups, which are retained in the sol-gel coatings after the hydrolysis-condensation process. Different process parameters, e.g. GPTMS/TPOZ ratios, withdrawal speeds, solvent water concentrations, and curing temperatures were studied. Coatings produced using a low GPTMS/TPOZ ratio and a high withdrawal speed generated significant cracks due to the shrinkage of the coatings. It was found that increase of organic moieties reduced the shrinkage of the coatings and the tendency for crack formation. By controlling process parameters and ratios of organic and inorganic moieties, crack-free sol-gel coatings from 0.1 μm to 9 μm thick can be achieved. The sol-gel coatings formed are amorphous and contain organic epoxy-ether retained silicon oxide, silicon hydroxide, zirconium oxide, zirconium hydroxide, and zirconium acetate. The Si/Zr ratios of resultant sol-gel coatings are proportional to the initial GPTMS/TPOZ ratio. Cerium oxide nanoparticles were successfully incorporated into sol-gel coatings with a single layer and double layer sol-gel process. Through the dip coating process, crack-free sol-gel coatings, of varied thickness, were developed on different aluminium substrate, including electropolished superpure aluminium, magnetron sputtered aluminium with varied copper contents from 0 to 30 wt.%, and commercial AA1050 and 2024 aluminium alloys. Sol-gel coatings formed on commercial AA1050 and 2024 aluminium alloys revealed a significant passivation in 3.5 wt.% sodium chloride solution during anodic polarisation when the sol-gel coating is more than 1 µm thick and proper surface pretreatments of the alloys were used. Corrosion tests by immersion in 3.5 wt% sodium chloride solution and by salt spray in 5 wt.% sodium chloride solution revealed that sol-gel coatings successfully protected AA2024 aluminium alloy against the aggressive environment and have the potential to replace chromate containing coating systems.
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Chalaftris, George. "Evaluation of aluminium-based coatings for cadmium replacement." Thesis, Cranfield University, 2003. http://dspace.lib.cranfield.ac.uk/handle/1826/103.
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Cadmium electroplating is widely used in the aerospace industry for the corrosion protection of aircraft components like fasteners manufactured from non corrosion resisting high strength steels. However, environmental and safety concerns over the high toxicity of cadmium and its compounds have led to the investigation of suitable replacements. Alternatives to cadmium should offer effective corrosion protection and have no detrimental effects on the steel substrate. Hydrogen is known to be absorbed during processes like electroplating, thus causing hydrogen embrittlement on high strength steel fasteners. Another source of hydrogen is the water reduction occuring in parallel with the corrosion of the coating, and thus causing re–embrittlement of the steel substrate. This study has investigated the effect of the application of two aluminium–based coatings, SermeTel CR984–LT and Galvano–Aluminium Alcotec, on the hydrogen re–embrittlement of high strength steels used for aerospace applications. Slow strain rate testing has been performed to study the effect of hydrogen on the re–embrittlement of the steel substrate as a result of the corrosion of the aluminium–based coatings in a variety of environments, such as NaCl solution, salt spray and marine atmosphere. Permeation measurements have been used to measure hydrogen uptake by unplated steel membranes potentiostatically charged at the potentials of the aluminium–based coatings, so as to simulate the amount of absorbed hydrogen due to their corrosion. Corrosion tests have been utilised to evaluate the performance of SermeTel CR984–LT and Galvano–Aluminium Alcotec.
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Ruiz, Garzon Angela Maria. "Interactions of environmentally friendly conversion coatings with aluminium." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680054.
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Mazraeh, Mohsen. "The resistance of flare stack coatings to corrosion." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251829.
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Encinas-Oropesa, Adriana. "Study of hot corrosion of single crystal superalloys and platinum-aluminide coatings." Thesis, Cranfield University, 2005. http://dspace.lib.cranfield.ac.uk/handle/1826/4519.
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At the present time, combined cycle systems for power generation (e. g. IGCC), offer increased efficiency of power generation and lower environmental emissions, specifically C02, SOx, and NOx, as well as being adaptable to most fossil fuels. Economic factors, such as the cost of the materials must be considered. Materials influence the service lifetime in the required operational environment. Solid fuels like coal and biomass produce different combustion environments containing a range of contaminants that, when they reach their melting points, may cause accelerated corrosion, affecting directly the service life time of the gas turbine constructional materials. This accelerated corrosion is known as Hot Corrosion. The aim of this study was to develop, an understanding of the influence of these environmental factors on rate of hot corrosion of modem turbine materials, i. e. the single crystal alloys CMSX4 the SC2 , both uncoated and PtAl coated that are needed for a gas turbine blade and vanes operating in a range of hot corrosion environments expected in an lGCC plant. To achieve this aim, a series of laboratory corrosion tests was planned to simulate the same corrosion environment as in industrial high temperature gas turbine operation. Following established procedures for corrosion testing, samples were exposed in a controlled atmosphere furnace to a mix of gases (air/SO241CI) with a cyclic exposure time of 50 and/or 100h duration. Each cycle, samples were removed to be recoated with an alkali salt mixture to a total exposure time of 500h and or 1000h. Cross sections were examined by SEM/EDX to identify the mode of hot corrosion attack. To quantify the rate of corrosion, samples were measured pre-exposure and post-exposure, and this corrosion data was statistically assessed. Finally, from this quantitative data, life prediction models were developed to describe/predict the onset of hot corrosion and the corrosion rates observed under different gas compositions, and various deposition fluxes, both at typical type I and type II hot corrosion temperatures in terms of incubation and propagation periods. Separate models have been developed for the two single crystals superalloys: CMSX4 and SC2, in both the uncoated and platinum aluminide coated condition. The goodness of fit as defined by the regression coefficient varies from 0.88 to 0.99 for the propagation models at 700 and 900°C. The incubation models are as precise at 7001C but less precise at 9001C with regression coefficients of 0.78-0.94. I
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Fasuba, Omoniyi. "Electrochemical corrosion evaluation of aluminium-based coating alternatives to cadmium plating." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/6730/.
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Electroplated cadmium has been employed for decades as a coating material to provide protection for steels against corrosion because of its combination of inherent corrosion resistance in atmospheric conditions, bi-metallic corrosion characteristics, lubricity and good electrical conductivity. However, it is a toxic metal and known carcinogenic agent, which is plated from an aqueous bath containing cyanide salts. For these reasons, the use of cadmium has been banned in Europe for most industrial applications. Nevertheless, the aerospace industry is still exempt due to stringent technical and safety requirements associated with aeronautical applications, until a reliable and acceptable replacement is found. Aluminium-based coatings are potential candidates to replace cadmium because of their low toxicity and high corrosion resistance in aggressive media. The corrosion properties of commercially available aluminium-based coatings: Al-Zn flake inorganic spin, Al-based slurry sprayed and arc sprayed Al coatings deposited on mild steel were investigated. Al, AlCr and AlCr(N) coatings deposited by Electron Beam Physical Vapour Deposition (EBPVD) technique on M2 and 17/4 PH steel substrates at 3000 C were also investigated. The range of electrochemical techniques used to evaluate the corrosion properties of the coatings include: Open-circuit Potential (OCP), Potentiodynamic Polarisation (PDP), Electrochemical Impedance Spectroscopy (EIS), Galvanic coupling and Electrochemical Noise (ECN) measurements. The structure and composition of the coatings were characterised by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) spectroscopy. For the commercially available Al-based coatings, the Al-based slurry coating exhibited an open-circuit potential closer to the mild steel substrate than other coatings, as well as a low corrosion current density and a more positive corrosion potential. In terms of galvanic compatibility with the steel substrate, both the Al-Zn flake inorganic spin coating and the Al-based slurry sprayed coating show low galvanic current, in comparison with the arc sprayed Al coating and cadmium. This behaviour confirms their superior cathodic protection capability and galvanic compatibility over other coatings. Good correlation between data from the ECN, OCP, potentiodynamic polarisation and EIS measurements was found; in particular electrochemical noise resistance (Rn) correlates well with polarisation resistance (RP) and corrosion current density (icorr). However, magnitudes of elements in EIS results vary widely when compared to those of the potentiodynamic polarisation tests. Furthermore, analysis of the current-potential noise time data reveals uniform corrosion for cadmium and Al-Zn flake inorganic coating, passivation for Al-based slurry sprayed coating and localised corrosion for arc sprayed Al coating. However, the polarisation results revealed localised corrosion for Al-Zn flake inorganic coating, indicating that the corrosion mechanism of the coating is mixed (i.e. both localised and uniform). For the EBPVD Al-based coatings, OCP and PDP measurements show that the incorporation of chromium and nitrogen in the coatings enhanced the corrosion resistance. However, this also resulted in the ennoblement of the corrosion potential, hence the AlCr and AlCr(N) PVD coatings deposited on M2 steel could not preserve their sacrificial character, while the same coatings deposited on 17/4 PH steel remained sacrificial with respect to the substrate. This difference is due to the respective open-circuit potential of the two substrates. Good agreement between data from the different electrochemical techniques was found. The AlCr(N) coatings show strong passivation, the AlCr coating deposited on M2 steel displayed localised form of corrosion, while its counterpart deposited on 17/4 PH corroded uniformly. This discrepancy lies in the difference in their coating morphology and Cr content. Thus, the corrosion behaviour of the EBPVD Al-coatings deposited on M2 steel is strongly dependent on the chromium and nitrogen content. Overall, the AlCr coating deposited on the 17/4 PH steel demonstrates combined barrier and sacrificial protection capacity. Characteristic charge, q and frequency of corrosion events, fn could not distinguish properly between the different types of corrosion associated with the EBPVD Al-based coatings, indicating that these parameters cannot be relied upon as true indicators of corrosion mechanisms. Finally, it was shown that utilising the localisation index (LI) and the roll-off slope of power spectra density (PSD) to discriminate between different types of corrosion needs further investigation, especially with regards to passive systems, where ECN measurements are often contaminated with extraneous noise sources, leading to false estimates of values obtained from these parameters.
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Persson, Björn, and johanna Svensk. "Corrosion protection of powder coatings : Testing the barrier properties and adhesion of powder coating on aluminum for predicting corrosion protection by Electrochemical Impedance Spectroscopy." Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Produktutveckling, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-36772.
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The choice of corrosion protection system depends on the environment and needed lifetime for the product. The right corrosion protection should be selected in a sustainable point of view, since a well-selected coating system can reduce the environmental and economical impact, by using less and better material. The systems used for classifying corrosion protection often give a passed/not passed result for the number of years it is expected to last in a specific corrosive environment. In the last decades, Electrochemical Impedance Spectroscopy (EIS) has become a popular method for evaluating corrosion protection for organic coatings. EIS can collect quantitative data by monitoring the coatings electrochemical behavior over time, which can be used for optimizing the coating system. The purpose of this thesis was to try to predict how different combinations of coating layers and substrates will perform as a corrosion protection, which could provide information that can optimize the coating process. In this thesis, EIS has been used as a test method to evaluate organic coating systems for corrosion protection, by looking at barrier properties and adhesion for powder coatings on aluminum substrates. The main part of the coatings were applied in the coating plant at Fagerhult AB, but an external supplier has been used as a reference. The powders used in the coating process were based on polyester resins and the substrates were different aluminum alloys. The EIS measurements were performed in the chemistry lab at the School of Engineering at Jönköping University and depending on the sample setup was each sample evaluated for two or four weeks of testing. Two groups of samples had intact coatings and a third group had samples with an applied defect in the coating. The analysis of sample setups with intact coatings showed that the topcoat absorbed water faster than the primer. The samples showed no significant degradation in corrosion protection for the evaluated period and could thereby not provide enough information to be able to conclude which setup give the best corrosion protection over time. The samples with a defect in the coating indicated that two of the substrates provided similar adhesion in the coating-substrate interface. The coating from the external supplier was also included in the test and it showed the best adhesion of the tested samples. The main conclusion is that the coating system used at Fagerhult AB provides a very good corrosion protection. Longer testing time with EIS measurements on intact coatings is needed to be able to rank the different sample setups by failure of corrosion protection.
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Capuzzi, Stefano. "Optimization of the aluminium refining process." Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3422890.
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High quality scrap is the dream of all the smelters but it is expensive. Therefore low quality scrap has also to be re-melted. Here two strategies have to be taken into account:
increasing the scrap quality inside the refinery and removing the non-metal content during the re-melting of the scrap
The aim of this doctoral thesis is to support the aluminium recycling industry in both these aspects highlighting the influence of the pre-melting scrap treatments and the melting practices on the effectiveness of the recycling process in terms of metal recovery.I rottami di alta qualità sono i più facile da riciclare, ma anche i più costosi. Due vie sono percorribili per rendere possibile il riciclo di rottami con un alto livello di elementi non desiderati: aumentarne la qualità attraverso appositi trattamenti pre-fusione e rimuovere il contenuto non metallico durante la rifusione Scopo di questa tesi di dottorato è quello di sostenere l'industria del riciclaggio dell'alluminio in entrambi questi aspetti, evidenziando l'influenza dei trattamenti pre-fusione del rottame e delle pratiche di fusione sull'efficacia del processo di riciclaggio in termini di resa metallica del processo stesso.
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Abdul-Mahdi, F. S. "Tribological characteristics of coatings on aluminium and its alloys." Thesis, Brunel University, 1987. http://bura.brunel.ac.uk/handle/2438/5016.
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Hard anodising on aluminium and its alloys has been widely practised for many years in order to improve the resistance of the otherwise poor wear characteristics of aluminium. In recent years there has been an increasing interest in other treatments and coatings, on both aluminium and other base metals. The aim of this investigation is to explain the tribological performance and wear mechanism(s) of an uncoated aluminium alloy, four anodic coated alloys, and also an electroless nickel alloy. All of the coatings are produced on three different aluminium alloys. The thickness of the anodic films is 30-35 micron, as this thickness falls within the range commonly used by industry. In an endeavour to explain the role of coating thickness on wear life, electroless nickel alloy has been produced in a range of thicknesses of 10, 20 and 30 micron. To evaluate abrasive and adhesive wear, the samples were rubbed against a single point diamond and steel ball, respectively, in a reciprocating movement at room temperature and 65-75% relative humidity, under a wide range of load and sliding distance. Some tests continued to run until a breakdown of the coatings occurred, whilst other tests were interrupted at intermediate stages. This enabled the initiation and propagation of failure mechanisms to be studied. Abrasive wear was performed under dry conditions, whereas, adhesive wear was evaluated under both dry and lubricated conditions. Wear of these coatings was proportional to the applied load and sliding distance, but there was no direct relationship between wear and hardness. The tribological performance of these coatings appears to be dictated by a) the composition of the substrate, b) the chemical and physical nature of the coatings and c) the test conditions. Under boundary lubricated conditions there was a considerable increase in the wear life of the coatings. A three dimensional surface texture is superior to a machined surface, in controlling contact conditions. There is an approximate linear relationship between coating thickness and wear life for electroless nickel alloys. These coatings predominantly fail by adhesion, plastic deformation and brittle fracture. A microscopic model for fracture of brittle materials, under both static and dynamic conditions for abrasive and adhesive wear correlates very well with the behaviour of these coatings. Analytical interpretation of adhesive wear was made by separately calculating the coefficient of wear "K" of the counterbodies. This information enables an improved understanding of the wear test itself to be added to the model of the wear mechanisms involved.
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Smit, Mascha. "Titanium-based no-rinse conversion coatings on aluminium alloys." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301402.
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Danilidis, Ioannis. "Manganese-based no-rinse conversion coatings for aluminium alloys." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299758.
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Rebholz, Claus. "Synthesis and properties of titanium aluminium boron nitride coatings." Thesis, University of Hull, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310329.
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Amiriyan, Mahdi. "Development of ceramic reinforced iron aluminide based composite coatings for wear resistant applications." Doctoral thesis, Université Laval, 2019. http://hdl.handle.net/20.500.11794/35012.
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Les composés intermétalliques Fe₃Al et leurs revêtements composites sont des matériaux structuraux potentiels pour des applications tribologiques. Parmi les composites, ceux obtenus par broyage mécanique à haute énergie possèdent plusieurs avantages, en particulier une fabrication rentable. Le broyage à billes à haute énergie permet également une large gamme de fraction volumique des particules de renforcement. Dans cette recherche, Nous avons préparé des revêtements composites à matrice d'aluminiure de fer, basés sur la composition chimique de Fe₃Al avec des particules de renforcement de TiC et de TiB₂ en utilisant un broyeur à billes à haute énergie et déposé par la technique HVOF (High Velocity Oxy Fuel). L'effet des paramètres de traitement tels que la durée du broyage et le traitement thermique subséquent sur les la matière première destinés à la projection par HVOF a été étudié. Les paramètres de traitement ont joué des rôles importants sur la poudre composite et par la suite sur la microstructure, les propriétés mécaniques et tribologiques des revêtements. Le but de la première phase expérimentale de ce travail était d'étudier l'effet des particules de TiC in situ sur la microstructure, le comportement mécanique et tribologique des revêtements de Fe₃Al déposés par HVOF. Dans cette étape, des poudres composites Fe₃Al / TiC avec différentes quantités de carbure de titane ont été produites par broyage à haute énergie. Un mélange de Fe₃Al-Ti-C a été broyé pendant 6 h suivi d'un traitement thermique à 1000 °C pendant 2 h sous vide poussé. Des revêtements composites d'aluminure de fer renforcés au TiC in situ ont été préparés pour améliorer la dureté Vickers et la résistance à l'usure des intermétalliques de Fe₃Al. Les revêtements composites consistent principalement en une phase de TiC uniformément dispersée dans des lamelles de la matrice de Fe₃Al. Les revêtements composites ont montré une dureté Vickers croissante avec l’augmentation de la quantité de TiC, allant jusqu'à 70 % en moles de TiC. La résistance à l'usure par glissement à sec des revêtements a été augmentée avec l'addition de particules de TiC formées in situ. Les revêtements composites de Fe₃Al déposés par HVOF avec des renforts en TiC de 50 % et 70 % en moles présentaient une excellente résistance à l'usure par glissement. Le mécanisme d'usure dominant de ces revêtements était l'abrasion et l'oxydation. Dans une autre étape de ce travail, des poudres composites de Fe₃Al-TiB₂ avec deux quantités différentes de borure ont été produites par le dépôt par high Velocity Oxy Fuel (HVOF) sur un substrat en acier. Les revêtements composites consistaient principalement en une phase de TiB₂ pré-synthétisée et uniformément dispersée dans des lamelles de la matrice de Fe₃Al. Il a été montré qu'en augmentant la fraction volumique du TiB₂, la dureté Vickers et la résistance à l'usure par glissement des revêtements contre le contre-corps en alumine (6,33 mm de diamètre) étaient augmentées. L'augmentation de la résistance à l'usure était censée être liée à l'amélioration de la dureté, qui à son tour est due à la présence de particules de TiB₂ dans la matrice Fe₃Al. Le taux d'usure de glissement des revêtements a augmenté pour atteindre un maximum lorsque la vitesse de glissement augmente, puis il a diminué avec l'augmentation supplémentaire de la vitesse de glissement. Les analyses chimiques des surfaces usées ont montré que des vitesses de glissement plus élevées entraînent une oxydation plus élevée de la surface, probablement en raison de la température locale plus élevée. Une telle couche d'oxyde semble agir comme une barrière entre deux corps coulissants, diminuant ainsi le taux d'usure.Fe₃Al intermetallic compounds and their composite coatings are potential structural materials for tribological applications. High-energy ball milled powders possess several advantages, especially cost-effective fabrication and lower cost of reinforcement. High-energy ball mill also allows for a wide range of reinforcement volume fraction. In this research, Iron Aluminide matrix composite coatings based on Fe₃Al chemical composition with TiC and TiB₂ particles were prepared using a high-energy ball mill and deposited via the High Velocity Oxy Fuel (HVOF) technique. The effect of processing parameters such as ball milling duration and subsequent heat treatment soaking time and temperature on the phases of products as a feed stock for the HVOF gun was studied. The processing parameters played important roles on the microstructure, mechanical and tribological properties of the coatings. The aim of the first experimental stage of this work was to study the effect of in-situ TiC particles on microstructure, mechanical and tribological behavior of HVOF deposited Fe₃Al coatings. In this stage Fe₃Al/TiC composite powders with different carbide quantities were produced via high-energy ball milling of Fe₃Al-Ti-C system for 6 h followed by heat treatment at 1000 °C for 2 h under high vacuum. In-situ TiC-reinforced iron aluminide composite coatings were prepared to improve the Vickers hardness and wear resistance of Fe₃Al intermetallics. The composite coatings mainly consist of a TiC phase uniformly dispersed within lamellae of the Fe₃Al matrix. The composite coatings showed increasing Vickers hardness with increasing TiC content up to 70 mol% TiC. The dry sliding wear resistance of coatings was increased with the addition of in-situ formed TiC particles. HVOF deposited Fe₃Al composite coatings with 50 and 70 mol% TiC reinforcements exhibited excellent sliding wear resistance. The dominant wear mechanism in those coatings was abrasion and oxidation. In another stage of this work Fe₃Al-TiB2 composite powders with two different boride quantities were produced by the high Velocity Oxy Fuel (HVOF) spray deposition on a steel substrate. The composite coatings mainly consisted of a TiB₂ phase uniformly dispersed within lamellae of the Fe₃Al matrix. It was shown that by increasing the volume fraction of TiB₂ both the Vickers hardness and sliding wear resistance of the coatings against alumina counterbody (6.33 mm in diameter) were increased. The increase of wear resistance was believed to be related to the hardness enhancement, which, in turn, is due to the presence of TiB₂ particles within the Fe3Al matrix. The sliding wear rate of the coatings increased to reach a maximum as the sliding speed increases, and then it decreased with further increase of the sliding speed. The chemical analyses of the worn surfaces showed that higher sliding speeds result in higher oxidation of the surface, most likely due to the higher local temperature. Such an oxide layer seems to act as a barrier between two sliding bodies, thus decreasing the wear rate.
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Czok, Gregor Sebastian. "Particle coating by chemical vapor deposition in the fluidized bed." Berlin Pro Business, 2005. http://deposit.ddb.de/cgi-bin/dokserv?id=2689065&prov=M&dok_var=1&dok_ext=htm.
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Richards, Robert William. "The high temperature behaviour of hot-dipped aluminised steels." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253522.
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Nelson, Nico. "An investigation into the feasibility of combined diamond and diamond-like carbon coatings for effective dry turning of aluminium alloys." Thesis, Brunel University, 2016. http://bura.brunel.ac.uk/handle/2438/13186.
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The efficacy of combined diamond and diamond like carbon coatings, to allow for effective and efficient dry turning of aluminium alloy Al 6082, has been investigated. Optimised diamond and diamond-like carbon (DLC) coatings were combined and deposited onto a WC-Co insert using chemical vapour deposition (CVD) methods. DLC coatings were developed by testing the effects of bias voltage, deposition time and gas pressure. During the development of the DLC layer, the effects of substrate geometry and positioning in the deposition chamber were investigated. It was discovered that coating characteristics could vary significantly across the samples as a result of geometrical effects. This contradicted claims that, as plasma enhanced CVD is a non-line of sight deposition method, any variation in the coating due to geometry would be negligible. SEM analysis revealed coating thickness to increase by over 50%. AFM measurements showed coating roughness to increase by up to 30 times, whilst Raman spectroscopy highlighted a significant decrease in sp3 bonding. This variation in characteristics was seen, through the use of scratch testing, to translate into significantly reduced tribological performance. Friction was increased by 60% and critical load was only half of that of the coating applied to flat surface. The combined coatings were characterised and machining performance was evaluated. Coating characteristics were examined using SEM, AFM and Raman spectroscopy. Cutting trials designed to simulate the expected tool life were conducted. Micro and nano-crystalline diamond coatings, with and without an additional DLC layer were trialled along with a single layer DLC coating. Commercially available uncoated and TiN coating inserts of identical geometry were also trialled as a reference. The results showed that the addition of the DLC layer effectively reduced the roughness of the diamond, however, this did not translate into reduced adhesion of the aluminium to the cutting tip. It has been shown that for this particular machining scenario, a smoother coating effectively increased friction and adhesion of the workpiece material. The investigation has highlighted that due to the complex dynamics of material transfer effects in sliding, it cannot be assumed that a smoother surface layer will lead to improved tribological performance.
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Kucita, Pawee. "The development of a wear resistance aluminium bronzes (Cu-Al-Fe) coating." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/403720/.
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Aluminium bronze alloys (Cu-Al-Fe) with Al > 14 wt. % are known to have high wear resistance and low friction coefficient against ferrous metals thus making it an ideal material for forming dies application. However, the use of these alloys has been restricted by the high cooling rate required to prevent embrittlement of the alloy during production. The plasma transferred arc technique (PTA) is an attractive production technique that offers the required high cooling rate, however the resulting microstructure is strongly dependent on the composition change induced during deposition. Therefore to optimise the microstructure for application such as forming dies, thorough understanding of the effects of PTA induced composition change on the microstructure, wear and corrosion resistance properties are required. The composition change induced by PTA involves primarily an increase in Fe. Therefore, in the present research four aluminium bronze coatings with 9, 20, 27 and 35 wt. % Fe were produced from a gas atomized Cu-Al-Fe powder by deposition on to an E.N. 10503 steel substrate by PTA. Microstructure characterisation was carried out using complementary techniques involving SEM, EDS, XRD, EBSD and depth-sensing nano-indentation on etched and electro-polished specimen. The results show that Fe content above 9 wt. % leads to a phase change from the Cu3Al martensitic β1' to solid solution (Cu) phase. This is also accompanied by an increase in size of the Fe3Al intermetallic κ1 phase. The redistribution of Al solute during cooling was identified as the main factor for the observed phase change. These microstructure changes lead to a hardness increase from 4.9 GPa in the coating with 9 wt. % Fe to 5.6 GPa in the coating with 35 wt. % Fe, however hardness mapping using depth-sensing nano-indentation shows that in the high Fe content coating, the hardness distribution is not uniform. This is due to the large volume fraction of the intermetallic κ1 phase which has high hardness of ~7 GPa. The wear resistance of the coating was found to be strongly influenced by the Cu-rich matrix phase. In the coatings with 20, 27 and 35 wt.% Fe, delamination and abrasive wear are the dominant wear mechanisms. SEM observations show that pile-up of slip at the hard intermetallic phase leads to the formation of surface cracks. Coalescence of these cracks coupled with the adhesion between the coating and the ferrous counter material were found to be responsible for promoting delamination wear, which results in high wear rate. The coating with 9 wt.% Fe has the lowest specific wear rates of 2.11-2.87 x 10-4 mm3/Nm against AISI 316, 420 and 440 stainless steel. This is significantly lower than the specific wear rates of 5.95-15.36 x 10-4 mm3/Nm measured for the currently used AISI D2 tool steels at the same condition. This is due to the uniform hardness and retention of the martensitic β1' phase. The effects of PTA induced microstructure change on the corrosion resistance were investigated by electrochemical and immersion corrosion tests in an aerated 3.5 % NaCI solution. The results show that the corrosion resistance of the coating is strongly dependent on complete formation of Al2O3 protective layer. The Al content in the coating is a critical factor in the formation of the protective layer. In the coating with high Fe content where limited Al solutes are available, high corrosion rates of 300-400 x 10-3 mm per year were observed. The 9 wt.% coating which contains the highest Al solute, the lowest corrosion rate of 22.5 x 10-3 mm per year was measured. This corrosion rate is comparable to the more expensive and highly alloyed nickel aluminium bronze. Based on the results obtained in the present research, the coating with a martensitic β1' phase and submicron size intermetallic κ1 phase has the highest wear and corrosion resistance. Such a structure can be achieved by controlling the PTA parameters to minimize the composition change promoted by melting of the steel substrate during deposition. The results from the present research also highlight the importance of interface properties, which have been shown to have a significant influence on properties such as adhesion, wear and corrosion. As more composite materials are utilised, further understanding of the microstructure and properties near the interfaces between materials becomes ever more important. It is hoped that the methodology and results presented in this thesis will provide the initial groundwork for future experimental and modelling work on multiphase material.
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Ganeshamurugan, Subramaniam. "Synthesis and evaluation of novel buffer/hole-injecting oligo(9-aminoanthracene)(s) in aluminium quinolate organic electroluminescent devices (OELDs)." Thesis, London South Bank University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271761.
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Piippo, Juha. "Electrochemical characterization of inorganic coatings : titanium nitride and aluminium oxide coatings characterized using electrochemical impedance spectroscopy /." [S.l.] : [s.n.], 1993. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10309.
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Court, Spencer. "Characterisation of electroless nickel coatings on aluminium and steel substrates." Thesis, University of Portsmouth, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247064.
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Coward, M. I. E. "Vanadate - based conversion coatings for the aluminium alloy 2014A - T6." Thesis, Loughborough University, 2002. https://dspace.lboro.ac.uk/2134/7591.
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The aluminium alloy 2014A-T6 is used as an aerospace alloy due to its strength and rigidity. The disadvantage of this alloy is that it is susceptible to galvanic corrosion, this occurs due to the fact that the main alloying element, copper, forms discreet precipitates principally of CuAl2 which are noble to the main aluminium matrix. One of the main ways in protecting the alloy from corrosion is by the application of a passive chromate conversion coating. Due to legislation, chromates are being outlawed, so replacements are being sought Investigations into sodium orthovanadate as an alternative conversion coa ing, showed that it provided a degree of protection against chloride ion attack from both salt spray testing and immersion in 3.5% sodium chloride. Tests were carried out to see if coating of the copper intermetallic could reduce the amount of galvanic attack the 2014A-T6 Al alloy was subjected to. Investigations were carried out in to the inhibition the copper surface by the use of sulphur-based compounds. The results showed that inhibition did not occur. However, further investigations into organic acids such as sebacic acid showed that when added to the sodium orthovanadate solution they promoted greater corrosion protection by reacting with the alkaline sodium orthovanadate solution to form sodium sebacate. The sodium sebacate was able to block cracks on the coating surface thereby inhibiting ingress of chloride ions to the surface of the 2014A-T6 Al alloy. This was proved by the use of scanning electron microscopy, which showed the presence of fine needle like features of precipitated sodium sebacate. X-ray photoelectron spectroscopy results showed that there was a high possibility that sodium sebacate was present on the surface due to the presence of both carbon and sodium which were not present when the alloy was treated from a solution containing just sodium orthovanadate. A variety of coatings were analysed using D. C. electrochemical polarisation, it was found that the sodium orthovanadate treatment, containing the sebacic acid, gave a considerable increase in the corrosion resistance in 3.5% NaCl compared to all other coatings except chromate. However, the sodium orthovanadate coating containing sebacic acid showed a reasonably close corrosion. resistance to the Alochrom 1200 chromate coating when subjected to salt spray corrosion tests. Simulated samples of 2014A-T6 Al alloy were produced by coupling laboratory produced CuAl2 and commercially produced aluminium. The results obtained using D. C. electrochemical polarisation gave similar trends to that obtained by a commercial sample of 2014A-T6 Al alloy showing that the sodium orthovanadate/sebacic acid coating solution was highly effective. This was backed up by the use of zero resistance ammetery which showed that the sodium orthovanadate/sebacic acid at 60 seconds at 60°C showed broadly comparable results with chromates up until 190 hours, when the coated couples were immersed in 3.5% NaCl at 25°C.
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McCloskey, Margaret Ann. "Plastic instability of platinum modified and unmodified aluminide coatings during 1100 C cyclic testing." Thesis, Monterey, California: U.S. Naval Postgraduate School, 1987. http://hdl.handle.net/10945/22420.
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Chandio, Ali Dad. "Processing, characterisation and oxidation study of the nickel aluminides (βNiAl) for thermal barrier coating applications." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/processing-characterisation-and-oxidation-study-of-the-nickel-aluminides-nial-for-thermal-barrier-coating-applications(36f4ed36-5df2-47ab-bf0f-6ecaab19d9f4).html.
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Superalloys used in aeroengines are designed to offer superior strength at increasingly higher operating temperatures. In order to optimise the working efficiency and provide additional protection to the components such as turbine blades; a thermal barrier coating (TBC) system is applied. The TBC is a multilayer system consisting of mainly two layers i.e. bond coat (BC) and topcoat (TC). In addition, a third layer grows between the TC and BC during oxidation known as a reaction layer or thermally grown oxide (TGO). The function of the TC (usually, yttria stabilised zirconia (YSZ)) is to provide thermal insulation to aeroengine parts or reduce their surface temperatures; whereas, the BC provides binding between the TC and the substrate, and oxidation resistance to the underlying alloy by forming an adherent and continuous oxide i.e. α-Al2O3. During service, in the absence of mechanical damage to the TBC, most failures are attributed to the BC performance. The most frequently adopted BCs are; β-(Pt, Ni)Al, Pt-γ-Ni/γ’-Ni3Al and MCrAlY. In addition, reactive elements (REs) are incorporated in the BCs due to their ability to enhance oxidation resistance significantly. In the present study βNiAl based coatings/BCs and alloys with and without REs (Zr and Hf) and Pt were prepared. For the coatings CMSX-4 single crystal superalloy was used as a substrate material and pack aluminising/cementation or in-situ chemical vapour deposition (CVD) as a coating process. The isothermal oxidation testing was carried out at 1150oC for 50 and 100 hours in air. The preparation and oxidation performance of a δNi2Al3 coating was carried out, as, this is a starting material for βNiAl matrix based coatings/or BCs. The oxidation of δNi2Al3 coating showed large volumetric changes (thickness variations), multiphase TGO, TGO/coating interface melting and spallation during oxidation. In contrast, the ‘simple βNiAl’ coating (or βNiAl matrix) was found to exhibit comparably enhanced thermal stability than that of the δNi2Al3 coating. Moreover, a detailed study of the simple βNiAl coating was also carried out in order to understand the oxidation performance. The coating before oxidation in the as-deposited condition was found to contain residual compressive stresses of 140 – 200 MPa. In contrast, after oxidation analysis exhibited substantial interdiffusion between the coating and the substrate resulting in a large reduction of the Al content and influx of substrate elements into the coating. This in turn caused coating transformation from βNiAl to the γ’-Ni3Al phase and formation of a multiphase TGO (TiO2, NiAl2O4, and ϴ-Al2O3 intrusion in α-Al2O3). Moreover, the degree of the TGO spallation and residual stresses increased with the oxidation time. In order to enhance the oxidation performance of the βNiAl coatings, the substrate pre-treatment was carried out i.e. CMSX-4 superalloy was electrolytically etched to remove the γ-Ni phase and fabricate βNiAl coatings on the remaining γ’-Ni3Al. This coating is termed as E-βNiAl. In comparison to simple βNiAl, the E-βNiAl coating showed improved spallation resistance. However, E-βNiAl revealed increased surface area due to etching of the substrate and triggered fast TGO growth rates when tested in an un-polished condition. Furthermore, simple βNiAl coatings were doped with Zr and Hf separately using a two-step aluminising method. The appropriate addition of either Zr or Hf was found to reduce the substrate elements (W, Ta, Cr and Ti etc.) in the coating before and after oxidation. After oxidation, examination of the presence of Zr or Hf in the coating was found to confirm the commonly reported beneficial effects. The TGOs grown on these coatings were almost pure α-Al2O3 which subsequently reduced growth and stresses. In addition to Zr/& Hf doped coatings, a study on Hf and Zr doped βNiAl bulk alloys was also carried out in order to understand the dopant effects on the oxidation resistance of βNiAl alloys in the absence of interdiffusion (as in case of coatings). In general, the commonly reported oxidation benefits were confirmed by the addition of these elements such as reduced TGO growth, oxide pegging, a columnar morphology of the TGO and segregation of REs at alumina grain boundaries etc. In addition, two more beneficial effects are suggested to be the ‘TGO crack filling up (or crack-healing)’ and formation of the ‘dense-TGO’. Within this study, the investigation of commercially available Pt-βNiAl BC was also carried out in air and vacuum atmospheres. The results demonstrated that the initial chemistry and elemental distribution (particularly Al/& Pt) was found to affect the TGO growth and phases significantly. In addition to its well established beneficial effects, the main effect of a Pt addition is suggested to be the stabilisation of the βNiAl structure even at a lower Al content.
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Grilli, Rossana. "Conversion coatings for aluminium alloys : a surface investigation for corrosion mechanisms." Thesis, University of Surrey, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520579.
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Sears, Joanne Marie. "An investigation of aluminium-magnesium-cerium alloy coatings for corrosion protection." Thesis, University of Salford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365974.
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Tan, KengSoong. "Electrochemical analysis of the erosion corrosion of HVOF aluminium bronze coatings." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274707.
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