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Étude du comportement en oxydation de nouveaux revêtements en aluminiure de nickel dopé au zirconium. Application aux barrières thermiques

Sarah Hamadi
Abstract : Aeronautical turbine blades are used in an extreme environment. Indeed, they are located at the combustion chamber exit and are then exposed to hot oxidising gases. They are made of a nickel based superalloy protected either with an alumina-forming coating, or with a thermal barrier system. In this system, the superalloy is protected thanks to an alumina-forming bondcoat and a yttria partially stabilised zirconia insulating layer. When exposed to the combustion gases, a protective alumina layer grows on top of the nickel aluminides. The industrial system involves a platinum modified NiAl that improves the adhesion of the thermally grown oxide. But the processing costs are to be reduced. The reactive elements (including Zr) are known to improve the alumina adhesion on the nickel aluminides, but the mechanisms involved in Zr-doped coating are still to be investigated. This study has been mainly focused on the NiAl and NiAl(Zr) coatings. We noticed that the zirconium is mobile in the whole system, it delays the coating ageing and avoid the presence of cavities at the metal/thermally (1100°C) grown oxide interface. We performed experiments to understand the role of zirconium on the cyclic oxidation resistance and they revealed that this doping element mainly modifies the first stages of oxidation by favouring the formation of alpha alumina. This influence of Zr on the short-time oxidation doubles the lifetime of the systems exposed to cyclic oxidation at 1100°C. Some experiments using NiAl(Zr) as a bondcoat in the thermal barrier system are also reported.
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Submitted on : Wednesday, June 16, 2010 - 8:00:00 AM
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Sarah Hamadi. Étude du comportement en oxydation de nouveaux revêtements en aluminiure de nickel dopé au zirconium. Application aux barrières thermiques. Chemical Sciences. Université Pierre et Marie Curie - Paris VI, 2009. English. ⟨pastel-00006150⟩

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