Comportement mécanique d'alliages pour couches de liaison de barrière thermique par microindentation instrumentée à haute température

Abstract : Thermal 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
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Arnaud Villemiane. Comportement mécanique d'alliages pour couches de liaison de barrière thermique par microindentation instrumentée à haute température. Autre. Institut National Polytechnique de Lorraine, 2008. Français. ⟨NNT : 2008INPL112N⟩. ⟨tel-01753027⟩

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