Adhesion of thermal barrier coatings systems after long term oxidation : influence of preoxidation temperature and surface state of the bond coat
Résumé
The aim of this study was to determine the effect of the pre-oxidation temperature and surface state of the bond coat on the microstructure of the oxide scale formed at the first stages of oxidation and on its adhesion after subsequent long-term oxidation (1000 h) at 1100°C. Short-term isothermal oxidations of 1 h were performed at several temperatures (900°C, 1100°C) on a Pt-modified NiAl bond coat with two different surface states (as-aluminized or grit-blasted) deposited on a superalloy (AM1). The adherence of the different systems after an additional isothermal ageing treatment in air at 1100°C for 1000 h, was compared in order to deduce the initial oxide scale leading to the best resistance to spallation. Characterization was performed using SEM and analytical TEM. The crystalline structure and the morphology of the as-formed oxide scale were studied as a function of the different parameters.