Influence of Pre-treatment on the Growth Behavior of TGO on MCrAlY Bond Coat Surface

The thermally grown oxide (TGO), formed on the bond coat (BC) surface of thermal barrier coatings (TBCs), has a significant impact on the TBCs life time. In order to reduce growth kinetics of TGO, vacuum pre-treatment was taken for some bond coats before pre-oxidation and isothermal oxidation in air. The other bond coats were directly subjected to pre-oxidation and isothermal oxidation. The grain size and grain boundary distribution of the Al2O3 scale of all the bond coats with different heat treatments were analyzed by electron backscattered diffraction (EBSD). Element diffusion was taken into account to analyze growth kinetics of the TGO. Results indicate that the change of Al2O3 TGO thickness with isothermal oxidation duration doesn’t fit well to parabolic law as expected by conventional theory. It is attributed to the change of the grain structure during isothermal oxidation. This mechanism would benefit the development of long-life and highly reliable TBCs.