Oxidation Performance of NiCoCrAlYTa + 7YSZ Coatings With Ta Addition at Different Temperatures

ABSTRACT This study investigates the morphology and oxidation behavior of thermally grown oxides (TGO) formed at the interface of NiCoCrAlYTa + 7YSZ (7 wt% Y 2 O 3 ‐stabilized zirconia) coatings deposited by air plasma spray (APS) in air environments at 1050°C, 1100°C, and 1150°C. The enrichment of Ta‐rich oxides beneath the TGO, along with the segregation of Y and Ta at Al 2 O 3 grain boundaries, effectively inhibited the outward diffusion of Al. During cyclic oxidation, the outward diffusion of Al is influenced by the content of Y and Ta elements. Dense fine‐striped Al 2 O 3 formed within the BC during the APS process, acting as a diffusion barrier to inhibit the outward diffusion of Al. The internal growth oxides generated during cyclic oxidation significantly reduced the coefficient of thermal expansion (CTE) of the bond coat (BC), thereby reducing the driving force for top coat (TC) spallation and extending the service life of thermal barrier coatings (TBCs).