Effect of microstructure on early oxidation of MCrAlY coatings

This study investigates the early oxidation behavior of two MCrAlY coatings, with identical nominal compositions but differing microstructures, deposited on Hastelloy® X superalloy substrates through low pressure plasma spraying (LPPS) and high velocity oxygen fuel (HVOF) techniques. The coatings were subjected to oxidation at 1150 °C, where it was found that the LPPS coating, containing relatively coarse grains, exhibited distinct oxidation behaviors for the γ and β phases. Specifically, the oxide formed on the γ phase developed a multi-layer structure comprised of an outer layer of (Ni,Co)(Cr,Al)2O4, an intermediate layer of (Cr,Al)2O3, and a dense inner layer of α-Al2O3. In contrast, the β-phase displayed a more uniformly compacted oxidation across the coating surface. The findings suggest that microstructural differences significantly influence the oxidation resistance of MCrAlY coatings, highlighting their potential implications for enhancing the durability of protective coatings used in high-temperature applications.