Abstract
The oxidation resistance of β-NiAl diffusion coating deposited on selected Ni-based superalloys with commercial grades has been investigated. Emphasis has been placed upon oxide microstructure and oxidation kinetics. It is shown that the presence of sufficient concentration of Hf in the superalloy substrate has the effect of decelerating the kinetics of Al2O3 growth as well as improving its adhesion to the substrate. On the other hand, the Hf effect appears to outweigh the possible detrimental effects of both Ti and precipitates of α-Cr near the coating surface. Conversely, the results indicate that in the absence of Hf, the oxidation resistance is degraded by the combined detrimental effects of both Ti and α-Cr, which are reflected by higher oxide growth rate and poor adhesion.
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