Effect of γ’ Precipitate Size on the High Temperature Oxidation Resistance of Alumina-Forming γ + γ’ Two-Phase Alloys

Abstract

The effect of microstructure, particularly precipitate size, on the high-temperature oxidation behavior of a Ni–10Cr–14Al–0.05Zr alloy with a γ + γ’ two phase structure was systematically investigated in this study. The size of the γ’ precipitates was found to influence both the initial oxidation behavior and the transition to the formation of a protective Al₂O₃ scale. Specimens with fine precipitates formed a homogeneous but less protective thick oxide scale, whereas those with coarse precipitates exhibited two distinct oxidation behaviors associated with the γ and γ’ phases. The transition to protective oxidation tended to occur earlier in specimens with fine precipitates, likely due to the enhanced outward diffusion of Al resulting from the higher density of γ/γ’ interfaces, which act as preferential site for decomposition. Once a continuous protective oxide scale had formed, precipitate size had limited effects on the high-temperature oxidation behavior.