Effect of Water Vapor on Alumina Scale Growth Based on First-Principles Calculations

Despite much effort directed at elucidating the impact of water vapor on the high-temperature oxidation behavior of metallic materials, a complete understanding of its atomistic mechanisms remains elusive. Using first-principles calculations based on the density functional theory, here we elucidate the effect of water vapor on the formation, migration, and aggregation of atomic defects in α-Al2O3, γ-Al2O3, and θ-Al2O3, the three dominant aluminum oxide phases involved in the high-temperature oxidation of alumina-forming alloys. These results reveal the atomic origins of water vapor in inducing faster alumina scale growth compared with dry oxygen and suggest ways of manipulating the oxidation kinetics of alumina-forming alloys via controlling the oxidizing atmospheres.