Water vapor is a major component of most combustion gas streams, and has been shown to generally
increase the rate of attack of heat-resistant alloys at elevated temperatures. The role of water vapor in causing
accelerated oxidation will be reviewed for a variety of alloys, including austenitic stainless steels, ferritic stainless
steels, and nickel-base superalloys. A variety of factors will be considered, including environmental variables
such as gas composition and temperature, alloy composition, and specimen thickness. Specifically, iron-base
alloys are more susceptible to increased degradation in humidified air, with the initial chromium content playing a
significant role in the transition from protective to rapid oxidation. Nickel-base alloys were observed to exhibit
altered oxidation kinetics, but did not form rapidly growing oxides.