High Temperature Oxidation Resistance of Solid-Solution and Gamma-Prime Strenghthened Alloys in the Presence of Water Vapor

Water vapor often present as a by-product in many combustion environments is known to accelerate oxidation rate of wrought high-temperature alloys. This paper is focused on the comparative cyclic oxidation resistance of several solid-solution- and gamma-prime-strengthened alloys in humidified air. The oxidation testing included 1,008 hour exposures at 760^oC and 871^oC in air with 10 vol. % H₂O. Additional testing involved oxidation exposures of selected solid-solution-strengthened alloys in air with 20 vol. % H₂O at 760^oC and 871^oC. Alloy performances were ranked by assessing weight-change behavior and metal recession measurements which includes metal loss, average internal penetration, and maximum internal penetration. The types of oxide scales formed in the presence of water vapor were studied using SEM equipped with EDS. The role of alloy composition on the scale formation will also be discussed in detail. In general, it was found that the alumina-forming alloys exhibited superior performance compared to chromia-forming alloys. Among chromia-formers, alloys with high Fe contents were found to be susceptible to increased oxidation attack.