Effects of zirconium and oxygen on the oxidation of FeCrAl-ODS alloys under air and steam conditions up to 1500 °C

Effects of Zr and excessive oxygen addition on the oxidation behavior of FeCrAl-ODS alloys are evaluated by high-temperature air and steam oxidation tests together with analyses using the thermochemical multiphase computer software FactSage. Zr addition to improve the strength of FeCrAl-ODS alloys increases the oxidation rate, but the oxidation rate can be reduced by increasing the excessive oxygen content to the appropriate level. From thermochemical multiphase calculations, Zr activity becomes lower in the alloy matrix with increasing excessive oxygen, and preventing ZrO₂ formation within the alumina scale can decelerate oxygen inward diffusion through ZrO₂. Addition of Zr and excessive oxygen can also improve adhesion of the alumina scale at 1400 °C. Once the protective alumina scale is lost during oxidation at 1500 °C, Fesbnd O direct reaction with exothermic heat takes place and an oxidation reaction with partial melting rapidly proceeds within 30 min.