Comparing the oxidation of FeCrAl alloys in isothermal and cyclic high-temperature steam environments

This study investigates the oxidation behavior of FeCrAl (APMT and C26M) alloys in high-temperature steam at 1000 °C using isothermal and cyclic conditions. The FeCrAl alloys exhibited a fully ferritic body-centered cubic structure with no significant phase transformation, and the manufacturing procedures of the alloys resulted in varying grain sizes and porosity. In the 5 h isothermal test, the protective alumina film provided corrosion resistance without cracking in the high-temperature steam environment. However, thermal cycling seemed to compromise passivity; expansion and contraction during heating and cooling allowed oxygen penetration into the underlying metal in local regions, leading to transgranular crack-like features. Spallation of oxides was also observed. Post-exposure analysis of the oxide film formed on the FeCrAl alloys revealed two distinct oxide layers on the alloy: an outer Al-rich oxide film and an inner mixed oxide enriched in Cr and Fe.