High temperature oxidation behavior of a high Al-containing ferritic heat-resistant stainless steel

The high temperature oxidation behavior of a high Al-containing ferritic heat-resistant stainless steel at temperatures of 800, 900, and 1000 degrees C in air were studied in isothermal oxidation tests. The results showed that the isothermal oxidation kinetic curves obtained at different temperatures followed the parabolic law, and the weight gain per unit at 1000 degrees C was significantly higher than that at 800 and 900 degrees C. The oxidation rate at 1000 degrees C was about three times faster than that at 800 and 900 degrees C. Continuous and compact multicomponent oxide films mainly composed of Cr2O3, Al2O3, spinel MnFe2O4, and MnCr2O4 were obtained at 800 and 900 degrees C. The oxide film started delaminating at 1000 degrees C; the outer layer was composed of Cr2O3, spinel MnCr2O4, and MnFe2O4, the middle layer was composed of Fe2O3 and Fe-Cr matrix, and the inner layer was composed of Al2O3 and SiO2. Oxidation resistance at 1000 degrees C was reduced mainly because of porous Fe2O3 and inner oxidation of Al and Si. In addition, the oxidation mechanism was discussed based on kinetic and morphological observations.