High temperature oxidation of Fe-Cr alloys in atmospheres containing 2.0%SO2 + 5.0%O2

Abstract In this study, we examined the microstructure and composition of the scales formed after exposures from 825 °C through to 950 °C for 60 min in the atmosphere containing 2.0% SO2 + 5.0% O2 gas. The scale composition after oxidation mainly depends on temperature but not on the Cr content. The FeS formation temperature was 915 ℃, while its melting temperature was 925 ℃. Two mechanisms of the FeS formation are proposed. The eutectic transformation of molten FeS occurred during the subsequent cooling process, resulting in lamellar FeS + Fe-S-O compounds. The study indicated that Cr exhibits oxidation but not sulfidation resistance.