High‐Temperature Oxidation of Fe–Si Alloys in Atmospheres Containing 2.0% SO₂ + 5.0% O₂

Abstract

The microstructure and composition of the scales formed are examined after being exposed to atmosphere containing 2.0% SO2 + 5.0% O2 for 60 min in the temperature range of 900–1200 °C. The composition of the scale post‐oxidation primarily varies with temperature rather than silicon content. FeS exhibits a melting temperature of 950 °C, whereas FeSi2O4 melts at 1150 °C. Two mechanisms for FeS formation are proposed. Eutectoid transformation of molten FeS occurs during subsequent cooling, resulting in lamellar FeS + Fe–S–O compounds. Above 1150 °C, the melt of Fe2SiO4 further increases the Fe diffusion rate. This dual‐liquefaction mechanism involving FeS and Fe2SiO4 accounts for the anomalous oxidative mass gain observed in Fe–Si alloys exposed to a sulfur‐containing atmosphere.