Effects of sulfur pressure on the sulfldation behavior of Fe-Mo alloys at 700–900°C

Abstract

High-temperature sulfidation behavior of Fe-Mo alloys (containing 10 and 20 at.% Mo) was studied over the temperature range of 70000 °C above a pure sulfur pool with the sulfur-vapor of 102–105 Pa. The sulfidation kinetics followed the parabolic rate law in all cases. The corrosion rates increased with increasing temperature and sulfur pressure but decreased with increasing Mo content. The scales formed on the alloys were complex and bilayered, consisting of an outer layer of iron sulfide (FeS/Fe1 xS) and an inner heterophasic layer of mostly FeMo4S6, FeMo2S4, Fe1 xS, MoS2 (only detected at Ps2 = 105 Pa) and uncorroded Fe3Mo2. Platinum markers were located at the interface between the inner and outer scales, suggesting that the outer scale grew by the outward transport of an Fe ion and the inner scale grew by the inward S diffusion, as similar to the results in the literature.