EFFECTS OF SULFUR PRESSURE ON THE SULFIDATION BEHAVIOR OF 310-STAINLESS-STEEL

High-temperature sulfidation behavior of 310 stainless steel was studi ed over the temperature range of 700-900 degrees C above a pure sulfur pool with the sulfur-vapor range of 10(-4)-10(-1) atm. The corrosion kinetics followed the parabolic rate law in all cases, The corrosion r ates increased with increasing temperature and sulfur pressure. The sc ales formed on 310 stainless steel were complex and multilayered. The outer scale consisted of iron sulfide (with dissolved Cr), (Fe, Ni)(9) S-8 and chromium sulfides (Cr2S3 and Cr3S4 With dissolved Fe), while t he inner layer was a heterophasic mixture of Cr2S3, Cr3S4, NiCr2S4, an d Fe1-xS. Platinum markers were found to be located at the interface b etween the inner and outer scales, suggesting that the outer scale gre w by the outward transport of cations (Fe, Ni, and Cr), and the inner scale grew by the inward transport of sulfur. The formation of Cr2S3, Cr3S4, and NiCr2S4 partly blocked the transport of iron through the in ner scale, resulting in a reduction of the corrosion rates as compared with the results in the literature.