INTERNAL SULFIDE PRECIPITATION IN LOW CR-FE ALLOYS

The present article examines the internal sulfide precipitation in low Cr-Fe alloys that resulted from solid-state diffusion experiments at 600 degrees C. The internal sulfide precipitate microstructure is show n in alloys ranging from 11.3 wt pct Cr to 51.1 wt pct Cr. The diffusi on composition profile and sulfide phase compositions have been measur ed using electron probe microanalysis (EPMA). Based on the microprobe data and some calculations using established internal sulfidation theo ry, a description of the internal sulfide precipitation sequence and d epth is explained and the sulfide precipitate morphology is quantified . The solid-state diffusion experiments indicate that the optimum Cr c omposition range for sulfidation resistance at 600 degrees C is betwee n 20 and 40 wt pct Cr. The results have also been compared with existi ng low-temperature gas-solid sulfidation literature and the difference s in results are explained.