Formation of Si Diffusion Layer on Stainless Steel by Pack Cementation Method and High Temperature Corrosion Resistance

摘要

Si diffusion layers on SUS 310 steel surfaces were formed by halide-activated pack cementation, and their high temperature corrosion resistance was evaluated. The Si diffusion layers formed in the sample surfaces consisted of an inner layer and an outer layer. The inner layer contained 11 approx 12 mass percent Si was uniform and adhesive to the substrate metal. It was found from XRD analysis, that the inner layer consisted of two phases of alpha-Fe and Cr_3Ni_5Si_2. The thickness of the inner layer increased with an increase in the treatment time and a rise in the treatment temperature. The inner layers of 60 approx 80 mu m thickness were obtained by the treatments for more than 28.8 ks at 1223 K. The results of high temperature corrosion experiments showed that the corrosion resistance of the sample having Si diffusion layer was greatly improved by the formation of a protective inner scale consisting of SiO_2.