High Temperature Oxidation of SUS430 in H<SUB>2</SUB>O-Containing Atmospheres at 1473 K

In order to clarify the influence of H2O vapor on growth behavior and morphology of scales formed on a stainless steel, SUS430 steel was oxidized for up to 3600 s at 1473 K in (N2-3%O2)-H2O atmospheres. The H2O contents were regulated to 6.9, 19.7, and 45.4%(vol%). The scale morphology showed that a uniform Cr2O3 scale formed in the initial stage, followed by the formation of iron-rich oxide nodules. Finally, the external scale of Fe2O3 and Fe3O4 and the porous inner scale of Fe(Fe, Cr)2O4 covered the entire specimen surface. The growth of the external and inner scales followed a linear rate law, and the thickness of each scale increased linearly with increasing H2O content. These results indicate that external and inner scales formed in H2O-containing atmospheres have high porosity and the formation of the inner scale is due to diffusion of H2O through the porous external scale.