High Temperature Oxidation of SUS430 in H₂O-Containing Atmospheres at 1473 K

Abstract

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.