Revealing the oxidation mechanism of 310S stainless steel in supercritical water via high-resolution characterization

Abstract

This work studied the surface oxide scale of 310S stainless steel exposed to 650 °C supercritical water for 1000 h. The oxide scale showed a complex structure with an outer oxide layer, an inner oxide layer, and a much thinner Cr2O3 layer. The outer oxide layer consisted of Fe2O3, NiFe2O4 and NiO. Fe-Cr-Ni spinel was identified in the inner oxide layer due to internal oxidation. Transition from internal to external oxidation occurred at the metal-oxide interface, resulting in the formation of a protective Cr2O3 layer. The formation mechanisms of each oxide layer were discussed.