Investigation into the failure mechanism of chromia scale thermally grown on an austenitic stainless steel in pure steam

• High temperature corrosion of HR3C was studied in pure steam at 700 °C.
• Cracking and buckling of chromia scale thermally formed in pure steam was observed.
• Failure mechanism of chromia scale thermally grown in pure steam is proposed.

The corrosion behavior of a commercial austenitic stainless steel HR3C was investigated in air and in pure steam at 700 °C, and the results are compared. The results show that the chromium concentration in HR3C was sufficient to form protective chromia scale initially in both environments. The oxide scales thermally grown in pure steam, however, were apt to lose their protectiveness by cracking and buckling. A failure mechanism of chromia scale thermally grown in pure steam is proposed by considering influences of hydrogen produced during steam oxidation in terms of molecular hydrogen and hydrogen defects.