Austenitization triggering breakaway oxidation of FeCr-base alloys at 900 °C

Journal article, 2025

Oxidation of Fe18Cr-X (X = Mo, Si) alloys in Ar-H2-H2O gas mixtures has been studied at 900 °C. The α-to-γ transformation at the Cr-depleted specimen edges is demonstrated to be the primary reason of breakaway oxidation. A diffusion analysis predicted protective behavior for ferritic (BCC) Fe-18Cr at 900 °C and loss of protection once austenite (FCC) is formed. Alloying Fe-18Cr with Si or coating with Ce resulted in a significantly lower oxidation rate and thus protective oxidation behavior while alloying with a ferrite stabilizing element (Mo) completely prevented breakaway oxidation not affecting the oxidation rate.