Oxidation behavior of Fe-20Cr-25Ni-Nb austenitic stainless steel in high-temperature environment with small amount of water vapor

•Fe-20Cr-25Ni-Nb steel was corroded in an oxidizing environment at 1000 °C.•An accelerated oxidation occurs for this steel after a transition point.•Oxidation of Fe2Nb phases promotes the formation of the re-generated Cr2O3 phases.•Growth of re-generated Cr2O3 induces the cracking and spallation of oxide scale. The oxidation behavior of a Fe-20Cr-25Ni-Nb austenitic stainless steel was investigated in an oxidizing environment at 1000 °C. Results show that an accelerated oxidation occurs after a transition point and some oxide nodules with two layers are formed on the steel surface. The oxidation of intergranular Fe2Nb phases can induce micro-cracks and promotes the formation of re-generated Cr2O3 phases. The formation and growth of the re-generated Cr2O3 phases are related to the cracking and spallation of the oxide scale, which result in the formation of these oxide nodules and the associative accelerated oxidation.