Combined experiment and first-principles study of the formation of the Al2O3 layer in alumina-forming austenitic stainless steel

Abstract

A combination of experiment and first-principles research on the formation of the Al₂O₃ layer in alumina-forming austenitic stainless steel is presented. The results show that the oxide layer has a multilayer structure with an outer oxidized Cr₂O₃ and an inner Al₂O₃. Further, theoretical simulation using the first principles method is applied to research the formation process of the Al₂O₃ layer in the Fe/Cr₂O₃ interface as well as the impact of four alloying elements (Cr, Ni, Mn, and Si) on the formation of Al₂O₃. Results indicate that the Al atom originating from the Fe-based matrix prefers to diffuse into the Cr₂O₃ slab, thereby resulting in the formation of the Fe/Al₂O₃/Cr₂O₃ construction, which agrees with the experimental behaviour. Moreover, the introduction of Cr, Ni, Mn, and Si can slow down the diffusion of Al and result in a slower growth rate of Al₂O₃. The effects of Cr–Y (Ni, Mn, and Si) co-doping are more significant than those of X (Cr, Ni, Mn, and Si) single doping. Furthermore, Si can improve the adhesion of the Fe/Al₂O₃/Cr₂O₃ interface, thus can improve the adhesion of the oxide scales.