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

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.