Synergistic Effect of B and Y Micro-alloying on Oxide-Layer Formation on the Super-austenitic S31254 Stainless Steel

Aiming to address the Mo volatilization problem of super-austenitic stainless steel at high temperature, the S31254 steel containing B and rare earth element Y with high oxidation resistance was designed. It was observed that a synergy of B + Y can promote the formation of the dense Cr2O3 layer at 1050 and 1100 °C, making MoO3 layer formation difficult. While the oxide layers of the 0B sample from top to bottom were divided into four layers: Fe-rich oxide layer, MoO3 layer, Cr–Mn–Ni spinel oxide layer, and Cr2O3 layer (loose and porous), thus the undense Cr2O3 layer in the 0B sample can hardly inhibit MoO3 volatilization, especially at 1100 °C. In addition, the synergistic effect of B and Y on the diffusion of Cr to the surface was calculated using first-principles calculations. The results demonstrated that both the addition of B and Y can enhance Cr diffusion to the surface, while Y can specifically promote the combination of Cr and O. Consequently, the combined presence of B and Y exhibits a more favorable synergy for improving the density of the Cr2O3 layer, effectively inhibiting MoO3 formation and volatilization, thereby enhancing the oxidation resistance of S31254.