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.