Design of a novel oxide@h-BN core-shell structure in stainless steel towards superior corrosion and wear resistance

Abstract

High corrosion- and wear-resistant stainless steels are highly sought after for demanding marine structural applications. However, most stainless steels with high hardness or outstanding self-lubrication exhibit inferior corrosion resistance, and vice versa. In this study, we propose a strategy for wrapping oxide inclusions with the lubricating phase h-BN through in-situ nitrogen alloying in B-bearing stainless steel, forming a novel oxide@h-BN core-shell structure. The oxides exhibited constrained growth within the h-BN shell, which reduced the particle size and increased the number density. This modification enhanced dispersion strengthening, yielding a composite material hardness of 728 HV_0.5. The h-BN functioned as a solid lubricant during the wear process, significantly lowering the friction coefficient. Additionally, the high electrical insulation and chemical stability of h-BN effectively separated the oxides from the surrounding matrix, thereby preventing pitting corrosion, which is typically associated with oxide dissolution. The increased nitrogen content in the solid solution also enhanced the content of Cr₂O₃ and CrN in the passive film, thereby improving its stability and protective capabilities. As a result, the corrosion resistance of this alloy was nearly comparable to that of 316 L stainless steel, whereas its wear performance surpassed that of M2 tool steel. Our findings offer valuable insights into the design of high-performance stainless steels.