Synergistic regulation of mechanical properties and pitting corrosion resistance of high-nitrogen austenitic stainless steel via vanadium microalloying

The addition of vanadium substantially enhances the strength of the high-nitrogen austenitic stainless steel (HNASS), while maintaining excellent ductility and pitting corrosion resistance. The effects of vanadium microalloying on the microstructure, mechanical properties, and pitting resistance of HNASS were systematically analyzed with a focus on the role of VN during the pitting process. The results suggest that vanadium promoted the precipitation of VN, contributing to grain boundary pinning and grain refinement. As vanadium content increased, the number of precipitates rose, and the average grain size decreased. At lower vanadium content (0–0.2 wt.%), the strength of the material was significantly reinforced with increasing vanadium content, while maintaining excellent ductility and pitting resistance. However, when the vanadium content reached 0.3–0.4 wt.%, precipitates demonstrated a substantially increased number and coarsened, accompanied by the formation of numerous dislocations around the precipitates. This brought about further strength reinforcement but a marked decline in ductility and pitting resistance. Additionally, pitting corrosion was initiated at the matrix–VN interface. Compared to the matrix, VN exhibited higher reactivity and preferentially reacted with Cl⁻ ions, provoking dissolution. However, NH₄⁺ generated during the dissolution of VN facilitated repassivation of the material, suppressing further pitting propagation.