Effect of Molybdenum Content on Microstructure and Corrosion Behavior of Rapid Hot‐Press Sintered High‐Nitrogen Austenitic Stainless Steel

To improve the corrosion resistance of high‐nitrogen austenitic stainless steel (HNS) fabricated by rapid hot‐press sintering (RHP), this study systematically examined the effects of molybdenum (Mo) additions of 1, 2, and 3 wt.% on its microstructure and corrosion behavior in a 3.5 wt.% NaCl solution. The results show that Mo does not completely dissolve into the matrix; instead, it forms Mo‐enriched particles with a core–shell structure, the number density of which increases markedly with increasing Mo content. At 1 wt.% Mo, the amount of Mo in solid solution significantly increased the interfacial charge–transfer resistance and promoted surface passivation, thereby providing the best corrosion resistance. In contrast, at higher Mo contents of 2 and 3 wt.%, excessive Mo‐rich particles tended to detach during the early stages of corrosion, resulting in the formation of micropores. These micropores promoted localized acidification, which in turn accelerated corrosion deterioration. Overall, 1 wt.% Mo is the optimal addition level, as it maximizes the beneficial effect on passivation while avoiding defects associated with segregation‐induced void formation.