Effect of N and Mo Contents on Precipitation Behavior, Intergranular Corrosion Resistance, and Mechanical Properties of Super Austenitic Stainless Steel

Abstract

High‐Mo super austenitic stainless steels are prone to precipitate Cr‐ and Mo‐rich σ phases during hot working, which severely impairs their corrosion resistance and mechanical properties. To regulate precipitation, maintain corrosion resistance, and enhance strength, the key lies in rationally controlling the N/Mo ratio. In this study, the precipitation behavior and resultant properties of a conventional S31254 specimen and a specimen with an adjusted N/Mo ratio were comparatively investigated. The results show that in the compositionally modified specimen, the total amount of precipitates during high‐temperature aging is significantly reduced, the precipitates are more dispersed, and the proportion of the Laves phase increases. Moreover, no precipitates are observed even after aging at 1050 °C. This compositional adjustment effectively alleviates the formation of Cr‐depleted zones, and thus significantly improves the intergranular corrosion resistance of the material while simultaneously enhancing its mechanical properties. This study provides valuable insights for the alloy design optimization and performance improvement of super austenitic stainless steels.