Effects of Cr and Mo on precipitation behavior and associated intergranular corrosion susceptibility of superaustenitic stainless steel S32654

Highlights: • Effects of Cr and Mo on driving force and element activity were clarified. • Increasing Cr and Mo contents significantly promotes the precipitation of σ phase. • Raising Cr and Mo contents remarkably enhances the intergranular corrosion susceptibility. • Mo has stronger promotion effect on precipitation and intergranular corrosion susceptibility. • Intergranular corrosion is mainly caused by Cr- and Mo-depleted zones around precipitates. -- Abstract: The effects of Cr and Mo on the precipitation behavior and associated intergranular corrosion susceptibility of S32654 were investigated by microstructure characterization, thermodynamic calculation and electrochemical measurement. Increasing Cr and Mo contents significantly promoted the formation of σ phase and inhibited the precipitation of R, π phase and Cr₂N. Mo has stronger promotion effect on the formation of σ phase than Cr. The effects of Cr and Mo on the precipitation behavior were mainly achieved by affecting the driving force for precipitation and the activity of elements. The specific influence mechanism has been fully discussed in this paper. Additionally, the promotion effect of Cr and Mo on precipitation further expanded the area of Cr- and Mo-depleted zones around various precipitates, enhancing the intergranular corrosion susceptibility of S32654.