Inhibition of the second phase precipitation and improvement of intergranular corrosion resistance by boron segregation at the grain boundary of S31254 superaustenitic stainless steel

Abstract

The inhibition of Mo segregation and phase precipitation is vital for improving the hot workability and corrosion resistance of superaustentic stainless steels (SASS). The boron non-equilibrium segregation of S31254 SASS was implemented through solid solution, air cooling, and diffusion at low-temperature treatment (SADT). The precipitation process and intergranular corrosion (IGC) of S31254 SASS with various boron distributions were researched at a sensitive temperature. The second phases were observed and identified by SEM and TEM. IGC susceptibility was evaluated by double-loop potentiodynamic reactivation (DL-EPR) measurements. The SADT treatment promoted more segregation of B at the grain boundary, leading to lower amounts of grain boundary precipitation before aging for 6 h. The decrease of σ phases in B-regulated samples enhances the IGC resistance, compared with the samples without B addition specimens.

Keywords

• Superaustenitic stainless steel
• S31254
• Boron
• Sigma phase
• Corrosion