Influence mechanism of boron segregation on the microstructure evolution and hot ductility of super austenitic stainless steel S32654.

• B improves hot ductility of S32654 at 850–1150 °C but worsens that at 1200–1250 °C. • B segregation at GB detected by APT was the main reason affecting hot ductility. • B segregation inhibits Mo segregation and then σ phase precipitation at 900–950 °C. • B segregation promotes nucleation and inhibits growth of DRX grain at 1100–1150 °C. • B segregation enhances the liquefaction cracking tendency at 1200–1250 °C. Influence mechanism of B segregation on the microstructure evolution and hot ductility of S32654 at 850–1250 °C was systematically investigated through experimental research and theoretical calculation. The results demonstrated that the segregation of B at grain boundary (GB) played different roles in the microstructure evolution and hot ductility at various temperatures. At 850 °C, B segregation inhibited Mo segregation at the GB and enhanced the GB cohesion. At 900–950 °C, B segregation restricted the diffusion and segregation of Mo to the GB, inhibiting the precipitation of σ phase. At 1000–1050 °C, B segregation accelerated the dislocation accumulation and limited the GB migration, promoting the nucleation and inhibiting the growth of DRX grains. At 1100–1150 °C, B has little effect on the DRX due to sufficient energy supply by higher temperature. Under the above beneficial effects of B, the hot ductility of S32654 was improved to varying degrees at 850–1150 °C. However, as the temperature increased to 1200–1250 °C, B segregation decreased the solidus temperature and enhanced the liquefaction cracking tendency, resulting in a deterioration of the hot ductility. [ABSTRACT FROM AUTHOR]