Mechanism research on accelerated embrittlement phenomenon of a warm-deformed Cr-Mn-Ni-Mo-N austenitic stainless steel

Effect of Ni, Mo content and warm deformation at 800 °C and 940 °C on Cr23C6 and Cr2N precipitation behavior and room temperature (RT) impact toughness of a Mo-contained high N austenitic stainless steel was researched in this study. Results showed that mass percentage of Mo and Ni should be adjusted for sufficient γ phase region. The real precipitation kinetic of Cr23C6, Cr2N and σ phase was affected by related elemental composition and deformation parameters. After the same aging, the embrittlement of warm-deformed specimen was accelerated due to obvious increase of intergranular Cr23C6 and discontinuous intragranular cellular Cr2N precipitates. The accelerated embrittlement and Cr23C6 and Cr2N precipitation were induced by high density dislocations generated during warm deformation. Dislocations dramatically increased adjacent precipitation nucleation opportunity and the growth rate of Cr23C6 and Cr2N during aging process within corresponding sensitive temperature interval. Dislocation density also strongly affected growth direction and thickness of Cr2N lamellae. Real forging parameters should be controlled to avoid this accelerated Cr23C6 and Cr2N precipitation.