UNS S32707 hyper-duplex stainless steel processed by powder injection molding and supersolidus liquid-phase sintering in nitrogen sintering atmosphere

Abstract

UNS S32707 hyper-duplex stainless steel (HDSS) was prepared by powder injection molding (PIM) and supersolidus liquid-phase sintering from powder prepared by a plasma rotating-electrode process, and the nitrogen content and relative density of the sintered parts were 0.37% and 97.9%, respectively. The densification and nitrogen content of sintered parts at different sintering temperatures in a nitrogen atmosphere were studied. The results indicate that the relative density increased gradually, whereas the nitrogen content of the sintered parts decreased gradually with increasing sintering temperature under the nitrogen pressure of 0.2 bar. The parts sintered at 1400 °C for 1.5 h exhibited ideal sintering relative density and nitrogen content. After solution treatment at 1150 °C for 1 h, the ratio of ferrite to austenite was approximately 46.8:51.8; the measured tensile strength, the yield strength, the elongation and the hardness were 761 MPa, 529 MPa, 14%, and 321.4 HV, respectively. The samples prepared by PIM can achieve full densification followed by hot isostatic pressing and solution treatment, and its tensile strength and elongation are significantly improved, which is better than that of casting. This study provides a new method for the preparation of high-nitrogen-content HDSS with a complex shape and controllable nitrogen content by near-net shaping.