Microstructure and Mechanical Properties of Metal Injection Molding HK30 Stainless Steel Sintered in N2 and Ar Atmosphere

The effects of different sintering atmospheres (nitrogen and argon) on the densification, microstructure, and mechanical properties of HK30 stainless steel were studied. Compared with those of the samples sintered in Ar, sintered samples in N2 had a lower density and higher N content. Some of the N atoms dissolved into the austenite matrix, and others were combined with metal atoms to be precipitated along the grain boundaries. Samples sintered in N2 had a higher hardness than those in Ar. The hardness decreased with the distance from the edge to the center. The highest hardness was 360 HV1.0 at the edge, the lowest one was 220 HV1.0 at the center. The samples sintered in N2 had a higher tensile strength than those sintered in Ar at testing temperatures from room temperature to 1000 °C.