Effect of Heat Treatment on Microstructure and Mechanical Properties of a Precipitation-Hardened Stainless Steel Prepared by Selective Laser Melting

In this paper, the effect of heat treatment on the microstructure and mechanical properties of SLMed corrax (CX) stainless steel was investigated. The results showed that solution treatment (ST) promoted the transformation of residual austenite to martensite, and the lath martensite structure was formed during solution treatment, with a preferred orientation of crystal face (111). Meanwhile, the solution treatment led to the obvious grain growth and dissolution of NiAl precipitates into the matrix, which weakened the mechanical performance of SLMed samples. Furthermore, the NiAl precipitates in nanoscale were formed again during the subsequent aging treatment (AT). At the aging temperature above 580 °C for 3 h, some martensite was transformed into the reversed austenite, resulting in the occurrence of overaging. The highest hardness and strength were obtained in the parameters of ST 900 °C/ 1 h + AT 530 °C/ 3 h. The maximum hardness, yield stress (YS) and ultimate tensile strength (UTS) reached 526.3 HV, 1486 MPa and 1598 MPa, respectively, all of which were improved by about 50