Microstructures and Mechanical Properties of 12Cr12Mo Martensitic Stainless Steel Manufactured by Selective Laser Melting

In this study, 12Cr12Mo martensitic stainless steel was manufactured using selective laser melting (SLM). The resulting microstructures and mechanical properties were analyzed under optimal process parameters to understand the correlation between the process, microstructure, and properties. The results showed that only a single martensitic phase is present in the SLM samples, attributed to the exceptionally rapid solidification rate and high density of dislocations. It was observed that the 12Cr12Mo microstructure consists of interspersed columnar and equiaxed grains at the microscale, while fine body-centered cubic (bcc) lath martensite with high dislocation density is observed at the submicron scale. SLM-prepared 12Cr12Mo stainless steel exhibits impressive mechanical properties due to its hierarchical microstructure. Under optimal process parameters, the fabricated samples achieved a microhardness of 544.91 HV, with yield and ultimate tensile strengths of 729 ± 24 and 842 ± 19 MPa, respectively, but elongation is limited to 7 ± 0.6%. The cellular and martensitic structures with high dislocation density along grain boundaries are the mean factor for the increased strength but reduced ductility. Observations of a disintegrated surface and river-like patterns suggest a brittle fracture mode in 12Cr12Mo stainless steel prepared by SLM.