Microstructure and Mechanical Responses of CX Stainless Steel Produced by Selective Laser Melting

In this study, a high-strength stainless steel (CX stainless steel) was prepared by selective laser melting (SLM), using solution aging to improve the microstructure and mechanical properties of the printed part. In its solution-aged state, CX stainless steel is composed of martensitic lath with high-density dislocations and numerous cellular substructures. Precipitation of NiAl with an average particle size of 12 nm, and occurrence of alumina inclusions with an average size of 70 nm were observed. Micro-hardness, yield strength, and the ultimate tensile strength (UTS) of the SLM CX stainless steel were up to 520HV0.2, 1602 MPa, and 1674 MPa, respectively. This significant improvement in yield strength can be attributed to high-density dislocation entanglement, followed by a second-phase strengthening effect. Elongation and impact toughness of the SLM CX stainless steel were 8.9% and 12.3 J, respectively. The fracture morphology of the tensile and impact fracture surfaces is slightly different – mainly in cleavage plane and dimple size – but, in general, the primary fracture mechanism can be classified as quasi-cleavage fracture.