Influence of Microdefect on Mechanical Behaviors of CX Stainless Steel Produced by Selective Laser Melting

In this study, a high-strength maraging stainless steel (CX stainless steel) was prepared using selective laser melting (SLM) technology. Solution aging was employed to enhance the microstructure and mechanical properties of the printed part. The heterogeneous microstructures of CX steel were studied, which mainly consisted of martensitic laths with high-density dislocations and numerous cellular substructures. Precipitation of NiAl with an average particle size of 12 nm and the occurrence of alumina inclusions with an average size of about 70 nm were observed. A high ultimate tensile strength of 1647 MPa, micro-hardness of 520 HV_0.2 and a good elongation of 8.9% was achieved for CX stainless steel. Moreover, the strengthening mechanism and crack propagation law are analyzed from the perspective of microdefects, such as fine grains, high density dislocations, cellular structure, nano-precipitates and inclusions.