Performance Study and Heat Treatment Analysis of Selective Laser Melting SiC/18Ni300 Martensitic Mold Steel Composites

Abstract

To improve the mechanical properties of 18Ni300 mold steel, the composite material with 18Ni300 steel as the matrix and SiC as the reinforcement was prepared by selective laser melting (SLM) technology. The effects of the addition of different volume fractions of SiC powder and different heat treatments on the surface morphology, microstructure, and mechanical properties of the formed specimens were investigated. The results showed that with an increase in the SiC powder volume fraction from 0 to 1 vol.%, the uplift and spheroidization of the top surface of the specimens became serious, the relative density decreased, the roughness increased, and the grain growth pattern gradually resulted in the transformation of cytosine into columnar crystals, dendrites, and equiaxed dendrites. Further, the hardness and tensile strength first increased and then decreased with the gradual decrease in the elongation. At 0.5 vol.% SiC powder, the hardness and tensile strength of the specimens reached a maximum of 371.1 HV and 1.51 GPa, respectively, indicating an increase of 6.91 and 54.83% compared to the specimens without SiC powder. The solid solution combined with aging-treated specimens enhanced the hardness and tensile strength of the specimens without destroying the elongation of the specimens, the maximum hardness and tensile strength increased by 51.34 and 32.45%, respectively, and elongation increased by 3.85% compared with those without heat treatment, which is of great significance for the practical application of the SLM- formed SiC/18Ni300 alloy.