Heat Treatment Optimization of Laser Powder Bed Fusion Formed WC/18Ni300 Maraging Steel Composites

The 15% WC particle reinforced maraging steel 300 composites were fabricated by laser powder bed fusion. The effects of solid solution temperature, solid solution time, and aging temperature on the mechanical properties and morphology of the composite were then investigated using the response surface approach. The results show that the three heat treatment parameters have an interaction effect on yield strength and Rockwell hardness. The optimum heat treatment parameters obtained using the response surface method are solid solution at 846°C for 51 min and aging at 388°C for 300 min. After heat treatment, the melt pool of the sample formed by laser powder bed fusion disappears. The morphology is inhomogeneous cellular crystals and dendritic crystals before heat treatment. After the optimal and the worst heat treatments, the microstructure transforms into lath and acicular martensite, and its uniformity is remarkably improved. The heat treatment prompts mutual dissolution and diffusion between the WC reinforcing particles and the maraging steel 300 composites. The precipitated phases are dispersed along the grain boundary, and the thickness of the diffusion layer increases. After optical heat treatment, the composites' yield strength and Rockwell hardness increase by 129.4% and 52.3%, respectively.