High-precision laser powder bed fusion of 18Ni300 maraging steel and its SiC reinforcement composite materials

Abstract

Thanks to the need for refinement in the mold field, high-precision laser powder bed fusion (HP-LPBF) has become a critical technique for manufacturing new high-precision molds. The influence of HP-LPBF process parameters for densification of 18Ni300 maraging steel (MS18Ni300), as well as the related optical micrograph (OM), microstructure, phase composition, and mechanical properties of optimal relative density specimens, were comprehensively examined in this study. The sequence of HP-LPBF process parameters on the relative density of the specimens was investigated using the orthogonal experimental method. With a relative density of 99.18 ± 0.11 % and a surface roughness of 3.59 ± 0.32 μm, the optimal process parameters was attained. The influence of adding SiC on the specimens' OM, microstructure, phase composition, and mechanical properties were compared and studied. The results show that the building direction (BD) is the dominant heat flow direction in HP-LPBF by EBSD analysis and that the rotating 67° scanning strategy can effectively improve the isotropy of the mechanical properties of HP-LPBF parts. The MS18Ni300 specimen has a particularly thin cellular microstructures with a diameter of 6.11 μm. In addition, the dominant phase composition of the MS18Ni300 specimen was martensite (α). The microstructure of SiC (volume fraction of 1 %)/MS18Ni300 (M1) composites was significantly refined, and changes in the microstructure were primarily due to SiC's physical properties. The addition of SiC particles leads to a weakening of the preferred crystallographic orientation of the grains. The average grain size was 3.21 μm. No new phases were produced, but the mechanical properties were improved. The ultimate tensile strength and hardness of M1 were 1.33 GPa and 390.2 HV, respectively. The strengthening mechanism of SiC was discussed.