Parameter optimization of the high-power laser powder bed fusion process for H13 tool steel

In this study, process parameter optimization was performed for the powder bed fusion of H13 tool steel under low- (400 W) and high-power (1000 W) conditions using the SLM 280HL machine. The effects of process parameters such as the laser power, scan speed, and hatching pitch on the density and microstructure of the as-built H13 tool steel were investigated. The specimen density was found to be slightly lower under the high-power condition than that under the low-power condition. Electron backscattering diffraction analysis identified that the as-built specimens showed a prolonged columnar microstructure in the build direction under the low-power condition. In contrast, for the specimens fabricated using the hull-core method under the high-power condition, the hull and core parts showed prolonged columnar and equiaxed microstructures, respectively. Phase distribution images indicated that the microstructures of the as-built specimens under the low- and high-power conditions contained martensite (bcc) and austenite (fcc) with a grain size of approximately 1 μm. Thus, it was found that the specimen density achieved using the 400-W laser is higher than that achieved using the 1000-W laser; moreover, the microstructure of the as-built specimen using the 400-W laser is different from that using the 1000-W laser.