Influence of powder morphology on laser absorption behavior and printability of nanoparticle-coated 90W-Ni-Fe powder during laser powder bed fusion

In this work, mesoscopic simulation and experimental studies were applied to investigate the influence of powder morphology and characteristics on laser absorption behavior and printability of nanoparticle-coated 90W-Ni-Fe powder during laser powder bed fusion (LPBF). The mechanism of laser-material interaction and the thermal behavior of molten fluid during LPBF were revealed, thereby optimizing the powder preparation parameters. It showed that when the powder preparation parameters were optimized (i.e., ball-to-powder weight ratio of 1:2, milling speed of 250 rpm, and milling time of 6 h), the Ni and Fe nanoparticles were uniformly dispersed on W particles and, meanwhile, the sufficiently high sphericity of the W matrix particles was maintained. The nanoparticle-coated 90W-Ni-Fe powder had a sound laser absorption behavior with laser absorptivity of 93.51%, leading to the high LPBF printing quality with a smooth surface free of balling phenomenon and microcracks. Specimen fabricated using optimally prepared powder has a high density of 98% and a low surface roughness of 7.91 μm. The LPBF-processed 90W-Ni-Fe alloys had a uniform hardness distribution with an average value of 439.47 HV1 and significantly enhanced compression properties with compressive strength of 1255.35 MPa and an elongation of 24.74%. The results in this work provided a physical understanding of complex and interdependent laser-powder interaction and melt pool formation mechanisms during LPBF of W-based alloys that are governed by powder characteristics.