Defects caused by powder spattering and entrainment in laser powder bed fusion process: High-fidelity modeling of gas, melt pool and powder dynamics

Inconsistent product quality is one of the major bottlenecks hindering the widespread adoption of laser powder bed fusion (LPBF) additive manufacturing technology in various industries. A vital source of the inconsistency is the defect caused by the powder spattering and entrainment in the melting process. However, the mechanisms of defect formation remain elusive due to the highly-dynamic nature of multiphase flow. Here we develop a multi-physics simulation model, together with experiment validations, to simultaneously elucidate the gas, melt pool and particle dynamics in the melting process. The high-fidelity simulations successfully uncover the mechanisms of defect formation. In particular, the large agglomeration induced by the hot spatter coalescence can probably induce lack-of-fusion and porosity defects. The powder entrainment can probably cause particle inclusion defects in multi-material LPBF. Moreover, the momentum of entrained particles can alter the flow field at the melt pool tail. Under the guidance of simulation, we propose the criterion of defect generation in the melting process, which is beneficial to the real-time detection and mitigation of defects. The deep insights into the defects caused by powder spattering and entrainment provide valuable guidance for improving the consistency of LPBF parts.