Melt pool dynamics and pores formation in multi-track studies in laser powder bed fusion process

In this work, the multi-physics of interactions between scanning tracks in laser powder bed fusion (LPBF) is investigated numerically by a CFD-based model. The results show that the flow at the head of the first track changes gradually which is driven by the intense centrifugal motion of the second track, and the combined tracks spread around. The voids between adjacent tracks are compressed by the molten liquid and sealed by the re-solidified part, finally leading to the large pores for the medium laser power and hatch space. The liquid phase overlap of the unidirectional track is narrower than the bidirectional scanning. The flow direction of the molten liquid changes several times and pores tend be eliminated under the island scanning strategy. The present study enhances the further understanding of physics in the LPBF process.