High-fidelity numerical model of melt pool dynamics in selective multi-laser melting of Inconel 718 under different scanning strategies

Abstract

The application of multi-laser scanning technology to additive manufacturing is one of the important means to improve its printing efficiency of additive manufacturing. Therefore, it is of great significance to study the evolution law of overlap region between multi-laser melt pools under different scanning strategies. Based on the discrete element-computational fluid dynamics method, the dynamic evolution of melt pools in the selective multi-laser melting (SMLM) is studied at the particle scale when two lasers scan the powder bed in the opposite (DL_O) or the same (DL_S) directions. The influence of laser spacing in SMLM with DL_O scanning on the melt pool dynamic behavior of the overlap region for Inconel 718 is especially investigated. The result shows that, in the SMLM process with DL_O scanning, when the laser spacing is 2–3 times the laser beam radius of 27 µm, the melt pools in the overlap region completely merge without obvious boundary lines, resulting in good surface quality and higher density of the product, which is consistent with that in DL_S scanning. Although the disordered flow may result in poor texture of the part manufactured by SMLM with DL_O, it can promote the melt pools to merge sufficiently in the overlap area to reduce the risk of inter-track defects. The thermal-mechanical finite element method at process-level is also used to examine the distribution of temperature and stress fields during multi-layer multi-track dual-laser printing under these two scanning strategies. The stress distribution is found to be significantly different under the DL_O and DL_S scanning strategies, so the residual stress in SMLM can be reduced by ingeniously using these two scanning methods in different zones and layers. Therefore, this work provides a clue on how to optimize the SMLM process.