Numerical analysis of non-spherical particle effect on molten pool dynamics in laser-powder bed fusion additive manufacturing
In laser-powder bed fusion (L-PBF) additive manufacturing, the powder particles commonly produced by gas atomization have some non-sphericities. It is known that non-spherical particles affect the particle packing process, however, there is a limited understanding of their effect on molten pool dynamics resulted from laser-powder interaction. In this paper, the non-sphericities in L-PBF were studied by extending an existing computational framework which consisted of a particle packing model based on discrete element method (DEM) and a meso-scale molten pool model based on heat transfer and free surface flow. Experimentally, by visually inspecting the scanning electron microscope images of Inconel® alloy 718 powder particles, the non-spherical particle shapes were classified into two main types: particles with satellite and joined particles. These measured non-sphericities were simulated using a multi-sphere approach in DEM to generate the packed powder structure on a flat substrate, which was imported into the heat transfer and free surface flow model to calculate the molten pool dynamics. The calculated melt track dimensions were validated against the respective experimental data for single track melting. The effect of non-spherical particles on packing density, molten pool dynamics and melt track dimensions was discussed by comparing the simulated results for real powder with those for idealized powder consisting of spherical particles only.
Keywords: Laser-powder bed fusion, Non-spherical particle, Molten pool model, Multi-sphere approach, Nickel base superalloy