Revealing melt-vapor-powder interaction towards laser powder bed fusion process via DEM-CFD coupled model

Abstract

Abstract During the laser powder bed fusion (LPBF) process, powder spattering is a crucial phenomenon to consider. This primarily arises from the intense interaction between the laser and the material. The ensuing metal vapor, induced by the evaporation process, plays a pivotal role in instigating powder spatter, which significantly impacts the quality of the resultant part. One of the pressing challenges in the field is the capture and quantitative investigation of the interplay between the melt, vapor, and powder. Such lack of clarity impedes our path to achieving defect-minimized LPBF production. In this study, we propose a physics-based model that elucidates the integrated interaction of vapor, melt, and powder using a coupled DEM-CFD approach. Our findings indicate that the vapor flow undergoes four distinct states: initialization, continuation, transition, and interruption. These states correlate closely with the progression of vapor-induced depressions and powder spattering. As compared to the existing experimental data, our model provides a more precise and comprehensive understanding of vapor flow states and their associated velocity magnitudes. Furthermore, we identify three distinct patterns of powder spatter: inward, upward, and outward flows, where powder inward flow is mainly caused by shielding gas, while the upward and outward patterns are induced by metal vapor.