Mesoscopic simulation of surface morphology and thermodynamic mechanism during laser powder-bed fusing Ni-based composite: Underlying role of WC weight fraction

Abstract

This study demonstrates the significant effect of the interfacial heat and mass transfer during laser powder-bed fusion (LPBF) of WC/Inconel 718 composite due to its different laser absorptivity. A transient three-dimensional mesoscopic model was developed to simulate the thermal fluid flow and resulting surface evolution of a set of laser-scanned surface with different WC weight fraction during LPBF were studied using both numerical and experimental approaches. The thermal fluid flow model predicts that the interfacial heat and mass transfer is enhanced with increased WC weight fraction below 20 wt%. The more heated liquid with a reduced viscosity is understood to produce an adequate spreading of liquid and to favor the sufficient migration of WC particles, thereby contributing to a lower surface roughness. Using a further elevated WC weight fraction has a high tendency to result in an excessive heat and mass transfer of high-temperature WC particles /molten liquid, in turn disturbing the melt flow and causing the hindering migration of WC particles within pool. This can lead to an insufficient spreading of liquid and migration of WC particles, indicating a severely weakened surface roughness. The results are validated against the experiments and the underlying evolution mechanism of surface quality during LPBF of WC/Inconel 718 composite is further discussed. The meso-scaled modeling methodology considering the interfacial thermodynamics of WC /liquid provides a good predictive capability for the laser-powder-reinforcements interaction behavior, porosity development, and surface evolution.