A Numerical Study of Powder Wetting Influence on the Morphology of Laser Powder Bed Fusion Manufactured Thin Walls

Abstract

Direct numerical simulation of laser powder bed fusion process on mesoscopic level can serve as a predictive tool for the construction quality of a part. The non-stationary fluid dynamics with surface tension and wetting effects, recoil pressure, heat transfer and powder deposition are included in the high-fidelity model formulated in the paper. The lattice Boltzmann method (LBM) is used for the simulation of the melt-pool dynamics and heat transfer while the heat equation is numerically solved on a large-scale adaptive grid. The discrete element method (DEM) is used for the simulation of powder deposition after each layer for the multilayer simulations.  A hypothesis is proposed that the powder wetting is a key parameter defining the morphology of a multilayer thin-wall detail. A number of numerical experiments of the thin wall builds of Inconel 625 is carried out in comparison with the experimental data of Air Force Research Laboratory (AFRL) Additive Manufacturing (AM) Challenge Series. The model accurately predicts the wall shape and height profile for all thin wall cases available in the AFRL AM Challenge data. It is shown by the simulations, that the wall height variation and height of the hill at the beginning of the track is strongly dependent on the wetting condition of the powder by the melt. An explanation to the effect is proposed based on melt pool dynamics in the presence of powder. It is concluded that the powder wetting is necessary to be taken into account for the predictive modeling of the morphology of mesoscopic thin-walled structures.

Keywords: Thin-walled Structures, Mesoscopic Lightweight Construction, Homologous Wetting, 3D Mesoscale Simulation, High-performance Computing