The effects of interstitial inert gas on the spreading of Inconel 718 in powder bed fusion
Sorush Khajepor, Omid Ejtehadi, Sina Haeri
Abstract
The effects of interstitial gas on the spreadability of Inconel 718 powder in conditions relevant to powder-bed fusion additive manufacturing (PBF-AM) is investigated through high-fidelity discrete element method–lattice-Boltzmann (DEM-LB) simulations, where a fine computational grid fully-resolves the flow of inert gas around each grain. Furthermore, Inconel 718 is characterised and the DEM contact models are fully calibrated through a rigorous procedure devised specifically for metallic powders in AM and involves angle of repose and slide tests, nano-CT imaging, and shear cell experiments. The spreading of Inconel 718 by a blade is simulated in vacuum and gas. It is found that the presence of the gas increases the amount of deposited powder and the thickness of the bed. As the blade speed increases, the difference in the powder deposition between gas and vacuum surroundings increases. Furthermore, it is observed that the newly laid particles are disturbed by the wake of the blade since the gas velocity near the bed can be more than the terminal velocities of most particle size classes in the simulation.