The effects of interstitial inert gas on the spreading of Inconel 718 in powder bed fusion

The effects of interstitial gas on the spreadability of Inconel 718 powder under conditions relevant to powder-bed fusion additive manufacturing (PBF-AM) are investigated through high-fidelity discrete element method-lattice-Boltzmann (DEM-LB) simulations. Here, a fine computational grid fully resolves the flow of inert gases around each grain. Furthermore, Inconel 718 powder is fully characterised, and the DEM contact models are calibrated via a rigorous procedure devised specifically for metallic powders in additive manufacturing. This procedure involves angle of repose and slide tests, nano-CT imaging, and shear cell experiments. The spreading behavior of Inconel 718 by a blade is then simulated in both vacuum and gaseous environments. The findings reveal that the presence of inert gases increase the amount of deposited powder and the bed thickness. As the blade speed increases, the disparity in powder deposition between gaseous and vacuum surroundings becomes more pronounced. Moreover, it is observed that the newly deposited particles are disrupted by the wake of the blade, given that the gas velocity near the bed can exceed the terminal velocities of most particle size classes in the simulation.