Particle-scale Simulation of Powder Spreading in the Presence of Gas in Additive Manufacturing

Powder bed fusion (PBF) is a versatile AM technology for rapidly creating intricate parts. A blade or roller spreads a thin layer of powder on a bed. A laser beam
fuses a cross-section of the part on the layer. Layer over layer, the process is repeated until the final part is produced. The spreading parameters can lead to higher bed roughness and porosity that degrade the quality of the final product. There have been studies on the effect of inert gas-particle interactions during the spreading process using CFD-DEM. However, the goal that differentiates this work from others is that we accomplish this task at a particle scale. We study the dynamics of the inert gas around particles and spreaders where each particle is fully resolved by many fluid cells. The powder is Inconel 718 which is characterised in the lab using SEM, Nano-Tomography and angle of repose tests. The drag force on particles is compared with contact forces. We show that the existence of gas can heavily affect bed solid fraction and surface roughness for low cohesive powder. The gas effect on high cohesive powder is less apparent, but the distribution of void spaces on the bed is noteworthy.