Powder particle–wall collision-based design of the discrete axial nozzle-exit shape in direct laser deposition

To improve the efficiency of direct laser deposition (DLD) metal powders, a concentrated powder-stream distribution is required, which can be affected by shape powder-delivery nozzle. In this study, simplified, powder particle–wall collision-based 3D numerical model flow in nozzle was used to simulate influences nozzle-exit on concentration stream distribution, characterized its diameter. The parametrized exit-cone angle, length, and inner-surface roughness. Based simulation results, shapes three angles (0°, 3.5° 7.2°), various lengths surface-roughness values were designed. For two larger particle sizes 22 ?m 82 considered, wall-collision-dominated regime influence experimentally confirmed. particular, significant decrease diameter when increasing divergent cone angle or decreasing surface roughness nonlinear length shown. Using single-layer, powder-deposition experiments it demonstrated that modifying design shape, powder-catchment increased 13% due 19% reduced