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

为了提高金属粉末直接激光沉积 (DLD) 的效率，需要集中的粉末流分布，这可能会受到粉末输送喷嘴形状的影响。在这项研究中，使用简化的、基于粉末颗粒-壁碰撞的喷嘴中粉末流动的 3D 数值模型来模拟喷嘴出口形状对粉末流分布浓度的影响，以直径为特征。喷嘴出口形状由出口锥角、长度和内表面粗糙度参数化。根据仿真结果，设计了三种出口锥角（0°、3.5°和7.2°）、不同长度和表面粗糙度值的喷嘴出口形状。 对于 22 μm 和 82两种较大的粒径 考虑到μm，实验证实了以壁碰撞为主的状态和喷嘴出口形状的影响。特别是，当增加发散的喷嘴出口锥角或降低其表面粗糙度和锥长度的非线性影响时，粉末流直径显着减小。使用单层粉末沉积实验证明，通过修改喷嘴出口形状的设计，粉末捕集效率由于喷嘴出口锥角的增加而提高了 13%，由于喷嘴出口锥角的增加而提高了 19%。降低表面粗糙度。