In the laser direct metal manufacturing process with coaxial powder feeding, when the powder was injected to the molten pool in the substrate,some of the metal powders would rebound. The rebound powders would clog nozzles and the dusts would pollute the laser lens. As a result, a mid-route gas was introduced. When the three-route gas (the mid-route gas, the carrier gas and the outer shielding gas) was simultaneously injected under hindered jet condition, by using the discrete phase model of FLUENT software, the influences of each gas on powder convergence were studied respectively to determine the range of each gas flow rate. Then the optimal mix relationship of the three-route gas was simulated using orthogonal method in order to guide experiments. The influences on powder convergence of three-route gas were verified through indirect methods. The results show that:experimental results are consistent with the simulation ones.

laser direct metal manufacturing, coaxial powder feeding, numerical simulation, three-route gas flow

在同轴送粉激光金属直接制造过程中，为防止反弹的金属粉末堵塞喷嘴和烟尘污染透镜，在激光腔内引入轴向保护气流并确定保护气流量的大小。采用FLUENT软件模拟中路气、载粉气、外层保护气对粉末汇聚特性的影响规律，并找出各自的取值范围。依据正交试验的方法，找出一组三路气体参数的最佳搭配关系，并通过间接方法验证了不同气路对汇聚浓度的影响规律。实验结果与模拟结果趋势基本一致。

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激光金属直接制造, 同轴送粉, 数值模拟, 三路送气

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