Influences of three-route gas flows on powder converging behavior in coaxial powder feeding nozzles

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.