Powder flow simulation of a ring-type coaxial nozzle and cladding experiment in laser metal deposition

摘要

A 3D full size numerical model of a ring-type coaxial nozzle was established to obtain particle space trajectory and convergence character. The realizable k-epsilon model was applied in the gas flow phase. The powder flow was coupled with the gas flow by using Euler-Lagrange approach as a discrete phase model. Different powder material and particle sizes were selected to calculate the powder concentration distribution. The simulated powder stream morphology matched well with the experimental results of high-speed camera observations. Simulation results showed that using mean diameter (d) over bar to replace Rosin-Rammler distribution of particle size could get accurate flowing characteristic results. Simulation results also showed that this substitution could save computational resources and reduce the computing time significantly. The presence of the coaxial shielding gas has direct impact on the powder mass concentration spatial distribution, maximum value convergence height, and spot size of the powder flow. For 316L with small particle size and Ni60A with large particle size, we found different change regularities and no linear relationship was found. Therefore, it is recommended not to change the input volume of coaxial shielding gas without special needs. Simulation results, combining with the laser cladding experiments of Ni60A, have demonstrated that the developed ring-type coaxial nozzle could transport powder efficiently and form excellent deposited layers. The conditional powder utilization ratio can be as good as 75.9%.

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