Numerical simulation and experimental investigation of the influence of process parameters on gas-powder flow in laser metal deposition

Abstract

Uniform, stable and highly converged powder feeding is crucial to guarantee the compact structure, uniform composition and smooth surface of parts in laser metal deposition. Numerical gas-powder flow model for four-stream nozzle was established on the basis of Euler-Lagrange theory. Employing the gas-powder flow model, flow distributions for TC4 and 304L metal powder feeding were obtained respectively in FLUENT. The consistency of simulation and experimental results proved the validity and reliability of the model. Accordingly, influence of powder flow rate, particle properties (particle size, density, sphericity) and other processing parameters on powder flow concentration was studied through numerical simulations and experiments. It was found that metal powder could be transported efficiently with a powder flow rate ranging from 2.5–3.5 kg/h and a carrier gas flow rate of 6 L/min. With the optimized parameters, powder utilization could be improved while the focal length was increased. With the increase of particle size and its shape factor, the concentration of powder flow was increased and focal point was raised. Metal particle sizes of 120 mesh and 100 mesh were found to be suitable for powder utilization. Dispersion of powder flow was controlled more obviously when the shape factor of the particle approached 1.0. And besides, focal position moved up and focal length became shorter with the increase of particle density. Employing the optimized powder flow process parameter for 304L powder with particle size of 75–150 µm, single-track cladding experiment was performed. This study was significant for matching processing parameters with high deposition rate and for further study on nozzle optimization design in laser metal deposition.