Clad profiles in edge welding using a coaxial powder filler nozzle

The powder catchment and clad profile of the edge welding were investigated by experimental and numerical approaches in this study. The clad profile on the edges joined by a coaxial powder filler nozzle with a CO2 laser was measured and compared with the powder concentration mode, which was confirmed by powder flow visualization and numerical computations. In the numerical simulation of an impinging jet of gas-powder flow on an edge joint, the powder concentration distributed on a V groove joined by two plates was solved by FLUENT software. Based on the Gaussian mode of the powder distribution in the jet flow, a simplified mode function was proposed to estimate the clad profiles in the edge joint. Cladding experiments were performed for mild steel substrates with thicknesses of 2 and 6 mm under 1 kW CO2 laser irradiation for 304L stainless steel powder. The results show that the concave clad profiles were generated at large incline angles and the powder catchment efficiency might increase with the joint angle and substrate thickness. Based on the analytical results of the cold powder streams impinging on the edge joint, the similarity between the clad profile and the powder concentration in the edge joint is retained only at small incline angles for thin substrates. Due to the heating effects of laser beam spot and the powder re-distribution inside the edge joint, the deviation of the clad profile between the computation and experiment is increased with the incline angle and substrate thickness. (C) 2001 Elsevier Science Ltd. All rights reserved.