Numerical Simulation and Experimental Study of Powder Flow Distribution in High Power Direct Diode Laser Cladding Process

High power direct diode laser (HPDDL) offers a rectangular laser beam with top-flat intensity distribution making it an ideal tool for wide-clad deposition. In the HPDDL-based cladding process, the powder is commonly fed laterally through a wide nozzle into the molten pool by means of a carrier gas. In order to successfully utilize this cladding technique, the powder feeding behavior needs to be carefully controlled. In this study, based on an investigation of commercial powder feeding nozzles, a 3D computational fluid dynamics (CFD) based gas-powder flow model was developed. The effects of the nozzle exit geometry, powder properties (particle size, density and shape), and powder feeding parameters (powder feeding rate and carrier-gas flow rate) on the characteristics of the powder flow were studied. A high-speed CCD camera was used to capture the powder flow characteristics such as the particle velocity and particle distribution. Deposition experiments are also performed to verify the predicted powder catchment efficiency and to check the clad geometry.