Numerical Simulation and Experimental Investigation of Gas-Powder Flow in Inner Powder Delivery System

The powder concentration distribution is a key factor which affects the powder catchment efficiency, laser attenuation and, consequently, the molten pool morphology in laser cladding. A cladding technique (via a hollow laser beam with a central powder delivery system), called inner powder feeding, is presented, which can greatly increase the powder utilization. According to the structure of laser head used for inner powder feeding, a three-dimensional numerical model is developed to simulate the gas-powder flow. The influences of the carrier gas flow rate, the shielding gas flow rate, and the geometry of the gas nozzle on powder concentration distribution are investigated. An observation system is developed to capture a particle distribution image. The gray values of the particle images show that their distributions coincide with the numerical results. The model also predicts the powder catchment efficiency. Single track deposition experiments are performed and the results are compared with a four-nozzle coaxial powder feeding system.