Design of laser-powder coupling for high-speed laser direct energy deposition

High-speed laser direct energy deposition (DED-LB) is developed to enhance deposition efficiency while maintaining build quality, compared to conventional DED-LB. The core of designing high-speed DED-LB involves formulating the laser-powder coupling, through optimizing nozzle structural and deposition process parameters. This study developed an analytical model to delineate the coupling mechanisms between laser beam and discontinuous coaxial powder stream (DCPS) comprised of individual single powder streams (SPSs). A data pretreatment method, involving gray processing, normalization, and renormalization of the thermal images successively, was applied to validate the model. Simulation results indicate that the DCPS spot size and SPS particle temperature distribution are predominantly influenced, respectively, by the nozzle structural and deposition process parameters. Through jointly designing the nozzle structural and deposition process parameters, a high deposition rate of high-speed DED-LB, which is 1.7 times that of conventional DED-LB, was achieved. This paper pioneers a new design methodology for high-speed DED-LB.