Study of optimization features of gas-powder jets created by a coaxial nozzle with divided powder supply during direct laser deposition of materials

A comparative analysis of the dynamics of gas-dispersed flows created by a coaxial nozzle (with divided powder supply) used in laser cladding in the additive manufacturing of metal products and 3D printing has been carried out. A new analytical method for calculating the optimization of the coaxial nozzle geometry to improve the focusing of converging single jet powder flows is proposed. Numerical modeling showed that, being repeatedly reflected from the walls of the transport channel, powder particles can fly out with a wide range of angles of deviation of trajectories from its axis. It has been revealed that one of the main reasons for poor particle focusing is an increase in the transverse component of the particle velocity relative to the tube axis, while a decrease in the transverse component of the particle velocity stabilizes the powder jet, reducing the maximum divergence angle of the trajectories. For the first time, it has been experimentally shown that polishing the internal channel of copper tubes or using smooth quartz glass tubes significantly improves the transport properties and focusing of powder jets, providing a significant reduction in the particle scattering angle. The results of optical diagnostics and visualization using a high-speed camera are consistent with the data of numerical modeling. Recommendations are formulated to improve the efficiency of using a coaxial nozzle with divided powder supply in laser gas-powder cladding.