3D analysis of gas flow behavior and particle acceleration characteristics in cold spray additive manufacturing based on non-axisymmetric numerical models

Cold spraying has been recognized as a promising additive manufacturing technology due to its inherent characteristics of solid-state and high deposition rate. However, the nozzle clogging significantly limits the preparation of massive deposits. Therefore, in this work, a three-dimensional numerical model dedicated to nonaxisymmetric powder carrier gas and main working gas was established which accommodates the effects of pre-chamber length (Cl), the length difference between pre-chamber and powder injector (Pl), and the inner diameter of powder injector (Di1), implementing greater insights into the gas flow and particle acceleration behaviors. The numerical simulation results indicated that the gas vortex distribution and particle accelerating behaviors were highly related to Pl and Di1, and exhibited scarce correlation with Cl. The phenomenon of particle backflow caused by the gas vortex generated near the powder injector significantly augmented the probability of particles colliding with the nozzle sidewalls, thus elevating the risk of nozzle clogging. The negative influence of gas vortex on particles can be extremely minimized by the adoption of small Pl (e.g., 10 mm). The cold spraying experiments evidenced the numerical simulations. The adoption of Cl = 190 mm, Di1 = 1 mm, and Pl = 10 mm experienced no nozzle clogging within 9 min of spraying. The formation of small object featured by unconsolidated at the end of the powder injector validated the phenomenon of particle backflow observed from simulation. This work provided novel insights to alleviate nozzle clogging and facilitated one more step toward the industrialization of cold spray additive manufacturing.