Research Specifications

Cold spraying is a novel solid powder deposition method that utilizes powder kinetic energy for layer formation. In this process, spherical metal powders, typically in micrometer sizes, accelerate through a convergent–divergent nozzle to reach the necessary velocity, which is called the critical velocity for deposition. There is a large research gap regarding the effect of nozzle geometry on particle acceleration deposition efficiency. This study utilized computational fluid dynamics (CFD) and the Euler–Lagrange approach to investigate how the nozzle geometry affects the performance of the cold spray process to fill this gap. This study is novel in that it explores an optimized nozzle design to enhance particle velocity and deposition. Three convergent–divergent nozzles with different expansion ratios were selected, and simulations were conducted at various inlet pressures. The results showed that a lower expansion ratio caused the normal shock wave to move toward the nozzle outlet with the same inlet pressure for the nozzle. In addition, the results indicate that increasing the length of the divergent section to a certain extent led to an increase in particle velocity; however, further lengthening decreased the gas phase density and reduced the particle drag force. Particles with diameters less than 5 µm experienced a velocity decrease at the nozzle outlet owing to their low mass, low inertia, and deviation from the nozzle centerline caused by the bow shock on the substrate. A barrel section was designed to address this issue, which reduced the velocity loss in smaller-diameter particles by approximately 10% by optimizing the particle behavior and nozzle dimensions.