In the cold spray process, cross-sectional shape of the nozzle has a significant effect on spray pattern of coatings. There is a rectangular and a circular cross-sectional shapes on the cold spray nozzle. It has been reported that the rectangular nozzle provide a more uniform particle velocity across the exit of the nozzle. The circular exit nozzle is parabolic in shape. So spray pattern with the rectangular nozzle is wider than that with the circular spray nozzle. The goal of this investigation is to establish a design for the cold spray gun nozzle in order to gain more uniform spray profile of coatings. We have investigated the influence of expansion ratio, nozzle total length and the ratio of nozzle length of divergent section and parallel section of rectangular nozzle on behaviours of gas and particle by the computational fluid dynamics (CFD) in high pressure cold spraying. In this study, the spray pattern and microstructure of copper coatings with the rectangular cross-section nozzle optimized by CFD analysis in high-pressure cold spraying are reported. The optimized rectangular nozzle provide a more uniform spray profile of coatings. Relatively finer powder tended to deposit on the end of the coating.

The goal of this work is to establish a design for a cold spray nozzle that produces a flatter spray pattern. To that end, experiments and CFD calculations are carried out to investigate the influence of nozzle geometry and expansion ratio on the behavior of copper particles and gas flows during high-pressure cold spraying. It is found that there is an optimal ratio for the lengths of the diverging and parallel sections in a rectangular nozzle in regard to particle velocity and deposition efficiency. The results are also compared with circular nozzle designs.