Abstract

Cold spray is a technique to make a coating on a wide variety of mechanical or electric parts by spraying solid particles accelerated by a high-speed gas flow through a converging-diverging nozzle. Experimentally it is well known that the particles start to deposit on the substrate when the impact velocity exceeds material dependent threshold value. Therefore, the particle velocity at impact is very important in the cold spray. In order to investigate the gas flows in the nozzle, we measured the wall-static pressure of the part of diverging nozzle by using pressure sensors attached to the nozzle. Also, quasi-one-dimensional analysis of the gas flow in the cold spray nozzle was conducted for comparison. As a result, the wall-static pressure from nozzle throat to downstream flow decreases smoothly at all the stagnation pressures and increases from the front position of pseudo-shock wave. In addition, from the comparison of experimental and analytical results, it is clarified that the gas flow in the cold spray nozzle is turbulent and can be regarded as a quasi-one-dimensional flow.

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