Numerical study using nano-particles by varying the expansion ratio and height of cold spray nozzle to predict deposition efficiency

The coatings of zinc and its alloys are broadly used to prevent the rusting of substrate surfaces such as steel. Cold gas dynamic spray (CGDS) is an innovative coating technique in which the deposition of solid powder particles depends upon the kinetic energy of the particles rather than thermal energy. Therefore, application of cold spray is to provide superior rust resistance by depositing more materials, formation of passivation layer, and cathodic protection. In this study, numerical investigations on zinc nano size particles in CGDS were carried out. The height of the injector, the expansion ratio and the diameter of the inlet of the de-Laval nozzle was varied systematically by optimizing the stand-off distance using the two-dimensional axisymmetric models of CGDS, to study their effects on the velocity and the distribution of the particles. Prediction of the deposition efficiency was carried out using the various critical and erosion velocity models.