This work involves modeling of cold spray process in order to predict gas flow as well as particle conditions upon impacting on a substrate. Particle normal velocity is found to be the most important factor to improve the deposition efficiency and coating quality. Particle velocity is influenced by the substrate geometry and location. The shape and strength of the bow shock near the substrate of different geometries (such as concave, convex, and flat) are studied, and particle normal velocities impacting on the substrates located at various stand-off distances are calculated. Furthermore, the numerical simulation is repeated with particles of various sizes and different feeding gas (Helium and Nitrogen). The results are compared to obtain the optimum substrate location and the appropriate particle size for each feeding gas.