The High Velocity Oxygen Fuel Process (HVOF) involves strong interactions between gas and coating particles. There are two kinds of shocks observed in an HVOF process; shock diamonds near the nozzle exit and bow-shocks on the substrate. These shocks are responsible for deviation of particles from their trajectories, which reduce the chance of some particles landing on the substrate. An attempt is made to study the behavior of particle trajectory as it interacts with the bow shock on the substrate. The strength and location of bow shock was found to be strongly dependent on the substrate geometry and stand-off distance. In this work, particles of varying sizes, impinging on the substrate with various substrate stand-off distances and configurations (Flat, Concave and Convex) are simulated. Consequently, the effect of shock diamonds and bow-shock, on particle trajectory is studied.