High Velocity Oxygen Fuel Process (HVOF) is a thermal spray process which involves a supersonic, two phase flow of gas-particles. For practical feed rates the particle volume fraction is rather high and there is a strong interaction between the gas and the particulate phase. Overall and local particle loadings are important factors that affect the flow field in dense particulate flows. In this work we numerically model the two-phase flow of gas-particles by using a two-way coupling between the two phases through consideration of volume fraction of the particulate phase. It is observed that the presence of particles near the nozzle centerline can change supersonic flow to subsonic flow both inside and outside the nozzle. In addition, shocks and expansion waves are found to be significantly altered both inside and outside the nozzle, compared to the single phase gas flow without particles, where the flow is perfectly over expanded and shocks occurring outside the nozzle.