Mathematical simulation of the thermal processes occurring during the formation of a WC-Ni coating on a low alloy steel by high velocity oxy-fuel (HVOF) spraying was carried out. The factors assessed during the simulation include the overall temperature changes, the solidification of the coating, the melting and subsequent solidification of the interface regions of the substrate and the thermal interactions between the different layers of the coating.The optimum conditions for the formation of good structures in the coating and the adjacent substrate are estimated.