Modeling of Substrate-Coating Thermal Interaction During High Velocity Oxy-Fuel (HVOF) Spraying of WC-Ni Powder

Abstract

The mathematical simulation of thermal processes occurring during the formation of a WC-Ni coating on a low alloy steel by HVOF spraying has been carried out. The factors assessed during the simulation include 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 different layers of the coating The mathematical simulation of parameters which could influence the structural characteristics of the coating and the interfacial region of the substrate has also been undertaken. The variations in the solidification velocity, the thermal gradients and the cooling velocity in the first layer of the coating have been determined. Similar parameters have been determined for the substrate but in this case attention has also been given to the melting velocity. The influence of these parameters on the formation of amorphous and noncrystalline structure in the coating is discussed together with the development of fine crystalline structures in the interfacial region of the substrate. The results obtained agree well with those obtained by direct metallographic examination of the coating and the substrate interfacial regions The optimum conditions for the formation of good structures in the coating and the adjacent substrate are estimated.