Development of coating structure and adhesion during high velocity oxygen-fuel spraying of WC-Co powder on a copper substrate

This paper deals with the mathematical modeling of the development of the WC-Co coating structure and adhesion on a copper substrate during high velocity oxygen-fuel (HVOF) spraying. Two types of substrates are considered: smooth (polished) and rough (grit blasted), Variations of solidification time, solidification velocity, thermal gradient, and cooling velocity in the coating and substrate interfacial region are studied. Development of the amorphous and crystalline structures in the coating and of the crystalline structure in the substrate interfacial region is discussed. Behavior of the crystal size and intercrystalline distance with respect to the thermal spray parameters and morphology of the substrate surface is analyzed. Optimal conditions for the formation of fine and dense crystalline structure are determined. Structural changes in the solid state of the substrate occurring because of heating and rapid cooling are considered. Mechanical and thermal mechanisms of development of the substrate-coating adhesion are discussed, Results obtained agree well with experimental data.