Effects of coating thickness and slip ratio on durability of thermally sprayed WC cermet coating in rolling/sliding contact

Using a two-roller testing machine, the authors examined the surface durability of thermally sprayed WC–Cr–Ni cermet coating in lubricated rolling or rolling with sliding contact conditions. The coating was formed onto the roller specimen made of an induction hardened carbon steel or a thermally refined carbon steel by high velocity oxy-fuel flame spraying (HVOF). In the experiments, the WC cermet coated roller was mated with the carburized steel roller without coating and a maximum Hertzian stress of PH=1.2 or 1.4 GPa was applied in line contact. First, it was recognized that the life-to-flaking has a tendency to increase as the thickness of coating increases. Secondly, it was shown that the occurrence of flaking depends on the rolling/sliding conditions. Finally, based on the results of elastic–plastic analysis of subsurface layer, the authors discussed the effects of the coating thickness and the slip ratio on the durability of coated roller.