This article discusses the relation between hardness of substrate and WC-Co coating destruction by HVOF. This research uses the indentation test of a hard ball to study WC-Co coating destruction by HVOF thermal spray system. By adjusting the hardness of substrate, the article investigates and evaluates the effects on coating destruction. As for base material hardness, it is necessary to have beyond 500HV (49.1HRC) in order to keep surface hardness of sprayed coating. It was also observed that when sprayed coating received pressure, plastic deformation of the base material made the destruction more likely to occur. By measuring HRC surface hardness of sprayed coating and observing HRC indentation, the research concluded that strength evaluation of sprayed coating is possible.