A model for coated surface hardness

Abstract

The authors present a model that predicts the hardness of a film deposited on the surface of a substrate. The model is based on a simple mathematical relationship involving the hardness of the film and the hardness of the substrate, together with the hardness of the composite film/substrate at a given film thickness/penetration depth ratio. The parameters of the present model depend on the mechanical properties of the film/substrate pair and can be experimentally determined by using depth-sensing hardness instruments. In the models found in the literature, the equation parameters are constants typical for each model. The present model is proposed and validated for the case of a film (W-C-Co coating) harder than the substrate (various metallic materials) and it allows determination of the film hardness without the need to determine either the film thickness or the substrate hardness.