Relationship between hardness and optical properties of diamond-like carbon coatings

Correlation between hardness and optical properties of diamond-like carbon (DLC) coatings is considered. Various methods for the characterization of mechanical, chemical and optical properties of DLC coatings are used; however, some of these methods are destructive, and others are non-destructive. It was found that optical properties of DLC coatings are proportional to their hardness. The mathematical expression that allows to calculate the hardness of a DLC coating according to its refractive index is proposed. Therefore, it is possible to avoid the use of destructive methods (such as nano-indentation technique) to characterize DLC coatings.