Mechanical properties of arc-evaporated CrN coatings. Part II: intrinsic film hardness and composite hardness

A systematic experimental investigation of the composite hardness of CrN coatings with different thickness on metal substrates with different hardness was carried out. The hardness response of the samples was studied over a range of applied loads between 100 and 2000 gf in Vickers tests. The measured hardness was analyzed as the function of the film thickness, the indentation size, and the substrate hardness based on the composite hardness models derived from the volume fraction law. The intrinsic hardness of CrN films, which was separate from the measured composite hardness, was independent of the coating thickness and given as a function of the indentation diagonal length. The '1/10th rule', which is considered the critical ratio of indentation depth to film thickness to evaluate the film hardness of coating systems has been analyzed from the plastic deformation theory for indentation, and it was analytically expressed by the functions of hardness and elastic modulus. (C) 2001 Elsevier Science B.V. All rights reserved.