Analytical correlation of hardness and scratch adhesion for hard films

An analytical expression has been derived in order to correlate the critical load of scratch adhesion Lc with hardness and film thickness for thin hard films on softer substrates, based on the model proposed by Burnett, Rickerby and co-workers (B–R model) for interpretation of composite hardness measurements. The equation was used to calculate the correlation of Lc with Hv(sub) (substrate Vickers hardness), Hv(comp) (composite Vickers hardness), and t (film thickness) for AISI 316 stainless steel, HSS M2 and WC substrates coated with TiN films of different thickness. The calculated results were compared with experimental data for TiN films produced under similar conditions by PACVD and PAPVD deposition techniques. The present analysis yields quantitative results which agree to a satisfactory degree with experimental data in all cases considered and contribute to the understanding of the physical processes which control the deformation of the film–substrate mechanical system under scratch indentation conditions.