Comparative Investigation and Characterization of the Scratch and Wear Resistance Behavior of TiN, CrN, AlTiN and AlCrN Cathodic Arc PVD Coatings

The scratch resistance and wear behavior at relatively high normal loads of binary (TiN, CrN) and ternary (Al_0.50Ti_0.50N, Al_0.68Cr_0.32N) coatings were comparatively investigated. Scratch test results showed that based on the adhesive strength the coatings can be ranked thus: CrN > TiN > Al_0.68Cr_0.32N > Al_0.50Ti_0.50N. The binary coatings were found to possess superior adhesion strength mainly exhibiting a tensile cracking failure mechanism. In contrast, the ternary coatings failed more severely by through-thickness cracking with spallation. The ternary coatings exhibited an average of 68, 67 and 55% improvement in the wear resistance at 15, 20 and 25 N normal loads, respectively, over the binary coatings. Abrasive and oxidation wear were the main wear mechanisms of the binary coatings. The formation of protective tribo-oxide layers is associated with the improved wear resistance behavior of the ternary coatings. High surface roughness due to large amount of surface defects coupled with low plastic deformation resistance and high Al content are reasons for low wear resistance of Al_0.68Cr_0.32N in comparison with Al_0.50Ti_0.50N coating.