Mechanical properties of arc-evaporated CrN coatings: Part I — nanoindentation hardness and elastic modulus

CrN films with different thickness on high-speed steels were prepared varying the deposition time at constant condition of applied bias voltage of −300 V, cathode arc-current of 90 A in nitrogen with partial pressure of 5 Pa in an arc ion plating apparatus. The obtained coatings show single phase CrN with the preferential crystallographic orientation (220) and it indicates high compressive stress of 5.5 GPa. The depth sensing indentation data of CrN coatings tested with a Berkovich indenter have been analyzed for determining hardness and elastic modulus. Measured hardness was influenced by the substrate hardness when the ratio of indentation depth to the film thickness exceeded to 0.18. The intrinsic hardness of CrN films decreased with increasing indentation depth. The elastic modulus of the CrN coating, which was determined by the unloading curve, was found to be 375 GPa.