Characterization of hard chromium nitride coatings deposited by cathodic arc vapor deposition

Cr-N coatings, of various stoichiometries, were deposited on 304 stainless steel and M4 tool steel by planar cathodic are vapor deposition (CAVD). This investigation concentrated on the effects of the CAVD process parameters and the resulting mechanical properties. To achieve this, several properties of the deposited films were studied; hardness, adhesion, coefficients of friction, residual stress, texture and stoichiometry. Hardness and adhesion were measured by low load Vicker's indentation and diamond scratch testing respectively. The adhesion exhibited an inverse relationship with respect to the hardness of the Cr-N coatings. Hardness values averaged 17.7 GPa while maximum adhesion values of the Cr-N coatings exceeded 85 N using a 0.2 mm diamond stylus. Typical values for the coefficients of friction remained lower than 0.10 (diamond against Cr-N). Residual stress was measured by glancing incidence X-ray diffraction (GIXRD). Residual stress measurements indicated a transition from compressive to tensile stresses for midrange levels of both nitrogen partial pressure (e.g., 3.33 Pa) and substrate bias (e.g., -150 V). The stoichiometry of the films (N:Cr) ranged from 0.7 to 1 for nitrogen partial pressures of 2.00 and 5.32 Pa, respectively.