CHARACTERIZATION OF HARD CHROMIUM NITRIDE COATINGS DEPOSITED BY CATHODIC ARC VAPOR-DEPOSITION

Cr-N coatings, of various stoichiometries, were deposited on 304 stain less steel and M4 tool steel by planar cathodic are vapor deposition ( CAVD). This investigation concentrated on the effects of the CAVD proc ess parameters and the resulting mechanical properties. To achieve thi s, several properties of the deposited films were studied; hardness, a dhesion, coefficients of friction, residual stress, texture and stoich iometry. Hardness and adhesion were measured by low load Vicker's inde ntation and diamond scratch testing respectively. The adhesion exhibit ed an inverse relationship with respect to the hardness of the Cr-N co atings. Hardness values averaged 17.7 GPa while maximum adhesion value s of the Cr-N coatings exceeded 85 N using a 0.2 mm diamond stylus. Ty pical values for the coefficients of friction remained lower than 0.10 (diamond against Cr-N). Residual stress was measured by glancing inci dence X-ray diffraction (GIXRD). Residual stress measurements indicate d a transition from compressive to tensile stresses for midrange level s 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 .