Tribological and Corrosion Properties of Cr-Zr-N Coatings

In this work, ternary Cr-Zr-N coatings with not only much improved mechanical proeprties but also a very low surface roughness were synthesized by closed field unbalanced magnetron sputtering with vertical magnetron sourfaces and their tribological properties under the various relative humidity (RH) conditions were investigated. Especially, in the case of the Cr_1-xZr_xN coating with x=0.34, its friction coefficient obtained under a 90% RH environment was compared with that of DLC (diamond-like carbon) films measured under the same conditions. In addition, to evaluate the corrosion behavior of the coatings, we carried out potentiodynamic polarization tests in a deaerated 3.5 wt.% NaCl solution at 40oC and we compared the results with those obtained from CrN films. The tribological behaviors of the Cr-Zr-N coatings did not seem to be significantly affected by the humidity of the air. Under a 90% RH environment, the average friction coefficient of the Cr_1-xZr_xN coating with x=0.34 against a steel ball was approximately 0.17 and this value was lower than those of the CrN (0.49) and DLC (0.2) fims. In the potentiodynamic polarization test results, we found that the corrosion resistance of the Cr-Zr-N coatings was significantly improved in comparison with that of CrN and that their corrosion current density (icorr) and corrosion rate decreased with increasing Zr content (x value).