Evaluation of adhesive behaviors of chromium nitride coating films produced by arc ion plating method

Abstract

Scrath tests and pin-on-disk wear tests were performed to clarify the cracking and delaminating behavior of CrN coatings. The CrN films were coated onto an aluminum alloy substrate, JIS A2024, by an arc ion plating method. Eight types of single-layered coating and multilayered coatings were prepared by changing the bias voltage during the deposition. LCI and LCII values were not improved by increasing the number of layers. The critical loads of the single-layered coatings decreased with increasing the bias voltage. It appears that, for the multilayered coatings, the combination of bias voltages influenced the critical loads. The critical loads strongly depended on dynamic hardness and Young's modulus. In particular, the critical loads of the multilayered coatings were influenced by the properties of the intermediate and bottom layers as well as the surface roughness, hardness and Young's modulus of the top layer. The large film delamination for single-layered coatings deposited using a high bias voltage occurred during pin-on-disk wear tests even though the critical loads of the single-layered coatings were higher than those of the multilayered coatings. If the brittle top layer could be broken and delaminated by the sliding contact, the ductile bottom layer coated under a bias voltage of 0 V could endure the complete delamination of film.