Catalysis effect of metal doping on wear properties of diamond-like carbon films deposited by a cathodic-arc activated deposition process

Abstract

Diamond-like carbon (DLC) films containing various metal dopings were synthesized by using a cathodic-arc activated deposition process. Metal plasma with intensive ion energies catalyzes the decomposition of hydrocarbon gases (C 2H 2), and induces the formation of hydrogenated DLC films with a mixture of sp 2 and sp 3 carbon bonds. The composite film structure consists of a metal-doped DLC film on top of a graded metal nitride interlayer, which provides enhanced mechanical and tribological properties. The catalysis effect of three common transition metal plasmas, including Cr, Ti, and Zr was investigated. This experiment depicts the advantage of the catalysis effect of Cr plasma in synthesizing DLC films with a higher sp 3 carbon bond ratio comparing with that of Ti and Zr plasma. The wear properties were correlated with the metal doping. The optimized Cr-C:H films with Cr and CrN interlayers give satisfactory wear performance in a ball-on-disk test with a lower wear rate of 2×10 −17 m 3/Nm and a lower friction coefficient of 0.1 sliding against WC counterparts. Wear life of Cr plasma activated DLC (Cr-C:H) outperforms that of Ti and Zr by nine- and twofold, respectively. The Cr-C:H film exhibits a dense microstructure and a higher sp 3 bond ratio, showing great potential for wear applications.