Microstructure, mechanical and tribological properties of WC/a-C:H coatings deposited by cathodic arc ion-plating

Abstract

Nanocomposite WC/a-C:H coatings were deposited in a cathodic arc ion-plating system, in which a WC target in Ar + C2H2 atmosphere and a variable acetylene flow of 0–200 sccm were used. The synthesized coatings contain 6–29 at.% of tungsten with a thickness of 1–2 μm. X-ray diffraction revealed the presence of only cubic WC1-x phase with a grain size of 2.5 nm. Rutherford backscattering technique was utilized to study elemental composition and structure of the coatings. X-ray photoelectron spectroscopy and Raman scattering were used to study the amorphous carbon component. The nanohardness is greatly influenced by tungsten concentration and is decreased from 26 GPa to 15 GPa by decreasing tungsten concentration. The critical load Lc2 demonstrates more complex behavior and the coatings spall off at 35 N. The coatings with tungsten concentration of 6–10 at.% show good tribological properties with coefficient of friction of 0.12–0.13 against Si3N4 ball and wear rate of 6.7 × 10−7 mm3/N·m.