FRICTION AND WEAR PROPERTIES OF HARD CARBON-FILMS FORMED ON CEMENTED CARBIDES BY DC PLASMA CHEMICAL VAPOR-DEPOSITION

A carbon film was formed on a WC-2%TaC-6%Co substrate from CH4 gas using d.c. plasma chemical vapor deposition (CVD). The effects of added argon and hydrogen gases and electrode power on deposition rate and hardness were investigated. The friction and wear properties of the coated carbides were investigated. The friction and wear properties of the coated carbides were measured. A film with a flat and smooth surface was obtained at a deposition rate of between 0.2 and 1.4 μm h-1 according to the CVD conditions. From the Raman spectra the film is estimated to be mainly composed of graphite-like carbon; however, no crystalline structure was observed using scanning electron microscopy. The coefficients of friction of the films were in the range 0.13-0.25 throughout dry sliding with hardened steel. Film with a high critical load in the scratch test generally showed better resistance to film flaking and wear. A film with a stable low coefficient of friction and superior wear resistance without flaking was obtained. The specific wear of this coated carbide was 1/23 that of the uncoated carbides.