Properties of the Nonhydrogenous Diamond-Like Carbon Thin Film on the 20CrNiMo Surface by the Hollow-Cathode Glow Discharge

Nonhydrogenous Diamond-like carbon (DLC) thin film was deposited on the surface of 20CrNiMo alloy by hollow cathode glow discharge technique. The high-purity graphite was selected as the cathode and Ar as the working gas. It is aimed to reduce the friction coefficient of the 20CrNiMo and to improve the property of the wear-resistance. The structure of the DLC thin film was analyzed by Laser Raman spectroscope. The surface morphology was observed through Atomic Force Microscope (AFM). The adhesion between the DLC thin film and the substrate was investigated with the scribe testing. The morphology of the scratch was observed by the Scanning Electron Microscope (SEM). The friction and wear behavior of the DLC thin film under dry sliding against GCr15 steel was evaluated on a ball-on-disc test rig. The results showed that it was feasible to prepare a DLC thin film of 0.6 μm thickness by this experimental process. The surface roughness Ra was about 7∼8 nm. The DLC thin film has a good adhesion of critical load 52N. It has been found that the DLC thin film has excellent friction and wear-resistant behaviors. The friction coefficient of the 20CrNiMo substrate was about 0.50 under dry sliding against the steel, while the DLC thin film experienced much abated friction coefficient to 0.15 under the same testing condition.