The performance of graphite-like carbon coatings deposited by pulsed magnetron sputtering

Abstract

Due to the small assembly gap between precision mechanical transmission parts, it is difficult to use lubricating media to reduce friction and prolong life. At present, the preparation of anti-friction lubrication coating on the surface of parts is a more effective means. The amorphous carbon coating has the advantages of simple preparation process, low deposition temperature and excellent anti-friction and wear properties. Amorphous carbon coating is early spalled because of internal stress accumulation. According to the principle of material preparation that the internal stress of amorphous coating can be reduced by the growth of amorphous and nanocrystalline synchronously, and a few doped metal elements aggregate and crystallize at the interface of amorphous carbon clusters driven by cohesive energy to spontaneously or combine with reactive gas to form high-density linear nanocrystals, thus inhibiting the peeling off of carbon clusters during wear process. The effect of the graphite target voltage on the microstructure and mechanical properties of graphite-like carbon (GLC) coatings was investigated. The microstructure of the coatings was characterized by Raman spectra, X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM). The properties of the coatings were measured by nanoindentation and ball and disc tribometer. The results showed that the deposition rate and the percentage of sp 2 bond increased obviously with increase of the graphite target voltage. The hardness increased to maximum (11.4 GPa) at the graphite target voltage of 700 V, which was related to high sp 3 /sp 2 bonding ratio. Moreover, the internal stress and coefficient of friction (COF) value decreased firstly and then increased slightly as the graphite target voltage increased from 640 to 720 V. The minimum COF and specific wear rate of the GLC coatings were obtained at the graphite target voltage of 700 V.