Effect of Chromium on Structure and Tribological Properties of Hydrogenated Cr/a-C:H Films Prepared via a Reactive Magnetron Sputtering System**Supported by the National Natural Science Foundation of China under Grant Nos 51302116 and 51365016, and the Open Fund Item of State Key Laboratory of Solid Lubrication of Lanzhou Institute of Chemical Physics of Chinese Academy of Sciences under Grant No LSL-1203.

Abstract

Hydrogenated Cr-incorporated carbon films (Cr/a-C:H) are deposited successfully by using a dc reactive magnetron sputtering system. The structure and mechanical properties of the as-deposited Cr/a-C:H films are characterized systematically by field-emission scanning electron microscope, x-ray diffraction, Raman spectra, nanoindentation and scratch. It is shown that optimal Cr metal forms nanocrystalline carbide to improve the hardness, toughness and adhesion strength in the amorphous carbon matrix, which possesses relatively higher nano-hardness of 15.7 GPa, elastic modulus of 126.8 GPa and best adhesion strength with critical load (LC) of 36 N for the Cr/a-C:H film deposited at CH4 flow rate of 20 sccm. The friction and wear behaviors of as-deposited Cr/a-C:H films are evaluated under both the ambient air and deionized water conditions. The results reveal that it can achieve superior low friction and anti-wear performance for the Cr/a-C:H film deposited at CH4 flow rate of 20 sccm under the ambient air condition, and the friction coefficient and wear rate tested in deionized water condition are relatively lower compared with those tested under the ambient air condition for each film. Superior combination of mechanical and tribological properties for the Cr/a-C:H film should be a good candidate for engineering applications.