High-temperature tribological performance of the Si-gradually doped diamond-like carbon film

Abstract

Silicon containing diamond-like carbon films is of value for engineering applications operating at the temperature above 200 °C. This work presents a Si-gradually doped diamond-like carbon film with increasing the Si content from outer layer to inner layer deposited by plasma-assisted reactive magnetron sputtering process. The microstructure, chemical bonding state and temperature-dependence tribological properties upto 500 °C of the film are investigated by using focused ion beam/transmission electron microscope (FIB/TEM), X-ray photoelectron spectroscopy (XPS) techniques and ball-on-disk tribometer, respectively. The results show that the as-deposited Si-gradually doped DLC film exhibit amorphous structure. The wear track tested at 500 °C are composed of carbon, SiO2 and silicon oxide. High-temperature tribological tests show that the friction coefficient values are 0.05 ± 0.01, 0.02 ± 0.004 and 0.09 ± 0.04, while the wear rates are 1.17 × 10−7 mm3/N·m, 1.65 × 10−7 mm3/N·m and 1.4 × 10−6 mm3/N·m at 300 °C, 400 °C and 500 °C, respectively. It is proposed that the improved high-temperature tribological properties of the Si-gradually doped DLC film benefit from its special composition structure that the inner layer with high Si content provides the required mechanical properties and the outer layer with low Si content reduces the friction coefficient as well as the wear rate.