Preparation and tribological behavior of TiN/a-C composite films deposited by DC magnetron sputtering

TiN/amorphous carbon (a-C) composite films were deposited onto steel substrate by DC magnetron sputtering with different ratios of graphite to Ti in target and at a substrate temperature of 200 °C. The hardness, composition, morphology and microstructure of the composite films were characterized by energy dispersive X-ray spectrum (EDS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). In the graphite/Ti range of 0.5–2.0 of the combined target, the ratio of Ti to N in the films was hardly dependent on the graphite/Ti ratio, and the films exhibited a (2 2 2) preferred orientation and a columnar structure at lower graphite/Ti ratio. The tribological properties were investigated using a ball-on-disk tribometer in humid air. With increasing the graphite/Ti ratio, the friction coefficient and wear rate of the composite films decreased. The composite film deposited at the graphite/Ti ratio of 1.0 showed a low friction coefficient and high wear resistance in humid air.