Characterization and properties of Ti-containing amorphous carbon nanocomposite coatings prepared by middle frequency magnetron sputtering

Ti-containing amorphous carbon (Ti-aC) nanocomposite coatings were deposited by using a modified closed field twin unbalanced magnetron sputtering system which is arc assisted and consists of two circles of targets, at a substrate temperature of 100 °C. The coatings exhibit good mechanical properties that are greatly influenced by the substrate bias voltage and Ti concentration. For coatings prepared at a bias of 100 V, the hardness increases from 12 GPa at a Ti concentration of 1 at.% to 27 GPa at 31 at.%. High-resolution transmission electron microscopy showed that the coatings contain Ti nanocrystals embedded in the amorphous carbon matrix. The average grain size decreases from 10 nm at 4 at.% Ti to 6 nm at 31 at.% Ti. The coating with 4 at.% Ti exhibits excellent tribological performance with a low friction coefficient of 0.07 and a wear rate of 1.4 × 10− 16 m3/Nm.