Effects of Ti content on microstructure, mechanical and tribological properties of Ti-doped amorphous carbon multilayer films

Ti-doped amorphous carbon multilayer films with different Ti content are deposited on medical Ti6Al4V alloy using a closed field unbalanced magnetron sputtering. The microstructure and chemical composition are characterized by high resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The mechanical and tribological properties are evaluated by nanoindentation, Rockwell and scratch tests and ball-on-disk tribometer. The Ti content has a significant influence on the microstructure, mechanical and tribological properties of Ti doped a-C multilayer films. TiC nanocrystallites started to form in the a-C:Ti layer when the Ti target current density was above 2.58 mA cm− 2 during multilayer deposition process. Among these multilayers, the film deposited with a Ti target current density of 4.13 mA cm− 2 displays high hardness (25.2 GPa), high critical load (about 80 N), and low friction coefficient and wear rate in ambient air and in Hank's solution.