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. (C) 2015 Elsevier B.V. All rights reserved.