Microstructure, mechanical and tribological properties of a-C/a-C:Ti nanomultilayer film

An a-C/a-C: Ti multilayer film with a bilayer period of 40 nm was deposited on medical Ti6Al4V alloy using a closed field unbalanced magnetron sputtering. The microstructure and chemical composition of the multilayer film were investigated by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The mechanical and tribological properties were evaluated from nanoindentation, Rockwell and scratch tests, and ball-on-disk tribometer. Nanoindentation tests showed that the hardness of the multilayer film reached 25 GPa with good toughness. Due to the interface effect, the adhesion strength of the nanomultilayer was significantly improved. In humid air without lubrication, the a-C/a-C: Ti nanomultilayer film had a low friction coefficient of 0.080 and wear rate of 1.95 × 10− 16 m3 N− 1 m− 1 at a load of 10 N. While in Hanks' solution, the film exhibited lower friction coefficient of 0.074 and wear rate of 4.25 × 10− 17 m3 N− 1 m− 1.