The electrochemical and mechanical properties of Ti incorporated amorphous carbon films in Hanks' solution

Ti incorporated amorphous carbon (a-C) films with variant Ti contents were prepared by the unbalanced magnetron sputtering process. Scanning electron microscopy, ultraviolet Raman spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy were used to characterize the microstructure of a-C films. The hardness and lubricated tribological properties were assessed using nanoindentation and ball-on-disk tribometer. As the Ti content in a-C films increases from 0 to 15.2 at.%, the sp3 volume fraction, the internal stress and the hardness of the films decreases gradually, while the disorder of sp2 bond increases. The electrochemical tests reveal that the a-C films with lower than 1.5 at.% Ti possess good corrosion resistance in Hanks' solution, while the a-C film with 15.2 at.% Ti is susceptible to crevice corrosion. The reduced friction of the a-C films is due to the sp2 bonded film surface and boundary lubrication of the Hanks' solution. The a-C film with 3.1 at.% Ti exhibits the best wear resistance in Hanks' solution among the studied films.