Low friction PVD titanium–carbon coatings

PVD coatings based on diamond like carbon (DLC) can suffer from poor toughness if deposited using hydrocarbon gas. Incorporation of hydrogen is known to cause high compressive residual stresses and voids. Both these phenomena act detrimental on the coating fracture toughness. Thus, one way to improve the coating toughness, would be to use other deposition techniques and not include hydrocarbon gas in the process. Multilayering of coatings using very thin lamellae, especially with ductile components, has been shown to yield tougher PVD coatings. Especially for nitride multilayer coatings, this concept has proved successful. In this work, titanium–carbon coatings were deposited on steel using a novel hydrocarbon free multilayer process. The aim was to obtain coatings with overall good tribological and mechanical properties. It was found that the hydrocarbon free deposition process yielded well adherent TiC–C coatings with excellent tribological properties. Furthermore, the process was found to be easy to control, i.e. it was easy to deposit either titanium-rich coatings or low-friction carbon rich coatings.