Influence of nitrogen ion implantation on tribological properties of nanocrystalline diamond films

Ion implantation is commonly used as a method to modify the surface or near-surface properties of materials and to improve their mechanical properties. In this paper, nanocrystalline diamond films, prepared by a microwave plasma enhanced chemical vapour deposition, were implanted using 110 keV nitrogen ions under a fluence ranging from 1x1016 to 1x1017 ions cm-2. The friction and wear properties of the nanocrystalline diamond films in ambient atmosphere, and the surface structure and chemical state of the films, without and with the implantation were investigated. The results showed that adhesive friction took place between the nanocrystalline diamond film without ion implantation and a ruby ball in the friction process, which caused high friction coefficient and wear of the ruby ball. Ion implantation changed the surface chemical state of the nanocrystalline diamond films. A layer of oxygen-containing groups on the nanocrystalline diamond films produced by the high fluence nitrogen implantation played an important role in reducing the adhesive friction between the films and the ruby ball, and decreasing the friction and wear of the ruby ball. (author)