Microstructure and Friction Properties of Cr-Doped Graphite-Like Carbon Films

Cr-doped graphite-like amorphous carbon films with various Cr contents were deposited on different substrates by unbalanced magnetron sputter ion plating technique.X-ray photoelectron spectroscopy,scanning electron microscopy,high resolution transmission electron microscopy and Raman spectroscopy were used to characterize the composition,surface morphology,microstructure and carbon bond structure of the films.The friction coefficient of films in dry friction and different lubricated conditions was measured by means of pin-on-disk friction testing.The results show that adding appropriate Cr into the graphite-like carbon films could keep the pure carbon films homogeneous and non-crystalline.Incorporating Cr into the film had significant influence on bond structure of carbon element in the film.With increasing Cr content,the fraction of sp2 carbon atom in the film increased first,and then decreased.Thereby,the carbon films incorporated with Cr could possess more sp2 carbon atoms than the pure carbon film.Appropriate amount of Cr incorporation could effectively reduce the friction coefficient of the graphite-like carbon film.The trend of friction coefficient of Cr-doped graphite-like carbon films obviously depended on the evolvement of bond structure of carbon element in the films with increasing Cr content.