Multilayer hard carbon films with low wear rates

Vacuum arc deposition has been used to grow thin, ultrahard carbon films. Multilayer structures consisting of four alternating double layers of carbon with sp(3) contents of 80 and 40%, respectively, were grown using a pulse bias technique for ion energy control. The relative proportion of the soft layer (40% sp(3) content) in the multilayer structure was varied from 10 to 90%. The hardness of the multilayer structure is a weighted average of the hardnesses of the component layers. The overall compressive growth stress is less than would be expected from the proportions of the layer components. Pin-on-disk wear testing showed that multilayer films have a lower wear rate than monolithic films especially at higher loads. The lowest wear rate was measured in a film with alternating layers of approximately equal thicknesses of the hard and soft layers.