TRIBOLOGICAL PROPERTIES OF DIAMOND-LIKE CARBON AND RELATED MATERIALS

Amorphous hard carbon films are often called diamond-like carbon (DLC) owing to their hardness, extreme wear resistance, and generally low friction coefficients. The tribological properties of DLC span a wide range of values depending on the deposition condition but they have several common features: friction coefficients which are extremely low in ultrahigh vacuum or dry nitrogen but high in dry oxygen, and very high wear resistance in vacuum and in ambient atmosphere, depending however on the deposition conditions. Loss of hydrogen from hydrogenated DLC results in loss of wear resistance and an increase in the friction coefficient in vacuum. The paper will present the tribological properties of pure DLC films and related materials, in different evaluation environments. The properties will be related to the deposition method and conditions and the mechanisms proposed for explaining the very low friction coefficients of DLC will be discussed. The effects of thermal annealing on the tribological properties of DLC will also be addressed.