Friction and wear characteristics of ceramic nanocomposite coatings: Titanium carbide/amorphous hydrocarbon

Friction and wear characteristics of titanium-containing amorphous hydrocarbon (Ti-C:H) coatings were measured during unlubricated sliding against WC-Co. These Ti-C:H coatings consist of nanocrystalline TiC clusters embedded in an amorphous hydrocarbon (a-C:H) matrix, i.e., they are TiC/a-C:H nanocomposites. The elastic modulus and hardness of the coatings exhibit smooth variations with increasing Ti composition. In contrast, a relatively abrupt transition occurs in the friction coefficient and wear rate of the coatings over a relatively narrow (20-30 at. %) Ti composition range. Our results reveal bimodal friction and wear behaviors for the TiC/a-C:H nanocomposites, a-C:H like at Ti compositions below 20%, and TiC like at Ti compositions above 30%. The two different wear mechanisms that operate as the volume fraction of nanocrystalline TiC clusters changes are discussed. (C) 2001 American Institute of Physics.