Tribology and use of dry-running ta-C films

Superhard tetrahedral bonded amorphous ta-C carbon coatings are predestinated for dry-running sliding components due to their unique combination of low friction and exceptional low wear. In this work, tribol. tests on ta-C coatings in oscillating and unidirectional sliding mode were performed under unlubricated conditions. Friction and wear coeffs. were measured in dependence of humidity and in high vacuum. After the tests the sliding surfaces were investigated with respect to transfer or triboreaction layers. Whereas tribol. behavior of ta-C is worse under drier conditions, surprisingly favorable friction and wear results were obtained under high vacuum.