Properties of ta-C Films for Tools and Machinery Parts

The pulsed vacuum arc discharge is an effective technology for the deposition of ta‐C coatings on tools and machinery parts. The properties of these carbon coatings differ substantially from conventional hard nitride films particularly with regard to hardness and wear‐resistance. The paper shows analytical results of ta‐C films in comparison to such hard coatings. Thereby different methods are applied for determination of adhesion, friction, wear‐resistance, and indentation hardness. A simple correlation was found between indentation hardness and wear‐resistance over a wide range of hard materials. Furthermore, all investigated films have a strong adhesion on steel in conventional Rockwell tests. But in scratch tests with increasing normal forces brittle ta‐C films delaminate at lower forces from the surface compared to nitride coatings.