Mechanical properties of carbon nitride thin films prepared by ion beam assisted filtered cathodic vacuum arc deposition

C. Spaeth, M. Kühn, T. Chudoba, F. Richter
Technische Universität Chemnitz, Institut für Physik
D - 09107 Chemnitz
Germany

The mechanical properties of a tetrahedral amorphous carbon (ta-C) film and three carbon nitride (CN_x) films with nitrogen concentrations of 2 and 20 at.% were examined by means of indentation tests, abrasive wear tests and scatch tests. The incorporation of 20 at.% nitrogen in carbon films leads, on the one hand, to a moderately reduced hardness and wear resistance but, on the other hand, to a considerably increased adherence, making this material a promising candidate for tribological applications.
In a second part, a simple finite element (FEM) analysis is applied to confirm qualitatively that the maximum thickness achievable of films with intrinsic compressive stress can be increased by an interfacial layer with a stress gradient. Both effects, i.e. the improved adherence of carbon nitride and the smoothing of the stress depth profil, are used to increase the maximum film thickness of ta-C film on a tungsten carbide insert from about 1,5 to 3,1 mm.