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

The mechanical properties of a tetrahedral amorphous carbon (ta-C) film and three carbon nitride(CN,) films with nitrogen concentrations of 2 and 20 a t.% were examined by means of indentation tests, abrasive wear tests and sc ratch tests. The incorporation of 20 at.% nitrogen in carbon films leads, o n the one hand, to a moderately reduced hardness and wear resistance but, o n the other hand, to a considerably increased adherence, making this materi al a promising candidate for tribological applications. In a second part, a simple finite element (FEM) analysis is applied to conf irm qualitatively that the maximum thickness achievable of films with intri nsic compressive stress can be increased by an interfacial laver with a str ess gradient. Both effects, i.e. the improved adherence of carbon nitride a nd the smoothing of the stress depth profile, are used to increase the maxi mum him thickness of ta-C film on a tungsten carbide insert from about 1.5 to 3.1 mu m. (C) 1999 Elsevier Science S.A. All rights reserved.