Effect of pulsed bias voltage on the structure and mechanical properties of Ti–C–N composite films by pulsed bias arc ion plating

• Ti–C–N composite films were deposited by pulsed bias arc ion plating.
• The films consist of nc-Ti(C,N) phase imbedded into amorphous carbon matrix.
• The maximum value of hardness and fraction of crystalline phase were obtained at −300 V.

The influence of pulsed bias voltage on the structure and mechanical properties of Ti–C–N composite films prepared by pulsed bias arc ion plating was systematically investigated. The microstructure, surface morphology and bonding structure of the films were evaluated with grazing incidence X-ray diffraction, high resolution transmission electron microscopy, Raman and X-ray photoelectron spectroscopy, and scanning electron microscope. The mechanical properties such as hardness and elastic modulus were measured by nano-indentation. A composite structure consisting of nanocrystallites Ti(C,N) and amorphous carbon is observed. The surface morphology indicates that the size and amount of macroparticles at the film surface decrease with the increase of bias voltage. Applying a bias voltage of −300 V in Ti–C–N films induces strong crystalline characteristic. However, other bias voltages cause a tendency to a lower degree of crystallinity and an enhanced fraction of amorphous phase. With increasing the bias voltages from −100 V to −700 V, the corresponding hardness and elastic modulus increase firstly and then decrease, reaching a maximum value of 32.5 GPa and 367.4 GP at the bias voltage of −300 V.