Boron carbide films are attractive materials for use as tribologcal coatings for low and high operating temperatures, especially for applications that require high hardness. The properties of boron carbide films prepared by cathodic arc using a heated B4C cathode are investigated. The B: C ratio in the film was about 3, and the only detected impurity was oxygen with a content below 5%. The effect of substrate bias on the film characteristics was studied. A direct correlation between hardness and elastic modulus and bias voltage applied to the substrate was observed for bias voltages in the interval of 0 - 500 V. Microstructure and chemistry of the films were investigated using X-ray diffraction, electron microscopy and X-ray absorption spectroscopy. (C) 2003 Kluwer Academic Publishers.