CNx films were prepared on cemented carbide substrates by a pulsed bias arc ion-plating method with two graphite targets and using N-2/Ar mixture gases. The effects of the deposition parameters, such as substrate negative-bias voltage, duty cycle, and nitrogen flow rate, on the structures and properties of CNx films were investigated using Raman spectra and nanoindentation. The properties of CNx films are closely related to the film structures. For CNx films deposited at a different bias voltage, the CNx film deposited at a bias voltage of -300 V had the highest hardness. The I-D/I-G ratio and G peak position decreased and then increased with increasing bias voltage, and the minimum values, which correspond to the highest sp(3) content, were obtained at a bias voltage of -300 V. For the CNx films deposited at different duty cycles, the hardness and elastic modulus decreased with increasing duty cycle. For the CNx films deposited at different nitrogen flow rates, the results show that first the I-D/I-G ratio decreases and sp(3) content increases with increasing nitrogen flow rate, and then the I-D/I-G ratio increases and sp(3) bond content decreases after the nitrogen flow rate exceeds 10 SCCM (SCCM denotes cubic centimeter per minute at STP). The hardness and elastic modulus of the CNx film prepared at a nitrogen flow rate of 10 SCCM reached the maximum values of 32.1 and 411.8 GPa, respectively. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3482010]