Recently, nanocomposite coatings have attracted much interest because of their excellent mechanical performance and chemical stability. In this study, Cr-N-C-O nanocomposite coatings were synthesized by cathodic-arc evaporation with plasma enhanced duct equipment. Nitrogen and CO(2) reactive gases were introduced to react with chromium to form Cr-N-C-O nanocomosite coatings during the deposition process. The plasma in a cathodic arc evaporation process used for the deposition of Cr-N-C-O coatings was studied by an optical emission spectrometer (OES). With the introduction of nitrogen and CO(2) reactive gases into the chamber, high density of evaporated chromium catalyzes the decomposition of nitrogen and CO(2) reactive gases, and induces the formation of Cr-N-C-O films. The emission intensity of Cr atoms decreased with increasing N(2)/(N(2) + CO(2)) flow rate ratio. It showed the deposition rate increased at higher CO(2) flow rate. A nanocomposite structure of coexisting CrN, Cr(2)N and Cr(2)O(3) crystallites and amorphous carbon phases was found in the Cr-N-C-O coatings. (C) 2009 Elsevier B.V. All rights reserved.