Structural and mechanical properties of Cr–C–O thin films synthesized by a cathodic-arc deposition process

Chromium carbide and chromium oxide coatings deposited by physical vapor deposition methods have been successfully applied in molding industries for their excellent tribological performances. In addition, nanocomposite coatings have recently attracted interest because of their high hardness, wear resistance, and good thermal and chemical stability. In this study, Cr–C–O/a-C nanocomposite coatings were synthesized by cathodic-arc evaporation with plasma enhanced duct equipment. A pure CO2 reactive gas was introduced to react with chromium to form Cr–C–O/a-C nanocomposite coatings during the deposition process. The atomic content ratio of O/(C + O) increased with increasing CO2 deposition pressure. A nanocomposite structure of coexisting Cr2O3 and Cr7C3 crystallites and amorphous carbon phases was found in the Cr–C–O/a-C coatings. The nanoindentation test revealed the nanocomposite Cr–C–O/a-C coatings with the highest atomic content ratio of O/(C + O) possessed the highest hardness of 23 GPa.