Preparation And Mechanical Properties Of CN_x-based Nanocomposite And Multilayer Films

This thesis focuses on the construction of amorphous carbon nitride (a-CNx) based nanocomposite films (TiCN films composed of nanocrystallines embedded) as well as multilayers (TaN/a-CNx multilayers), which are both prepared by direct current magnetron sputtering. Meanwhile, the relationship between the microstructure and mechanical properties of the films were investigated.1. The TiCN nanocomposite films with different compositions and structures were deposited by sputtering the Ti-C composite target under a constant low pressure with varies of nitrogen and argon flow rates. By the analysis of XPS, the N content in the films slightly increases with a simultaneous decrease in the C content, while the Ti content stays almost steady in the films with increasing the nitrogen flow rates. Without nitrogen, crystalline TiC film was obtained. After introducing nitrogen, the formation of crystallines TiN and Ti(C,N) with grain sizes of 5-10 nm occurred. Increasing nitrogen flow rate would increase the volume fraction ratio of TiN to Ti(C,N) in the TiCN films as well as the amorphous carbon content.2. The mechanical property tests of TiCN films show that under a nitrogen flow rate of 30 sccm, the TiCN film can achieve a combination of high hardness, good toughness and wear resistance.3. TaN/a-CNx-multilayers with modulation periods of 8.5-12 nm were deposited on Si wafers and titanium alloy substrate using direct current magnetron sputtering. Columnar structure exists in the TaN/a-CNx-multilayer with 0.5 nm-CNx, while the columnar crystalline can be better interrupted by thicker a-CNx layers.4. The hardness of all the TaN/a-CNx multilayers is higher than that of the single TaN film. Tribological properties of TaN/a-CNx multilayers deposited on Ti6A14V alloy substrates were tested by ball-on-disk tribometer at applied loads of 2-11 N. The lowest wear rate is obtained in the multilayer with 2 nm-CNx.