Microstructure and tribological properties of TiSiCN composite coatings with different carbon contents deposited by plasma-enhanced magnetron sputtering

TiSiCN composite coatings with different C contents were prepared on Cr buffer layer by plasma-enhanced magnetron sputtering. The structure, composition, surface, and cross-sectional morphology of the coatings were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy, scanning electron microscope, and atomic force microscope. The hardness, elastic modulus, and tribological performance of the coatings were evaluated by nanoindentation and reciprocating friction tests. The results showed that the TiSiCN composite coatings are amorphous structure composed of TiCN compound and microcrystalline graphite, and amorphous phases. The increase of C content changed the content and distribution of TiCN ceramics nanocrystal, amorphous Si3N4 and amorphous carbon (sp(3)- and sp(2)-hybridized C), thus affecting the hardness and friction behavior of the coatings. The hardness of the composite coatings was related to the content of TiCN phase and sp(3)-C in the coatings. The TiSiCN composite coating with C content of 68.2% had lower coefficient of friction and the lowest wear rate.