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Effect of N content on the microstructure and tribological properties of TiSiCN composite coatings

TiSiCN composite coatings with different N contents based on Cr buffer layer were prepared by plasma-enhanced magnetron sputtering. The surface and cross-sectional morphology, composition, and structure of the coatings were evaluated by scanning electron microscope with energy dispersive spectroscopy, atomic force microscope, x-ray photoelectron spectroscopy, x-ray diffraction, and Raman spectroscopy. The hardness, elastic modulus, and tribological performance were investigated. The results showed that with the addition of N content, the proportion of sp3-hybrized C bonds and amorphous Si3N4 in TiSiCN coatings gradually decreased, while the proportion of graphite phase and CNx gradually increased. The decrease in the sp3—C bonding ratio leads to the decrease of coating hardness, and the composite coating with N content of 7.3% has the highest hardness at 13.2 GPa. The friction experiments exhibited the self-lubrication feature of the internal graphite phase, and the strengthening of moderate amounts of the hard phase can significantly reduce the wear rate. The TiSiCN composite coating with N content of 13.2% had the lowest wear rate.