Structural and microtribological studies of Ti-C-N based nanocomposite coatings prepared by reactive sputtering

Ti-C-N thin films were synthesized at near room temperature by reactive magnetron sputtering of titanium and graphite targets in Ar or Ar/N2 mixtures. The microstructure and chemical composition of the coatings were studied by transmission electron microscopy, atomic force microscopy (AFM), electron diffraction, X-ray diffraction, X-ray photoelectron spectroscopy and electron energy loss spectroscopy. For a pure Ar atmosphere, a microstructure constituted by small grains (10-20 nm) of a TiC phase encapsulated into an amorphous matrix is observed. AFM lateral force mapping shows a strong frictional contrast between the two phases. When nitrogen is introduced in the gas phase during preparation, the granular microstructure is not seen and the chemical composition is enriched in amorphous nonstoichiometric CNx phases (a-CNx) with different content of nitrogen (0.5≤x≤0.7). The type of structure and chemical bonding of the Ti-C-N films are correlated with the tribological properties at the microscopic level in order to establish the synthesis conditions leading to the nanocomposite formation.