Titanium carbide/carbon nanocomposite hard coatings: A comparative study between various chemical analysis tools

Titanium carbide/carbon nanocomposite hard coatings, which consist of TiC nanoparticles buried in amorphous carbon matrix, are prepared by a hybrid plasma process combining magnetron sputtering of a titanium target and plasma enhanced chemical vapor deposition using methane as a source for the growth of amorphous carbon. A particular attention was paid to the comparison of the surface and the bulk chemical compositions of the films determined by different analysis techniques: X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry (RBS), wavelength dispersive X-ray spectroscopy (WDS) and energy dispersive X-ray spectroscopy (EDS). XPS and EDS show an underestimation in carbon concentration compared to RBS and WDS which provide similar values. This underestimation is more important in case of XPS and it is mainly attributed to the presence of oxygen contamination on the surface of the films strongly bonded to titanium. In case of EDS, the underestimation is related to the poor sensitivity of the used probe in regard to light elements such as carbon. Moreover, the structure of the coatings has been extensively probed by transmission electron microscopy, which has shown that the size of the TiC nanoparticles shrinks when increasing the carbon content within the films. We further demonstrate that this structural evolution has a direct impact on the hardness of the coatings which gets reduced when the grain size decreases. •TiC/a-C:H nanocomposite hard coatings are synthesized by a hybrid plasma process.•Film compositions given by XPS, EDS, WDS and RBS are compared and discussed.•A TEM extensive study has revealed the film structural evolution.•Microstructure and film composition are controlled by tuning the plasma parameters.•Increasing the carbon content in the coatings leads to a decrease in their hardness.