The mechanical properties and microstructure of Ti–Si–N nanocomposite films by ion plating

The hardness and microstructure of Ti–Si–N films were investigated. The hardness of the films increased with increasing Si content of the films, and the maximum hardness, more than Hk4500 was obtained within the range of 0.3–0.5 of Si/(Si+Ti) ratio. The X-ray diffraction (XRD) data showed only TiN peaks and no Si–N peaks. The XRD peaks of TiN of the Ti–Si–N films became broad with Si content of the films. The TiN crystallite sizes calculated from the FWHM values of TiN diffraction peaks decreased with the increment of Si content of the films. It became clear that when the Si/(Si+Ti) ratio of the films was more than 0.1, TiN crystallite sizes decreased to less than 7 nm. The thin amorphous grain boundaries of Si–N and the TiN crystallites in size of approximately 5 nm were observed by high resolution transmission electron microscopy. It was assumed that the high hardness of the Ti–Si–N nanocomposite films was due to a halt of propagation of dislocations by an amorphous phase on TiN grain boundaries in addition to nano-scale size of TiN crystallites brought by inhibition of crystal growth of TiN through an amorphous Si–N phase.