Role of Amorphous Silicon Carbide in Microstructure and Mechanical Properties of nc-TiC/a-SiC Nanocomposite Coatings Prepared by PECVD

摘要

Ternary Ti-Si-C coatings were synthesized on WC-Co substrates by a plasma-enhanced chemical vapor deposition (PECVD) technique using a gaseous mixture of TiCl_4, SiH_4, CH_4, Ar, and H_2. In this work, the effect of amorphous silicon carbide phase in Ti-Si-C coatings during deposition process was investigated using various instrumental analyses of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). The grain size of TiC crystallites decreased with increase of Si content because of the percolation phenomenon of amorphous silicon carbide. The Ti-Si-C coatings were characterized as a nanocomposite, which was composed of nano-sized titanium carbide (nc-TiC) crystallites and amorphous silicon carbide (a-SiC) at the Si content of 5.2 at.% in Ti-Si-C coatings, and showed the maximum hardness and Young's modulus of 33 GPa and 330 GPa, respectively. These values were significantly increased ones than those of a pure TiC (～21 GPa, 260 GPa).