Structural characterization of nanocomposite Ti–Si–N coatings prepared by pulsed dc plasma-enhanced chemical vapor deposition

Abstract

Ti–Si–N coatings have been investigated widely in recent years due to their unique nanocomposite microstructure and attractive properties of superhardness, fairly good oxidation-resistance nearly to 1000 °C, etc. In this study, Ti–Si–N coatings have been prepared by pulsed dc plasma-enhanced chemical vapor deposition in an industrial-scale chamber. Structural characterization of Ti–Si–N coatings was examined by x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron micrograph, and transmission electron microscopy. The results show that: (1) The microstructure of Ti–Si–N coatings varies significantly with the processing parameters, (2) the microstructure can be confirmed as nanocomposite Ti–Si–N where nanocrystalline TiN and/or TiSi2 particles are embedded into an amorphous matrix of Si3N4, and (3) the nanocrystals have a multioriented microstructure. However, the silicon content in Ti–Si–N coatings and coating thickness as well as crystalline size all increase when the inlet gas ratio of X=[SiCl4/(TiCl4+SiCl4)]% increases. Whereas the microhardness of the coatings first increases with increased Si content, microhardness reaches a maximum value of about Hv5800 at 13 at. % Si and then decreases slightly.