Formation of a Nanostructured Ti-Si-C-N Coating by Self-Organization with Reduced Amorphous Matrix

Abstract

A Ti-Si-C-N coating is deposited on AISI H11 hot working steel by plasma-enhanced chemical vapor deposition (PECVD) to investigate its micro- and nanostructure as well as its mechanical and thermal properties. Instead of a nanocomposite structure consisting of randomly oriented nanocrystalline (nc-) grains < 10 nm surround by an amorphous (a-) matrix, as usually found for these systems, this Ti-Si-C-N coating shows much larger Ti(C,N)-grains with a preferred (200) orientation identify by X-ray diffraction analysis. The strong texturing and grain sizes > 10 nm of the coating are confirmed by high-resolution transmission electron microscopy images. The coating's hardness is 46.3 GPa, making it equally hard to, e.g., nanocomposite Ti-Si-N coatings. These hardness values can only be achieved by a strong interface between a-matrix and nc-grains and small grain size. Despite 41.1 at.% carbon content, no significant quantity of a-C is found, as evidenced by Raman spectroscopy analysis. In order to investigate the oxidation behavior of the coatings, X-ray diffraction experiments are carried out at room temperature and in-situ in ambient atmosphere at elevated temperatures. The room temperature measurement shows a strong texturing of the Ti(C,N) lattice and yielded additional information on an anisotropic grain size.