Chemical vapor deposition of hard coatings: Part I: Ti-W-C by TiCl_4 + W(CO)_6 + CH_4 Part II: TiCN and TiN from tetrakis(dimethylamido)titanium

摘要

Ti-W-C thin films were deposited on stainless steel substrates (440C) by chemical vapor deposition (CVD) in a horizontal hot-wall reactor from a TiCl_4-W(CO)_6-CH_4-H_2-Ar gaseous mixture, at 1050 °C and at pressures ranging from 1 - 150 Torr. The structure of the Ti-W-C thin films was characterized using X-ray diffraction (XRD). The lattice constant of the Ti-W-C films shifts from that of TiC to W_xC_(1-x) with increasing W concentration in the thin films. A morphological analysis was carried out using scanning electron microscopy (SEM). It was found that the surface morphology was influenced by the W concentration and total flow. Compositional and binding characteristics of the Ti-W-C films were investigated by X-ray photoelectron spectroscopy (XPS). The associated hardness measured by nano-indentation ranged from 23- 32 GPa. The studies of transmission electron microscopy (TEM) and selected area diffraction (SAD) reveal the detailed microstructure of the Ti-W-C thin films and the presence of a WC phase. Additionally, generating a hard TiC phase at low temperatures has been attempted using tetrakis(dimethylamido)titanium (TDMAT) as the precursor and preliminarily, these films exhibit low hardness values between 2-5 GPa.