Chemical vapour deposition of PyC–SixCy–SiC–Si3N4 multilayer with graded C…SiC transition

A multilayer protective coating of C/C-SiC composites is proposed and realised by chemical vapour deposition (CVD). It consists of a pyrocarbon layer for bonding and smoothing the substrate surface, and a controlled graded SixCy transition coating for a stoichiometric SiC layer. Si3N4 and Al2O3 topmost layers provide oxidation and corrosion protective properties. This complete layer stacks put in a single growth process into a horizontal ‘Cold Wall’ reactor chamber equipped with high frequency (HF)—heating under atmospheric and at low pressure. Microstructure, chemical composition, and morphology of the layers are investigated by SEM, EDX, EPMA, ESCA, and micro-Raman spectroscopy. The line-scan electron-probe microanalysis and Raman spectroscopy on the cross sectional layering of the samples shows the distribution of the various elements and their composition according to the controlled deposition process. ESCA measurements identify the formation of Si3N4.