Processing of (PyC/TiC)_n multilayered coatings by pulsed CVD and RCVD

Abstract
Pyrocarbon/titanium carbide (PyC/TiC)_n multilayered coatings have been deposited on carbon substrates by P-RCVD which is a combination of pulsed chemical vapour deposition (P-CVD) with reactive CVD (RCVD). From thermodynamic calculations, a thin TiC sublayer deposited between two PyC sublayers should be stoichiometric. TiC and PyC growth rates have been investigated, as well as PyC consumption occurring during carbide growth by P-RCVD. Hence, this process allows to achieve a sharp control of each sublayer thickness. Furthermore, it seems possible to totally consume the PyC intercalated between adjacent carbide sublayers in order to obtain a multilayered carbide (TiC)_n. This method has been used to coat carbon fibres. The very first mechanical tests carried out on coated fibres are encouraging. The next step of this work lies in the study of such sub-micrometric coatings as interphases in ceramic matrix composites.