The growth of Ti3SiC2 coatings onto SiC by reactive chemical vapor deposition using H2 and TiCl4

Abstract

(SiC/Ti3SiC2)n multilayered coatings composed of n layers alternately of continuous SiC and Ti3SiC2 sub-layers were prepared on carbon substrates. The method consists in depositing SiC by classical chemical vapor deposition (CVD) and then producing a new Ti-containing sub-layer from a reaction between SiC and a H2/TiCl4 gaseous mixture by reactive CVD (RCVD), and repeating this sequence n times. In accordance with thermodynamics, this RCVD method produces only pure TiC sub-layers when a low dilution ratio of TiCl4 in H2 (R=[H2]/[TiCl4]) is used. With a high R value, the growth of pure Ti3SiC2 thin continuous sub-layers from solid–gas reaction is observed for short deposition times. But for long deposition times, the simultaneous growth of additional Ti5Si3Cx and TiC sub-layers occurs from solid state diffusion when the initial Ti3SiC2 sub-layer thickness exceeds about 1 μm. In that case, the repeating of the sequence results in the further conversion of the additional phases into new Ti3SiC2 sub-layers from solid state reactions involving TiSi2 as an intermediate phase and SiC.