Study of TiC Coatings on Nicalon Fibre Prepared by Pressure-Pulsed Reactive Chemical Vapour Deposition at Low Pressure

Abstract

TiC coatings on Nicalon SiC-based fibres were obtained in two steps; the first step consisted in converting the surface of the Nicalon fibre into nanoporous carbon by a chlorine treatment at 773 K, the second step consisted in converting this nanoporous carbon film into TiC by pressure-Pulsed Reactive Chemical Vapour Deposition at low pressure with a H2/TiCl4 mixture at 1373 K. The coatings were characterized by X-ray photoelectron spectroscopy, Auger electron spectroscopy and scanning and transmission electron microscopies. Mechanical assessment was achieved by tensile tests at room temperature. The conversion rate of C into TiC was studied varying the number of H2/TiCl4 pulses from 0 to 100. The formation of a thin interlayer between the fibre and the nanoporous carbon coating was revealed as soon as only 20 pulses are used. The conversion rate increases with the number of H2/TiCl4 pulses while the fibre failure stress decreases almost linearly.