AbstractSigmafibres (SM1240) produced by a chemical vapour deposition process using a 15μm tungsten wire corefor SiC deposition have a duplex coating of graphitic carbon and TiBx. Nodules present on the fibre surface are attributed to the deposition of the carbon coating over soot particles present on the substrate. Both the carbon and TiBxcoatings were stable in vacuum or air at temperatures up to 973 K. The nodules werefound to be sites of preferential attack by the titanium alloy matrix. The average number of nodules per fibre decreased more rapidly when the specimens were heated in air than in vacuum. It is suggested that the nodules may reduce the stability temperature of the coatings.MST/2028