Thermal stability of interfaces in Ti-6Al-4V reinforced by SiC Sigma fibers

Interfacial reactions in Ti-6Al-4V/SiC Sigma fibres (coated with carbon and TiB2) were studied at different temperatures (600, 700 and 1000 °C). Interface microstructure was investigated by scanning electron microscopy and Auger electron spectroscopy. A simulation of the chemical phenomena occurring at the interfaces was carried out using powders of pure titanium, carbon and TiB2; the reaction products were identified by X-ray diffraction. The double coating of Sigma fibres is effective in delaying detrimental reactions with the matrix. At the interfaces matrix/TiB2 and TiB2/C, the TiB and TiCx phases form, respectively. The protective coating of fibres shows a lifetime greater than 1000 and 750 h at 600 and 700 °C, respectively.