EFFECT OF TIB2, TIC AND TIN PROTECTIVE COATINGS ON TENSILE-STRENGTH AND FRACTURE-BEHAVIOR OF SIC MONOFILAMENT FIBERS

TiB2, TiC and TiN have been studied as potential protective coatings t o prevent the deleterious interfacial reactions between SiC fibres and Ti alloy matrices. These coatings have been deposited on to resistive ly heated SiC monofilament fibres at reduced pressure in a cold wall r eactor by a chemical vapour deposition technique. Microstructure, stre ngth and fracture properties of SIC fibres coated with the different p rotective coatings were evaluated and compared. The adhesion of the Ti C coating on SiC fibre was comparatively weaker than that of the TiB2 coating. The strength of SiC monofilaments coated with TIC was lower t han that of monofilaments coated with TiB2. The morphology of TiN coat ings revealed severe cracking and spalling. Results of a thermoelastic stress analysis were helpful in interpreting these experimental obser vations.