CRACKING BEHAVIOR OF CARBON COATING ON SIC FIBER AND RESIDUAL-STRESSES IN TI SIC MMCS/

The main purpose of this present work was to study the cracking behavi our of carbon coating on SiC fibre and residual stresses in Ti/SiC met al matrix composites (MMCs) during thermomechanical cycling. Acoustic emission (AE), scanning electron microscopy (SEM). transmission electr on microscopy and X-ray photoelectron spectroscopy (XPS) were used in order to get more information of Ti-MMC damage mechanisms under tensil e stress at room and elevated temperatures. Ti-6Al-4V/SiC (sigma fibre 1140 plus) composite was used. C coating layer (approximate to 5 mu m ) clacking and interface debonding were found after the thermomechanic al testing. TiC was found at the carbon/matrix interface was found by means of XPS. The AE peaks and SEM observations reveal that the AE sig nals come mainly from SiC-C debonding and cracking at room temperature with an increase likelihood of C/matrix debonding at high temperature s and stresses. (C) 1998 Elsevier Science S.A.