OXIDATION TESTS OF CARBONACEOUS COMPOSITE-MATERIALS PROTECTED BY SI-B-C CVD COATINGS

This study has been carried out to evaluate the interest of chemical v apour deposition (CVD) (Si-B-C) layers to protect C/C and C/SiC materi als against oxidation between 850-degrees-C and 1700-degrees-C. The de posits have been made in a hot wall reactor by a classical CVD techniq ue. The coatings which were tested were either (Si-B-C) single layers, or SiC and (Si-B-C) multilayers. This study has shown that the contro l of the boron content of the (Si-B-C) layers and the thickness of eac h layer were essential. To achieve a good protection during several ho urs up to a temperature close to 1700-degrees-C, it seems that a trila yer SiC-(Si-B-C)-SiC is the most promising solution.