Influence of SiC content on the oxidation of carbon fibre reinforced ZrB2/SiC composites at 1500 and 1650 degrees C in air

The microstructure and the oxidation resistance in air of continuous carbon fibre reinforced ZrB2-SiC ceramic composites were investigated. SiC content was varied between 5-20 vol.%, while maintaining fibre content at similar to 40 vol.%. Short term oxidation tests in air were carried out at 1500 and 1650 degrees C in a bottom-up loading furnace. The thickness, composition and microstructure of the resulting oxide scale were analysed by SEM-EDS and X-Ray diffraction. The results show that contents above 15 vol.% SiC ensure the formation of a homogeneous protective borosilicate glass that covers the entire sample and minimizes fibre burnout. The scale thickness is similar to 90 mu m for the sample containing 5 vol.% SiC and decreases with increasing SiC content.