The effect of high temperature heat-treatment on the strength of C/C to C/C–SiC joints

Abstract

Joining of carbon fiber reinforced carbon matrix composite to a carbon fiber reinforced C–SiC dual matrix composite has been realized through a reaction joining process using boron-modified phenolic resin with micro-size B 4C and nano-size SiO 2 powder additives. The effect of the heat-treatment temperature on the retained strength of the joints, calculated by dividing the strength of the heat-treated joints by the strength of the joints before heat-treatment, was studied. The maximum retained strength of the joints is 91.9% after heat-treatment at 1200 °C for 30 min in vacuum, indicating good heat-resistance of the joints. The interlayer with a thickness of about 25 μm is uniform and densified. There are no obvious cracks or pores at the interfaces. The interlayer is composed of B 4C, SiO 2, glassy carbon, B 2O 3 and borosilicate glass. Si diffuses from the interlayer into the substrates and reacts with carbon to form SiC. Both B and O migrate from the interlayer into the substrates, contributing to the interfacial bonding. The B 4C and the SiO 2 powder additives contribute to the densification of the interlayer, the bonding at the interfaces and the heat-resistance of the joints.