Effect of composition and joining parameters on microstructure and mechanical properties of silicon carbide joints

Powder- and tape-like joining materials composed of SiC with Al-B-C (ABC) or Al-B 4 C-C (ABCC) sintering additives were used for the joining of SiC. The effect of interlayer composition, joining temperature and particle size of SiC on the microstructure and mechanical properties of SiC joints was studied. The results indicated that the tape-like adhesive introduces denser microstructure of interlayer relative to the powder-like one under the same conditions. It was demonstrated that using fine starting SiC powder instead of coarse one enhances the densification process of SiC joints. As joined at 1650°C, the microstructure of interlayer is improved gradually with the increasing Al content from 1 to 6 wt % in composition while slightly affected by the forms of additives, i.e. ABCC additive having the equal action to ABC one on the densification of joints. At higher joining temperature of 1750°C, the microstructure of interlayer containing 3 wt ‰ Al almost does not change while that containing 6 wt % degrades. SiC joints with strength higher than 344 MPa have been produced by using optimized joining variables, where the fracture of bonded SiC generally occurs within the SiC substrate.