EFFECTS OF JOINING PRESSURE AND DEFORMATION ON THE STRENGTH AND MICROSTRUCTURE OF DIFFUSION-BONDED SILICON-CARBIDE

The effects of joining pressure and deformation on the strength and microstructure of diffusion-bonded SiC were examined using a hot-press to apply varying amounts of interfacial pressure and a close-fitting die to restrict deformation. SiC substrates were successfully diffusion bonded at 1950-degrees and 2100-degrees-C. Joints which had uniform grain structure across the joint interface and bend strengths up to 300 MPa (44 ksi) were achieved. Pressing pressure was found to be a requirement for producing reasonable joint strength. It was also found that macroscopic deformation (> 4% joint area expansion) is not necessary for effective diffusion bonding. Various methods for joining SiC are reviewed with regard to ease of processing, use limitations, and joint strength.