Design and performance optimization of SiC_p/CA composite filler for improved microstructure and mechanical properties in SiC ceramic joints

Glass-ceramic is commonly considered to be an excellent bonding filler for SiC ceramic joints. However, the mismatch in the coefficient of thermal expansion (CTE) between the filler and SiC may induce microcracks in the joint, leading to a subsequent deterioration in mechanical performance. To address this issue, this study introduces silicon carbide ceramic particles into CaO-Al₂O₃glass-ceramic (SiC_p/CA composite filler) to mitigate the adverse effects on the joint microstructure and mechanical properties caused by the mismatch of CTE. The feasibility of the SiC_p/CA combination was preliminarily explored through wetting experiments. The thermal expansion measurement on the SiC_p/CA composite filler indicate that adding SiC_pto the CA glass-ceramic can closely match its CTE with that of the SiC substrate, thereby minimizing the residual stress in the joint. When SiC_p/CA composite filler is used to join SiC ceramics, the results demonstrate a uniform microstructure in the joint, with a well-bonded interface. The joint structure is consist by Ca₁₂Al₁₄O₃₃and SiC_p. When using 20 wt% SiC_p/CA composite filler to join SiC ceramic, the shear strength of the joint is 50 MPa, marking a substantial 100 % increase compared to the joints using CA glass-ceramic under identical conditions. This highlights the effectiveness of incorporating SiC_pinto CA glass-ceramic in significantly enhancing the mechanical properties of SiC joints.