Beneficial effects of B4C addition on the microstructure and mechanical properties of SiC ceramic joints diffusion bonded with Ti3SiC2

Abstract The interfacial microstructure and mechanical properties of SiC ceramic joints diffusion bonded via spark plasma sintering with a powder mixture of Ti 3 SiC 2 and B 4 C were investigated. The content of B 4 C ranging from 0 to 20 wt% was added into Ti 3 SiC 2 . Microstructure analysis results indicated that B 4 C in-situ reacted with Ti 3 SiC 2 to form fine-sized TiB 2 , TiC, SiC, and carbon in the joint. The volume fraction of these reaction formed phases and coefficient of thermal expansion of the composite interlayer were calculated. The proper addition of B 4 C (5–15 wt%) was beneficial for the improvement of joint strength. The optimal amount of B 4 C addition was 7.5 wt%. The shear strength of the joint bonded with 7.5 wt% B 4 C addition reached 112.5 ± 8.3 MPa, which was 53.9% higher than that bonded without B 4 C addition. Vickers hardness of the composite interlayer was enhanced with the B 4 C addition. Toughening mechanisms including delamination and kinking of Ti 3 SiC 2 , crack deflection, crack bridging, and crack branching were observed in the composite interlayers.