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 Ti3SiC2 and B4C were investigated. The content of B4C ranging from 0 to 20 wt% was added into Ti3SiC2. Microstructure analysis results indicated that B4C in-situ reacted with Ti3SiC2 to form fine-sized TiB2, 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 B4C (5–15 wt%) was beneficial for the improvement of joint strength. The optimal amount of B4C addition was 7.5 wt%. The shear strength of the joint bonded with 7.5 wt% B4C addition reached 112.5 ± 8.3 MPa, which was 53.9% higher than that bonded without B4C addition. Vickers hardness of the composite interlayer was enhanced with the B4C addition. Toughening mechanisms including delamination and kinking of Ti3SiC2, crack deflection, crack bridging, and crack branching were observed in the composite interlayers.