Microstructure and mechanical properties of SiC joint with an in-situ formed Cheek for SiC-TiB2 composite interlayer

Diffusion bonding of SiC ceramic with in-situ formed SiC-TiB2 composite interlayer by reactive spark plasma sintering with B4C-Ti3SiC2-Si powder mixture was investigated. It was found that a dense composite interlayer between the SiC ceramic substrate could be obtained at 1600 degrees C for 10 min. Granular-shaped SiC with sub micron-size and elongated TiB2 with micro-size were uniformly distributed in the bonding layer. The joint strength and hardness of the composite interlayer increased as the joining temperature increased up to 1600 degrees C due to the improved relative density and the higher fraction of elongated TiB2 phase. The grain growth and formation of micro-cracks deteriorated the mechanical strength of the 1700 degrees C joint. The maximum shear strength of 128.0 +/- 7.3 MPa was achieved for the joint bonded at 1600 degrees C. The toughening mechanisms of crack deflection, crack bridging and crack branching, and hardening mechanism of dual phase strengthening were observed in the morphology of indentation cracks.