Effect of adding of SiC particulate on the microstructure and shear strength of SiC ceramic joint brazed with Si-24Ti alloy

In order to refine the grain size of TiSi2 silicide and reduce the formation of micro-defects in the joint, and thereby increasing the joint strength of SiC ceramic brazed with Si-24Ti (wt.%), a small amount of SiC particulates were added in the brazing alloy. The microstructure and mechanical strength of SiC joints was investigated by using field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction spectrometer, and shear strength test. The results indicated that SiC particulates enhanced the nucleation and grain refinement of the TiSi2 and Si phase. The adding of appropriate content of SiC (<1 wt.%) could effectively refine the size of TiSi2 phase and increase the fraction of Si-TiSi2 eutectic zone. However, excess addition of 1.5 wt.% SiC caused the coarsening of TiSi2 phase due to the clustering of added fine SiC particulates. With the increasing of SiC particulate content, the shear strength of the joints increased at first and then decreased. The maximum shear strength of 106.3 MPa of SiC joint was obtained for the joint brazed with 1 wt.% SiC addition, which was ~19% higher than that of the joint brazed without SiC particulates.