Joining of SiO2f/SiO2 Composite to Metals Using AgCuTi Brazing Filler, the Joint Strengths and Microstructures

 SiO2f/SiO2 composite is a kind of advanced ceramic-based composite with good thermal-shock resistance, high ductility and low crack-sensitivity. In this paper, the composite was successfully joined to Invar alloy, Nb and Mo using AgCuTi brazing filler at 880°C for 10 min. A groove with width 0.6 mm and depth 1 mm was machined at the surface of the composite to be joined to improve the joint strength. During the brazing, some filler metal flew into the groove and combined with the composite. Therefore, the composite at the surface and those filler metals in the groove together formed a mixture layer, and this special layer would reduce the dismatch of the thermal expansion coefficient between the original composite and the metals to be joined, thus releasing the residual thermal stress in the joints. The test results at room temperature showed that the shear strengths of the composite with Invar alloy, Nb and Mo were 21.3 MPa, 26.4 MPa and 29.9 MPa respectively. According to micro-analysis results, these joints are characterized by laminated structure. Ag and Cu were detected at the fracture surfaces of the three kinds of joints by XRD method. In addition, Ni3Ti3O phase and TiSi2 phase were identified at the fracture surfaces of the composite/ Invar alloy and the composite/ Mo respectively.