Brazing SiO2f/SiO2 composite to Invar alloy using a novel TiO2 particle-modified composite braze filler

Abstract

To address the thermal stress issue in the brazed SiO2f/SiO2-Invar joints, a novel nano-TiO2p (p: particle) modified braze filler was developed. Wetting of the SiO2f/SiO2 composite by AgCuTi-based composite braze filler with different TiO2p contents were conducted first and a TiO2p content lower than 5 wt% was fixed. Then the microstructure evolution and mechanical performance of the SiO2f/SiO2-Invar joints brazed with different TiO2p additions and different brazing parameters were discussed. The highest shear strength of 30 ± 8 MPa was obtained at 910 °C/10 min. After using the TiO2p modified braze filler, the fracture probability of the SiO2f/SiO2-Invar joints dropped down by 75% (Taking 22 MPa as an example). Finally, a FEM was employed to get an in-depth understanding of the stress relief effects when using a TiO2p modified braze filler. Results show that the compressive stress on the SiO2f/SiO2 side dropped down by 30% after using a 2 wt% TiO2p modified braze filler. The in-situ formed CuxTi6-xO (x = 2, 3) phases played a key role in relieving the residual stress of the brazed joints. The development of the novel TiO2p modified braze filler was particularly suitable for the joining of the oxide ceramics and oxides-based composites.