Microstructure evolution and mechanical properties of SiC and Nb joint brazed with AgCuTi/(Sr0.2Ba0.8)TiO3-Cu/AgCuTi composite fillers

In this study, robust silicon carbide (SiC)-niobium (Nb) joints were obtained using a composite filler consisting of a novel type of negative thermal expansion (Sr0.2Ba0.8)TiO3 particle–reinforced Cu composites (SBT-Cu) and an AgCuTi active filler. A systematic investigation was conducted to analyze the brazing temperatures and SBT-Cu thickness affect the microstructure and mechanical properties of brazed joints. The results indicated that the shear strength of SiC-Nb joints brazed with AgCuTi + 80 μm SBT-Cu composite filler increased to 64 MPa at 900 °C for 15 min, which was an improvement of 146% over the strength of joints brazed without SBT-Cu. The addition of the SBT-Cu interlayer relieved the coefficient of thermal expansion mismatch among SiC, AgCuTi and Nb. Meanwhile, the calculation results verified that the residual stresses in the joints were substantially reduced and that the coefficient of thermal expansion of the composite filler was reduced.