Microstructure evolution and mechanical properties of ZrO2/ZrO2 joints brazed with Ni–Ti filler metal

Abstract

Ni–Ti alloy was used as brazing filler to join ZrO2 ceramics and reliable joints were achieved. The effects of brazing temperature on the interfacial microstructure and mechanical properties of ZrO2/Ni–Ti/ZrO2 joints were investigated, the microstructure evolution during brazing and fracture mechanism of the joints were discussed. The results showed that a continuous reaction layer of TiO + Ni2Ti4O was formed adjacent to ZrO2 substrate, NiTi and Ni3Ti were formed at the center of brazing seam, in addition, ZrO2 substrate next to the brazing seam converted to non-stoichiometric ZrO2−x during brazing. With increasing brazing temperature, TiO decreased gradually and finally disappeared, whereas the thickness of Ni2Ti4O layer increased obviously and the reaction layer became discontinuous when the brazing temperature increased to 1350 °C and 1380 °C, besides, the morphology of Ni3Ti changed from bulk to strips and clumps. The maximum shear strength of the joint was 100.4 MPa when brazed at 1350 °C for 30 min.