Microstructure and mechanical properties of ZrO₂ ceramic and Kovar brazed joints

Brazing of ZrO₂ ceramic to Kovar alloy was successfully realized by using self-developed Ag-Cu-TiH₂ filler powder at the 825~960°C for 1~60 min. Interface microstructures were investigated by scanning electron microscopy, X-ray diffraction and EDS energy spectrum. The results showed that the typical interface microstructure of brazed joints from Kovar side to ZrO₂ ceramic side could be expressed as Kovar/Ag (s. s) + Cu (s. s) +TiFe₂/TiNi₃ + TiFe₂ + Ti-Fe-Ni/Ag (s. s) + Cu (s. s) + TiFe₂/Cu₂Ti₄O/TiO + Zr_xO_y/ZrO₂. The maximum shear strength of the joints was 134 MPa, which was achieved when the brazing temperature was 875°C and holding time was 10 min. The brittle fracture took place on the TiC interface. When the brazing temperature and holding time changed, the brazed joints weakened and the shear strength decreased.