High-Frequency Induction Brazing of Al2O3 Ceramics With SiO2-Na2O-K2O-CaO Glass Filler Based on Graphite Heat Transfer Medium

A SiO ₂ -Na ₂ O-K ₂ O-CaO glass filler developed with which the brazing of Al ₂ O ₃ ceramics was achieved through the high-frequency heating using the graphite as heat conduction in this study. The effects of heating time (110 ~ 140 s) and heating current (130 ~ 170 A) on the microstructure and mechanical properties of the joint were systematically investigated. As thermal input increased, the glass filler exhibited greater fluidity, which initially enhanced shear strength before causing a subsequent decrease. Concurrently, both the amount and size of porosity at the joint were reduced, resulting in a smoother fracture surface. The maximum shear strength of 18.5 MPa, was obtained at a heating time of 130 s and a heating current of 150 A. The excessive heating (140 s and 150 A) caused the glass filler overflow and the interfacial crack formation, reducing strength to a minimum of 5.0 MPa. This study provides significant insights for the development of rapid and efficient bonding of ceramic materials.