Interfacial microstructure and mechanical properties of joints between ZrO2 ceramic and 316 stainless steel brazed using Ag–Cu–In–Ti filler

An active Ag-based filler containing the melting point depressant of In was used for brazing ZrO2 ceramic with 316 stainless steel (SS) at relatively low brazing temperatures. The brazing feasibility to obtain a robust joint was investigated via changing brazing temperatures from 740 to 820 °C with a holding time of 10–30 min. The typical microstructure of the ZrO2/316SS joint was ZrO2/TiO/Cu2Ti4O + Ag(s, s) + Cu(s, s)/Ag(s, s) + Cu(s, s) + Cu(Ti, In) + FeTi + Cu(Ti, Fe)/316SS. The type of reaction products primarily depended on the brazing temperature, and the TiO phase appeared only at 780 and 800 °C, while the FeTi formed at temperatures higher than 760 °C. Meanwhile, the blocky Cu(Ti, In) and Cu(Ti, Fe) compounds were gradually replaced by the FeTi phase due to the enhanced affinity of Ti and Fe in the liquid alloy. The maximum shear strength reached 308 MPa at 780°C-20 min, and the typical fracture occurred at the Ag-based solid solution and reaction bilayer bordering the ZrO2 ceramic. Notably, a shear strength of above 270 MPa was obtained at wide temperatures from 760 to 820 °C, higher than ZrO2/SS brazed joints using other Ag-based fillers.