Induction Brazing of Alumina and Zirconia with Various Metals

Conventionally brazed metal-ceramic joints are produced in vacuum furnaces. Since furnace brazing is characterized by high losses and low efficiency, the induction brazing is studied as an energy-efficient alternative for brazing of metals and ceramics. A great advantage of induction heating is the direct heating of components, which is highly efficient and leads to significantly reduced processing times. In comparison to furnace brazing processes, this results in a completely altered process management. Based on selected results, this paper discusses the influence of process management on joint properties. Using a commercially available active brazing filler metal (Ag-26,5Cu-3Ti), joints of alumina and zirconia were brazed with different metals (CrNi 18 10 steel, FeNi42 and FeNiCo 29 18). Brazing was carried out in a furnace, as well as by induction with varying temperature-time curves. Microstructure and mechanical strength (4-pont bending test) of the joints are compared for both processes. Depending on the type of ceramic, the bending strengths can be influenced by different process parameters. An adjustment of these parameters leads to equivalent bending strengths of induction brazed joints compared to furnace brazed ones. Due to the short process times, induction brazed joints exhibit less filler metal evaporation and a smaller amount of brittle phases. Therefore, higher mechanical strengths are expected with induction brazing when using real components (geometry dependence of bending strength).