Tag Archives: graphite

Brazing of titanium, ceramics, and graphite using new low-temperature Ti- and Zr-based amorphous foils

Applications of new brazing filler metals in the form of amorphous foils 50 microns thick, and 75 mm wide for vacuum brazing of titanium alloys, graphite, and ceramics are discussed in the paper. Brazed joints were evaluated by testing strength, microstructures, and sometimes phase compositions of base and filler metal interfaces. The following amorphous foils were tested: (a) TiBraze®200 (Ti-20Zr-20Cu-20Ni wt.%) with the melting range of 845-863°C (1553-1585°F), (b) TiBraze®590 (Zr-17Ti-20Ni-1Hf wt.%) with the melting range of 796-813°C (1465-1495°F), and (c) TiBraze®800 (Zr-14.7Ti-12.6Ni-7Cu-1Hf wt.%) with the melting range of 772-786°C (1422-1447°F).
Shear strength of brazed joints of CP titanium and Ti-6Al-4V alloy with copper, stainless steel 304, and Ni-plated carbon steel are reported, as well as microstructures of joints studied after brazing at different temperatures. Brazing temperatures of titanium joints with amorphous foils are significantly lower than that of standard filler metal AWS BTi-1 (Ticuni®). Brazing of titanium-to-ceramics and graphite with new foils should be done at temperatures greater by 50-60°C than that of brazing titanium-to-titanium. If compared to traditional active brazing filler metals which do not spread on ceramic surfaces, the tested Ti- and Zr-based amorphous foils revealed excellent wetting, and sometimes spreading, along ceramic surfaces of alumina and boron nitride, as well as graphite. Also, all samples of fin-plate titanium heat exchangers and honeycomb panels brazed with amorphous foils displayed good quality of the brazed joints.