Evaluation of Low-temperature Amorphous Foils for Brazing Titanium and Ceramics

摘要

New brazing filler metals in the form of amorphous foils 50 microns thick, and 75 mm wide, were evaluated for vacuum brazing of titanium alloys, graphite, and ceramics. The following amorphous foils were tested: (a) TiBraze200 (Ti-20Zr-20Cu-20Ni wt.%), having the melting range 845-863°C (1553-1585℉), (b) TiBraze590 (Zr-17Ti-20Ni-lHf wt.%), having the melting range 796-813°C (1465-1495℉), and (c) TiBraze800 (Zr-14.7Ti-12.6Ni-7Cu-1Hf wt.%) having the melting range 772-786°C (1422-1447℉). Shear strength of brazed joints of CP titanium and Ti-6Al-4V alloy and microstructures of joints studied after brazing at different temperatures are reported. Brazing temperatures of titanium joints with amorphous foils are significantly lower than that of standard filler metal AWS BTi-l (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 that 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 tested amorphous foils provided good quality of brazed samples of fin-plate titanium heat exchangers and honeycomb panels.