Research On Ti-Zr-Cu-B Amorphous Brazing Filler Metal For Brazing Si₃N₄ Ceramics

On the basis of studying activity brazing of Si3N4 ceramics in this paper, three kinds of brazing metal CuTi30Zr25B0.2, CuTi35Zr25B0.2 and CuTi40Zr25B0.2 were designed with trace B element. And they were made into rapidly-cooled foil belt filler metal by single-roll rapidly-cooled equipment, studying the melting characteristics, structure and composition distribution with using DTA, XRD and EDS and other micro-analytical tools. Si3N4 ceramics were brazed with the prepared amorphous brazing metal to explore the processing properties and mechanical properties of joint. The comparison analysis was carried out between the amorphous and the crystalline brazing metal with the same composition. The interface microstructure, interfacial reaction and the reaction layer which have effect on mechanical properties of joint were explored by SEM, EDS and so on. The results showed that: compared to the crystalline brazing metal with the same composition, the above three kinds of apidly-cooled foil belt filler metal have lower melting temperature, even narrower melting temperature interval, and their structure are all amorphous. The content of active element Ti in brazing alloy and the brazing technics parameters all have influence on wettability on Si3N4 ceramics and joint strength, embodying mainly through interface reaction, the structure and the thickness of the reaction layer. Under the same experimental condition, the wettability on Si3N4 ceramics and joint strength of amorphous brazing metal are all stronger than the crystalline one with the same composition. The joint exhibited a highest room temperature strength of 191.5MPa, which was brazed with CuTi40Zr25B0.2 amorphous brazing metal at 1323K for 30min with a pressure of 0.012MPa. The element Ti is more active than Zr, reacting with the Si3N4 ceramics firstly in Ti-Zr-Cu-B active alloy. The interface reaction layer in the joint brazed with CuTi40Zr25B0.2 amorphous brazing metal is made up of TiN abut on the ceramics and the Zr-Si, Ti-Si compounds. When the test temperature was 473K, the joint had a highest high temperature strength of 165.5MPa, then the high temperature strength of joint was down after test temperature 573K, and reduced rapidly beyond 673K.