INVESTIGATION ON THE REMELT TEMPERATURE OF TUNGSTEN-GRAPHITE HIGH TEMPERATURE BRAZED JOINT

The remelt temperature of the tungsten-graphite brazed joint is studied. The titanium-base filler alloy, e.g, Ti-10%Ta, is used. The temperature of brazing in vaccum is in the range of 1600~1900℃. The remelt temperature of the brazed joint is 2500~3000℃. This paper discusses the effect of brazing time, brazing temperature, brazing gap and diffusion treatment on the remelt temperature of the brazed joint. Results show that both the diffusion treatment and the brazing gap affect strongly on the remelt temperature. The mechanism of high remelt temperaiure brazed joint is thoroughly discussed. Theoretical and practical study show that reaction between graphite and titanium takes place during brazing, forming TiC phase of high melting point. Simultaneously, the composition of the rest part in the brazed joint is changed and is different from that of the original brazing filler metal:tungsten is dissolved, tantalum is increased, etc. The composition of the brazed joint is then made up of the TiC phase of high melting point and the refractory alloy of Ti-Ta-W. Thus by applying appropriate brazing technique, a joint of high remelt temperature(2500~3000℃) is got.