High-temperature brazing for reliable tungsten–CFC joints

Joining of engineering ceramics

“…332 While a 99Cu-1Cr alloy has shown promise for brazing, 332 higher temperature brazes with melting temperatures .1200uC which enable the higher temperature capabilities of both tungsten and CFCs in vacuum to be exploited have thus far failed to produce joints of suitable quality. 332 Strategies suggested for joining SiC/SiC composites include coating the surfaces with silicone resin followed by heating at temperatures between 900 and 1200uC in an argon or nitrogen flux under little or no pressure, 324,333 glass-ceramic joining and coating, 334,335 filling the joints with polyhydridomethylsiloxane and SiC, Al and Al 2 O 3 powders singly and in combination and then pyrolysing, 326 the use of tape cast ribbons of Si/TiC powders as a filler material, 326 and a diffusion bonding-based approach using titanium foils and physically vapour deposited titanium coatings. 336 The strength of some of these joints clearly needs to be improved, 325 and so there is a need both to continue to develop each of the various currently competing technologies to ensure that the needs of future fusion projects are met, as well as to develop new SiC/SiC joining technologies, as Henager et al have recently noted.…”