BRAZING OF GRAPHITE AND CARBON COMPOSITES USING THIN FILM METALLIZATION

BRAZING GRAPHITE TO GRAPHITE OR TO OTHER MATERIALS IS DIFFICULT SINCE GRAPHITE IS NOT READILY WET BY MOST CONVENTIONAL BRAZE FILLER METALS. BECAUSE THE BONDING MECHANISM DEPENDS ON CARBIDE FORMATION, THE FILLER METALS USED FOR JOINING GRAPHITE TO GRAPHITE OR OTHER METALS MUST CONTAIN AN ELEMENT THAT HAS A STRONG TENDENCY TO FORM CARBIDES WITH THE GRAPHITE. THIS PROJECT INVOLVES BRAZING GRAPHITE AND CARBON/CARBON COMPOSITES. IT IS BASED ON THE SPUTTER DEPOSITION OF A THIN FILM REACTIVE METAL LAYER ON THE GRAPHITE PRIOR TO THE BRAZING. THE REACTIVE METAL LAYERWILL CONTAIN A METAL WITH A STRONG TENDENCY TO FORM A CARBIDE ON REACTING WITH THE GRAPHITE, SUCH AS TITANIUM, ZIRCONIUM, YTTRIUM, CHROMIUM, ETC. THIS THIN FILM METALLIZING OF GRAPHITE AND CARBON/CARBON COMPOSITES WILL IMPROVE WETTING AND BONDING OF THE BRAZE FILLER METAL TO THEGRAPHITE AT LOWER TEMPERATURES. IT ALSO WILL PERMIT THE USE OF STANDARD BRAZE FILLER METALS IN THE FORM OF FOIL, WIRE OR PASTE INSTEAD OF THE TAILORED, HIGH TEMPERATURE ALLOYS USED PREVIOUSLY.