BEHAVIOUR OF BUFFER LAYER IN JOINING OF SIALON CERAMICS TO 4OCr STEEL

The buffer layer material itself may be influential to the bond strength between active brazing filler and ceramics. For Ag_(57)Cu_(38)Ti_5 filler metal, Cu or Ta is excellent buffer layer material, but Kovar or Ni-15Cr-15Co is worse. It was important to design a layer of soft buffer, such as Cu, to relax interfacial stress rather than hard buffer layer, such as Mo, to avoid stress. There is an optimum thickness range of soft buffer layer, saying h/L=0.02-0.1. It was a good solution to the interfacial stress problem to use soft/bard buffer layer to increase metal/ceramics joint strength. Finally, an idea of designing gradual materials as buffer layer between metal and ceramics was suggested.