AN EVALUATION OF THE PARTIAL, TRANSIENT LIQUID-PHASE BONDING OF SI3N4USING AU COATED NI-22CR FOILS

The application of the partial transient liquid phase bonding (PTLPB) process for joining silicon nitride ceramics using microdesigned Au/Ni -Cr/Au multilayer interlayers has been investigated. The influence of different bonding parameters, such as time, temperature and interlayer thickness, on the microstructure and chemistry of the ceramic-metal i nterfaces has been studied. Scanning electron microscopy and electron probe microanalysis investigations revealed that the ceramics were bon ded to the Ni-Cr foils by a thin CrN reaction product layer while the Au had alloyed to form a Ni rich solid solution. Joints with room temp erature average flexural strength of 272 MPa, were produced under opti mized bonding conditions of 4 h at 1000 degrees C. These processing co nditions resulted in joints with microstructure and strength equivalen t to those obtained by optimized diffusion bonding procedures. The eff ect of post-bonding annealing in air at 800 degrees C for 60 h on the room temperature joint strength was also assessed.