Joining of silicon nitride with a titanium foil interlayer

This work focuses on various aspects of diffusion bonding of Ti-foil interlayer during the self-joining of Si3N4. Si3N4/Ti-foil/Si3N4 combinations were hot-pressed at temperatures ranging from 1200 to 1500 degreesC with different holding times and surface roughnesses. The microstructural characterization of the resulting interfaces was carried out by SEM, EPMA, and X-ray diffraction. Si3N4 could not be bonded to Ti at temperatures lower than 1400 degreesC. Successful joining occurred at higher temperatures by the formation of a reactive interface on the metal side of the joint. EPMA and X-ray diffraction confirmed the presence of Ti5Si3, TiSi, and TiN at the interface. Thicker interfaces were obtained for polished samples compared to those produced from as-ground samples and both interfaces grew in a parabolic fashion. Joint strength was obtained by four-point bending and a maximum joint strength of 147 MPa was achieved in samples hot-pressed at 1500 degreesC for 120 min. Joints produced at joining temperatures greater than 1450 degreesC gave an average bend strength of more than 100 MPa. (C) 2002 Published by Elsevier Science B.V.