Diffusion bonding of silicon nitride to titanium

Si3N4/Ti and Si3N4/Ti/Si3N4 combinations were joined by solid state diffusion bonding using hot pressing at temperatures ranging from 1200 to 1500 degreesC. The microstructure of the resulting interfaces was characterised by scanning electron microscopy electron probe microanalysis, and XRD. Si3N4/Ti samples hot pressed at temperatures less than 1400 degreesC could not be bonded. However, at 1400 degreesC bonding of single joints occurred, although the samples debonded during SEM preparation. Hot pressing at 1500 degreesC resulted in effective joining by the formation of a reactive interface. For Si3N4/Ti/Si3N4 sandwich samples hot pressed at 1400 and 1500 degreesC, successful joining of Si3N4 to Ti occurred by the formation of an interface on the Ti side. The surface roughness of the joint materials plays an important role, affecting the thickness of the reaction products. The interfaces grew in a parabolic fashion with the formation of various titanium silicides (Ti5Si3 and TiSi) as well as titanium nitride (TiN).