Joining mechanism in Si3N4 bonded with a Ni–Cr–B interlayer

A commercially available Ni–Cr brazing alloy foil with B infused at its surface layer was used to join silicon nitride ceramics. The joining region showed a diffusion zone at the middle of the interlayer and a reaction layer at the silicon nitride/brazing alloy interface. The reaction layer mainly consisted of CrN and BN while the diffusion layer was formed by Ni[Cr, Si] solid solution with some CrN precipitates. A reaction mechanism is proposed to explain the microstructure and phases observed in the bonding interlayer.