Silicon nitride nickel joints through diffusion bonding

Diffusion bonding of Si3N4 to Ni under low vacuum conditions was studied. Thr joint interfaces were analysed in terms of microstructure, elemental diffusion, chemical reactions and mechanical properties. The mechanisms involved in the bonding process were investigated and related to the characteristics of the starting material, to the adopted experimental conditions and to the joint fracture strength. Interdiffusion and intrinsic diffusion coefficients of the elements involved (Ni, Si) in the diffusion process and the relative activation energies were calculated. The expected formation of brittle silicides at the interface was avoided through the use of relatively short soaking times and small applied pressures. A high flexural strength value was obtained (maximum value 473 MPa).