Evaluation of Brazed Silicon Nitride Joints: Microstructure and Mechanical Properties

Sintered Si3N4 has been bonded to itself and to AISI 316 steel by the active‐metal brazing route. A commercial Ag‐35Cu‐1.6Ti filler has been used with joining taking place during a 30 min hold at 850°C under vacuum. Si3N4/ Si3N4 joints have been produced with strength distribution (average bend strength = 773.5 MPa, Weibull modulus = 11.2) similar to that of the monolithic ceramic. Direct brazing of the Si3N4 to AISI 316 steel was unsuccessful. However, reliably strong (bend strength of 250–400 MPa) ceramic/ steel joints with 20 × 20 mm2 cross sections were fabricated by using Cu, Mo, or Nb interlayers. The most potent inter‐layer used in this work was Mo, whose coefficient of thermal expansion matches best that of the ceramic.