Effect of Ti content in composite filler on interfacial microstructure and joining property of Si₃N₄ brazed joint

The Si₃N₄ ceramic was brazed using AgCu+Ti+nano-Si₃N₄ composite filler(AgCuC) with different Ti contentat 900 ℃ for 10 min. The interfacial microstructure and the property of brazed joints were investigated in detail. The results showed that the typical interfacial microstructure of brazed joint was Si₃N₄/TiN+Ti₅Si₃/Ag(s,s)+Cu(s,s)+TiNP+Ti₅Si₃P/TiN+Ti₅Si₃/Si₃N₄. As the Ti content increased, the amount of aggregated nano-Si₃N₄ particles in the brazing joint decreased, while the thickness of reaction layer adjacent to substrate gradually increased and then remained unchanged. An composite-like interfacial microstructure was formed in the brazing joint when Ti content was beyond 4wt.%.However, when the Ti content further increased to 10%, a small amount of Ti-Cu intermetallic compounds was formed in brazing seam. The shear strength of brazed joints increased firstly and then decreased with the increase of Ti content.And when the Ti content was 6%, the shear strength reached a maximum value of 75 MPa.