Effect of brazing temperature on microstructure and mechanical properties of Si₃N₄/Si₃N₄ joints brazed with Ag–Cu–Ti + Mo composite filler

摘要

Mo particles have been introduced into Ag–Cu–Ti brazing alloy for the joining of Si₃N₄ ceramic. Effect of brazing temperature on microstructure and mechanical properties of the joints were investigated. The result shows that a continuous reaction layer which is composed of TiN and Ti₅Si₃ was formed at the Si₃N₄/braze interface. The central part of the joint was composed of Ag-based solid solution, Cu-based solid solution, Mo particles, and Cu–Ti intermetallic compounds. By increasing the brazing temperature, both the thickness of the reaction layer and amount of Cu–Ti intermetallic compounds in the joint increased, being beneficial for the joint strength. Whereas, the reaction between Ti and Si₃N₄ ceramic proceeded excessively and more Cu–Ti intermetallic compounds were precipitated in the joint while elevating the brazing temperature to 950 °C, leading to deterioration of the bending strength. The maximal bending strength reached 429.4 MPa at 900 °C for 5 min when the Si₃N₄ ceramic was brazed with Ag–Cu–Ti + Mo composite filler.