Low-Temperature Transient Liquid Phase Joining of a Si₃N₄/GH3039 Dissimilar Structure: Interfacial Reaction Mechanisms and Microstructure–Property Evolution Associated with a Cu80Ti15Ni5 Interlayer

Si₃N₄ ceramic, as an important engineering material, is widely used in fields such as aerospace, mechanical electronics, and the nuclear industry. To further expand its application range, Cu80Ti15Ni5 (at.%) mixed powder is used as an intermediate layer for transient liquid phase bonding between Si₃N₄ and GH3039 nickel-based high-temperature alloy. This paper mainly studies the typical microstructure of the joints and explores the formation mechanism of the joints. The filler material generates sufficient liquid phase at 970 °C to fill the weld seam, and high-melting-point intermetallic compound (Cu,Ni)₂Ti is formed in situ in the brazing seam. Finally, isothermal solidification is completed, resulting in a joint primarily composed of Cu(ss) and (Cu,Ni)₂Ti. In addition, the microstructural changes of the joints under different bonding times were also studied, with the increase in bonding time, the interfacial reaction layer on the ceramic side thickened, and the bonding between the ceramic and the brazing seam became tighter. The shear strength of the joint initially increases and then decreases with the increase in bonding time, reaching a maximum of 71.4 MPa at 15 min, and the fracture behavior is also analyzed.