## 1 Introduction  
GH4169 is a precipitation-strengthened nickel-base superalloy with excellent fatigue resistance, radiation resistance, oxidation resistance, and corrosion resistance below 650 \({}^{\circ}\)C [1; 2; 3]. It is widely used in aerospace engines, nuclear reactors, petroleum pumps, and extrusion models [4; 5]. During the aging process, face-centered cubic \(\gamma^{\prime}\) phase (Ni\({}_{3}\)Al, Ni\({}_{3}\)Ti, Ni\({}_{3}\)(Al, Ti)) and metastable body-centered tetragonal \(\gamma^{\prime\prime}\) phase (Ni\({}_{3}\)Nb) would form in GH4169 alloy. The high strength of GH4169 is caused by the precipitation strengthening of the \(\gamma^{\prime\prime}\) phase [6; 7].  
GH4169 nickel-base alloys are costly. Defective parts are often repaired by welding rather than being replaced. For example, some turbine engine components (e.g., racks, blades) may be repaired several times during service [8; 9]. The welding of nickel-base alloys is usually difficult. Even with laser beam welding and electron beam welding, harmful intermetallic compounds inevitably form in the welding zone, which lead to the deterioration of the mechanical properties of the joints [10; 11; 12; 13; 14]. In order to solve the problems during the welding process, some researchers have tried transient liquid phase (TLP) bonding technology to join nickel-base alloys. [PERSON] et al. [15] brazed IN718 using the TLP method, in which a Ni-Si-B ternary alloy was used as the filler metal. The results showed that the mechanical properties of the joint mainly depend on the precipitation of the eutectic phase during solidification. [PERSON] et al. [16] studied TLP bonding of SAF2507 and AISI304 stainless steel usingBNi-2 amorphous foil and found that the intermetallic compounds in the joint center decreased with the prolongation of holding time at a set temperature. A joint free of intermetallic compounds was obtained at 1050 \({}^{\circ}\)C for 45 min. The TLP bonding of IN718 and IN625 nickel-base alloys using a BNi-2 interlayer was investigated by [PERSON] et al. (2017). It was suggested that the proper bonding temperature should be between 1050 and 1120 \({}^{\circ}\)C.  
At present, the welding of GH4169 nickel-base alloy is also very difficult. Solid-state solder foils are most commonly used in the welding of GH4169 alloy in industry. As for solder foils, they need to be stamped into the required shape and size during practical application. The cutting process is time-consuming, and the rate of material utilization is low. Another issue is that the intermetallic compounds in the joint center which deteriorate the shear resistance cannot be eliminated completely, which makes the quality of GH4169 weldments unstable. In order to find a new method for batch welding GH4169 with high efficiency, reliability, and low consumption, the TLP welding of GH4169 alloy was studied by using BNi-2 solder paste in this paper. The solder paste is easily extruded and is not be restricted by the shape of the bonding parts. As mentioned above, the TLP method has proved to be an effective technique for obtaining excellent nickel-based alloy joints at relatively low temperatures. The TLP bonding processes of GH4169/BNi-2/GH4169 systems were carried out at 1040-1100 \({}^{\circ}\)C for 30 min to achieve a joint with high shear strength that was free of intermetallic compounds. The effect of bonding temperature on the microstructure and mechanical properties of the GH4169 joints was investigated.