Microstructural evolution and mechanical properties of Ni-based superalloy joints brazed using a ternary Ni-W-B amorphous brazing filler metal

A family of novel Ni-based amorphous alloys was developed with high W concentration (up to 39 wt%) in Ni-W-B system. The crystallization and melting behaviors of the typical Ni-based amorphous alloys were evaluated in detail. The optimal composition of Ni75W5B20 (at%) with the high W concentration of 16.6 wt% and the near-eutectic melting behavior (liquidus temperature of 1393 K) in the Ni-W-B system was screened out for brazing joint of GH3230 [J Aeronaut. Mater., 36 (2016) 27–39]. The effects of the brazing temperature from 1413 K to 1473 K on the microstructural evolution and mechanical properties of the GH3230/Ni75W5B20/GH3230 joints were studied. The homogeneous brazed seam consisting of single γ-(Ni,W) solid solution phase can be obtained under the optimal brazing conditions with sufficient diffusion of B into base metal to form the dispersed needle-/net-like Cr-rich borides. The high tensile strength of the optimal brazed joints can be obtained up to 860 MPa at room temperature and 139 MPa at 1253 K (99% and 92% of that of the base GH3230 alloy, respectively). The relationship between fracture behaviors and microstructure in the joints were revealed.