Effect of Cr content in Ni-based amorphous filler on microstructure and shear strength of K4169 nickel-based alloy brazed joint

Three nickel-based amorphous filler materials with composition of [B-Ni9-xCrx]BSiNi (x = 0,1,2) were designed to braze K4169 superalloy according to cluster-plus-glue-atom model. The microstructure of K4169 nickel-based alloy brazed joints was examined, and the shear strength of the joint was also measured via pressure-shear tests. The brazed seam consists of gamma-Ni solid solution, Nb6Ni16Si7 and CrB phases of joint brazed with [B-Ni7Cr2]BSiNi filler. More Nb6Ni16Si7 phase formed in the brazed seam with more Cr addition in filler material, because Cr promoted the diffusion of Nb atoms from base material to brazed seam. Diffusion zone was composed of needle-like Cr-Mo rich borides and blocky MC carbides (NbC, TiC). The amount of Cr-Mo rich borides went up with the enhancement of Cr content in filler material. The shear strength of joint reached 689 MPa when brazed with [B-Ni-9]BSiNi filler, followed by 562 MPa with [B-Ni8Cr1]BSiNi filler and 450 MPa with [B-Ni7Cr2]BSiNi filler. In addition, Cr-Mo rich borides and continuous precipitation (Nb6Ni16Si7 and CrB) exhibited low resistance to crack, resulting in the degradation of joint strength.

Automated summary

Three nickel-based amorphous filler materials were designed for brazing K4169 superalloy, and the microstructure and shear strength of the brazed joints were examined. The addition of more Cr in the filler material promoted the diffusion of Nb atoms, resulting in increased formation of Nb6Ni16Si7 phase in the brazed seam. The shear strength of the joint varied with different filler materials, with the presence of Cr-Mo rich borides and continuous precipitation exhibiting low resistance to crack.