Microstructure and properties of vacuum brazed joint between super-Ni/NiCr laminated composite and Cr18-Ni8 steel

Vacuum brazing of super-Ni/NiCr laminated composite to Cr18-Ni8 steel was performed using Ni-Cr-Si-B amorphous foil. Microstructure characteristic and shear strength of the brazed joints were investigated by scanning electron microscopy (SEM),energy-dispersive spectroscopy (EDS),microsclerometer and mechanical universal testing machine. The experimental results showed that the Ni-Cr-Si-B amorphous foil exhibited good wettability on super-Ni/NiCr laminated composite. The brazed region consisted of γ-Ni solid solution and Ni3B. Dissolution and diffusion occurred between the filler metal and super-Ni/NiCr laminated composite. An excellent bonding was obtained between them. An interface consisting of fine boride particles formed between the filler metal and Cr18-Ni8 stainless steel. The shear strength of the brazed joint reached 170MPa,and the fracture morphology displayed stepped fracture surface with some dimples and tearing feature in the brazed region.