Microstructure and shear strength of high-temperature brazed joint of Super-Ni/NiCr laminated composite using Ni-Cr-Si-B filler metal

Super-Ni/NiCr laminated composite and Cr18-Ni8 steel were brazed with Ni-Cr-Si-B high-temperature brazing filler metal. The microstructure, phase constitution, shear strength and fracture morphology were analyzed. The brazed region consisted of γ-Ni solid solution,Ni₃B,CrB and Ni₃Si. The microhardness fluctuated across the brazed region. The microhardness of γ-Ni substrate was 450 MPa and that of Ni₃B was 650 MPa. The shear strength of the joint increased to 158 MPa as the brazing temperature increased to 1 120℃. The fracture surface displayed brittle features with some shearing dimples. Ni₃B interface formed between the super-Ni and brazed region. The joint fractured through the Ni₃B interface.