Vacuum brazing of super-Ni/NiCr laminated composite to Cr18–Ni8 steel with NiCrP filler metal

Vacuum brazing of super-Ni/NiCr laminated composite and Cr18–Ni8 steel was performed using NiCrP filler metal. Microstructure, elemental distribution, microhardness and shear strength were investigated by means of scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and electromechanical universal testing machine. An excellent joint was obtained at 1040 °C for 20 min and the shear strength was as high as 137 MPa. The brazed region was divided into solid solution zone and eutectic zone. Elemental distribution indicated that P mainly concentrated in the eutectic zone in the form of Ni3P. Ni2Cr particles precipitated in NiCr base layer under the influence of thermal cycling.

► Vacuum brazing of super-Ni/NiCr laminated composite and Cr18–Ni8 steel with NiCrP filler was performed at 940, 980 and 1040 °C for 20 min.
► Excellent joint was obtained at 1040 °C for 20 min and the shear strength was 137 MPa.
► Brazed region consisted of γ-Ni solid solution and eutectic of γ-Ni(P) and Ni3P.
► There was Ni2Cr particles precipitated in NiCr base layer with the influence of heating cycle.
► Due to the same matrix of filler metal and super-Ni/NiCr laminated composite, interfacial region between them is not clearly observed.