Microstructure and mechanical properties of 316L stainless steel joints brazed by BNi-7 alloyed with different Cu content

Abstract

New Ni-Cr-P-Cu brazing alloys were produced in a vacuum melting furnace by adding different amount of Cu content to traditional Cu-free BNi-7 brazing alloy. 316L stainless steel was brazed with the new brazing alloy and compared with that of traditional BNi-7 brazing alloy. The physical characteristics of these brazing alloys were analyzed by DSC (differential scanning calorimetry). The microstructures of the brazing alloys and brazed joints were investigated by SEM (scanning electron microscopy) and EDS (energy-dispersive spectrometer). The shear strength and hardness of the brazed joints were also studied. The results showed that the liquidus temperature of brazing alloys decreased with the increasing Cu content. There existed two phases (primary phase (ductile α-Ni) and eutectic phase (brittle Ni3P-Ni)) in the brazing alloy and in the middle of the brazed joints. The amount of brittle phases decreased with the increasing Cu content. The shear strength at room temperature of the new brazed joint was 118 MPa for BNi-7 alloyed with 9 wt.% Cu, which was higher than that of the traditional BNi-7 brazing alloy that exhibited a shear strength of 96 MPa.