Microstructure and shear strength of Mo–Cu/Cr18-Ni8 brazing joint in vacuum

High density Mo–Cu composite and Cr18-Ni8 stainless steel were brazed with Ag–Cu filler metal in vacuum of 10−5 Pa. The microstructure characteristics of Mo–Cu/Cr18-Ni8 brazed joint were investigated by field-emission scanning electron microscope (FESEM) with energy dispersive spectrometer (EDS) and shear strength was measured by shearing test. The results indicated that a Mo–Cu/Cr18-Ni8 joint with shear strength of 125 MPa was obtained at 940 °C for 20 min. There were Ag–Cu eutectic and Cu-rich phase without brittle intermetallic compounds formed in the joint. The shear fracture exhibited plastic feature with shear dimple and fracture located at the interface between braze seam and Cr18-Ni8 stainless steel.

► Mo–Cu/Cr18-Ni8 joint with 125 MPa shear strength was obtained at 940 °C for 20 min.
► There are Ag–Cu eutectic and Cu–rich phase in joint without brittle compounds.
► Plastic feature with shear dimple was exhibited after the shearing of joint.
► Fracture located at the interface between braze seam and Cr18-Ni8 steel.