Microstructure and properties of ceramic/stainless steel joint with Ni foam interlayer

Al₂O₃ ceramic and 1Cr18Ni9Ti stainless steel were brazed with or without Ni foam interlayer at the temperature of 850°C for 60 min at vacuum. The microstructure of the joint was investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), besides shearing tests were used to test the mechanical properties of the joints. The experimental results show that the average shear strength of the joint without Ni foam interlayer is 7.7 MPa, and the fracture occurs in the ceramic. While Ni foam interlayer is used, the average shear strength of the joint is up to 101.7 MPa, and the fracture is located at the interface of ceramic and Ni foam interlayer. Without Ni foam, Ti is mainly distributed at the interface of ceramic and Ag-Cu-Ti and the interface of steel and Ag-Cu-Ti. With Ni foam, element Ti is distributed at the interlayer zone where TiNi₃ is formed during the brazing process, besides, the distribution of Ag, Cu, Ti element is more uniform.