Effect of brazing temperature on microstructure and properties of 1Cr18Ni9Ti stainless steel brazed by amorphous BNi-2 filler

1Cr18Ni9Ti stainless steel was successfully brazed with BNi-2 amorphous filler. The interfacial microstructure of brazed joints at different brazing temperatures were characterised and analysed by scanning electron microscope and energy dispersive spectrometer, and the shear strength of brazed joints were tested. The effect of brazing temperatures on the interfacial microstructure and mechanical properties of the joints was investigated. The results showed that the interfacial microstructure of brazed joints could be divided into three regions from the brazing seam centre to the base material, when the brazing temperature was 1050 ℃, the brazing seam region was mainly Ni-based solid solutions + Cr-B phases; the diffusion region was distributed with Fe-Ni solid solution and fine strips of σ-FeCr phase; and in the intergranular infiltration region, the austenite grain boundaries were distributed with the σ-FeCr phases and the Cr-B phases. As the brazing temperature increased, the diffusion rate of B element was accelerated and the intergranular infiltration of Cr-B phases was intensified; the massive Cr-B phases in the centre of the braze were gradually reduced until they disappeared at 1150 ℃, and the microstructure of the braze area was homogenised. Under the effect of temperature, the width of the brazed joints showed a tendency to decrease and then increase. And the shear strength of the joints showed a tendency of increasing and then decreasing; the maximum shear strength appeared at 1050 ℃, about 265 MPa; and the fracture form of the joints was mainly dominated by ductile fracture. Using the Arrhenius equation the diffusion activation energy of the B atom was obtained as 8.18 × 10⁴ × n J/mol, with n being the time index.