Brazing SiO2-BN diphase ceramic with Nb by using multilayer Ti-Ni composite foils.

The multilayer Ti and Ni foils were designed to braze SiO 2 -BN diphase ceramic with Nb at 1140 °C for 5min. The interfacial microstructure was examined using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), transmission electron microscope (TEM) and X-ray diffraction (XRD) methods, respectively. Experimental results and thermodynamical calculations showed that the interfacial microstructures between Nb and SiO 2 -BN ceramic were (βTi,Nb)-TiNi eutectic structure/TiNi + TiNi 3 /TiN + Ti 3 O 5 + TiB 2 + Ti 5 Si 3 . The effects of the Ti content in the Ti-Ni braze alloy on the microstructures of the joints were investigated. With the increase of the Ti content, less Ni 3 Nb formed in the joint and TiNi 3 phase successfully turned into TiNi and Ti 2 Ni. The effects of the Ti content in the Ti-Ni braze alloy on the shear strength of the joints showed that the optimum thickness of the TiN + Ti 3 O 5 + TiB 2 + Ti 5 Si 3 reaction area was about 13 μm and the maximum shear strength of 52 MPa was achieved when the Ti content was 45 wt.%. [ABSTRACT FROM AUTHOR]