Influence of TiH{sub 2} on Interfacial Reaction Features Between Cubic Boron Nitride and Cu-Sn-Ti Active Filler Metals
Cubic boron nitride (CBN) grains are brazed by Cu-Sn-Ti filler metal in vacuum at 1223 K. Wetting behaviors, reaction layer features, and elemental distribution characteristics have been systematically investigated through scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The results show that when the TiH{sub 2} content is 5 wt pct, virtually no sharp-edged, partially coated, and uncoated CBN grains can be observed, indicating that adequate wetting could be achieved. Moreover, a continuous reaction layer with uniform thickness (1.30 μm) consisting of TiN, TiB{sub 2}, and TiB is obtained, which indicates that large numbers of TiN, TiB{sub 2}, and TiB compounds could have been formed at the interface. However, when the TiH{sub 2} content exceeds 5 wt pct, the thickness of the reaction layer is no longer significantly expanding and excessive Ti present in the matrix will lower the volume percentage of Cu{sub 3}Sn{sub 1} phase, which will reduce the bonding strength of the brazing samples. Wear tests indicate that the minimum weight loss also occurs at 5 wt pct TiH{sub 2}.