Microstructure of high temperature brazing cubic boron hitride grits

In order to develop new generation monolayer brazed CBN (cubic boron nitride) grinding wheels, Ag-Cu-Ti active filler alloy was utilized to braze CBN grits to steel substrate in vacuum furnace. The microstructure and the element distribution of the joining interface, as well the topography and the phase structure of the compounds on the surface of brazed CBN grits, were analyzed by scanning electron microscope, energy dispersion spectrometer and X-ray diffraction. The results show that Ti in the filler alloy transferred preferentially to the surface of the CBN grit to form a layer of needle-like Ti-nitride and Ti-boride compounds by the interaction reaction between Ti and N and B at high temperature. Thus, the chemical metallurgic joining has been formed in the interface between CBN grits and Ag-Cu-Ti alloys. Finally comparative grinding tests were performed with monolayer brazed CBN grinding wheels and electroplated ones, and the result indicates that the brazed wheels showed higher joining strength to the CBN grits than the latter.