Microstructure characteristics of CBN/steel joints brazed with TiB 2 modified active filler

The joint of cubic boron nitride (CBN) grits to 0·45%C steel were obtained by using TiB₂ modified Ag–Cu–Ti active filler at the brazing temperature of 920°C for the holding time of 5 min. The microstructure characteristics of the brazing interface were detected by means of optical microscope, scanning electron microscope, energy dispersion spectrometer, X-ray diffraction and microhardness measuring equipment as well. It has been found that the microstructure of Ag–Cu–Ti filler layer is significantly refined by TiB₂ particles. The almost well proportioned distribution of TiB₂ particles in the filler layer is realised. Negative influence of TiB₂ particles has not occurred on the chemical reaction of CBN particles and the filler at elevated temperatures. Reliable joining of CBN grits to 0·45%C steel is accomplished dependent on the resultant reaction products at the brazing interface.