Abstract: Mono-layer diamond drill bit was fabricated by high temperature brazing.The performance of brazed drill bit was compared with the electro-plated diamond drill bit in the hole drilling of silicate glass.It was found that the sharpness and the tool life of the brazed drill bit are superior to the electro-plated one due to the higher diamond grit protrusion and cohesion between diamond and filler alloy.By observation of optical microscope, scanning electron microscope, energy dispersive X-ray analysis and X-ray diffraction analysis, the microstructure and the composition of the interfaces on steel substrate-filler alloy-diamond were investigated.The diffusion of Ni and Cr from filler alloy into steel substrate was found.Reaction layers in filler alloy and diamond were identified respectively.Main phases in filler alloy reaction layer are Cr₃C₂ and Cr₇C₃, which are the reaction products of the diffusion carbon and Cr in the filler alloy.The reaction layer in diamond may be induced by the penetration of Cr into the dislocation core of graphitized diamond and formation of Cr₃C₂.