Microstructure and performance of monolayer brazed grinding wheel with polycrystalline diamond grains

Abstract

Monolayer brazed grinding wheels were prepared using polycrystalline diamond grains, Ni-Cr-B-Si brazing alloy, and commercial Q235A steel with the brazing temperature 1000 °C and the holding time 5 min. The microstructure and element distribution of joint interface was studied through scanning electron microscope and energy dispersive X-ray spectroscope, respectively. Grinding performance of wheels was evaluated during grinding alumina specimen. The fracture of polycrystalline diamond grains with the embedding depth of 50 and 70 % was studied quantitatively. The results show that good joint interface was formed among polycrystalline diamond grains, Ni-Cr-B-Si brazing alloy, and Q235A steel through element diffusion and chemical reaction during brazing. Chemical resultants Cr3C2 and Cr7C3 formed within joint interface between polycrystalline diamond grain and Ni-Cr-B-Si brazing alloy; meanwhile, the growth of Cr3C2 has an orientation relationship with element arrangement of diamond surface. Compared with single crystal diamond grinding wheel, the polycrystalline diamond grinding wheel has exhibited evident advantages according to the grinding force and force ration (tangential grinding force Ft / normal grinding force Fn). The Fn and Ft is 21.69 and 7.23 N with the expositing high of 50 % and 5.16 and 1.72 N with the expositing high of 70 % respectively, when polycrystalline diamond grain fracture takes place. The failure mechanism of brazed polycrystalline diamond grains grinding wheel is diamond fracture.