Study On Low Melting Point And High Strength Vitrified Bond Superhard Grinding Tools

Sintering temperature of vitrified bond superhard grinding tools is high and the vitrified bond contains alkali oxide that can decrease melting point of the bond commonly. Both of these can damage superhard grinding grains. To settle this problem three aspects research were carried out. Firstly, a vitrified bond whose melting point is low was prepared. Secondly, a protective film was coated on the surface of the grains at low temperature. At last hot pressing experiments was carried out.Raw materials for preparing the bond were mainly clay, boric glass, lead glass and zinc oxide. At high temperature(above 850℃) the bond was glassy and had good soakage to superhard grains. When the ratio of corundum and the bond was 6.5:3.5, the bending strength at sintering temperature of 850℃ for 7 minutes was 125.7MPa.By means of vacuum slow vapor deposition, oxide directly and sol-gel techniques Al, Si, Ti, TiO2 or Al2O3 films were coated on the surface of the grains. The structure characteristics of the interface and the effect of the coating of the grains were investigated by means of X-ray diffraction and difference thermal analysis. The results showed that, AlN existed between aluminum coating and cBN grains, SiC existed between silicon coating and diamond grains, no resultant existed between silicon coating and cBN grains, TiSi2 existed between silicon coating and Ti-coated diamond grains.The hot pressing and the bending strength experiments results showed that all coatings except for aluminum coating could increase the bending strength of the grinding tools. Aluminum coating could react with the bond and damage the wet structure. Alumina coating could increase the bending strength of the tools to 114.8%.