| With the rapid development of science and technology, new materials are emerging and have increasing requirements for processing technology and processing quality, which results that grinding technology is progressively growing for the goal of high-speed, high-efficiency, high-precision. As one of important grinding tools, vitrified bond cubic boron nitride (cBN) abrasive, due to its excellent grinding performance and surface quality, has been widely noted. Meanwhile, glass-ceramic bond with high mechanical strength and adjustable thermal expansion coefficient can preferably meet requirements of general properties of vitrified bond for the increasing development of grinding technology. Therefore, glass-ceramic bond for high-performance cBN grinding wheel was studied.In this paper, the preparation of glass-ceramic bond and its cBN grinding wheel were systematically investigated. SiO2-Al2O3-B2O3-R2O-RO was chosen as the basic vitrified bond system, in which three different kinds of ZnO, ZrO2 and CaF2 as additives were added. The influences of different kinds of additives and their content on vitrified bonds were studied by X-raydiffraction (XRD), scanning electron microscopy (SEM) and three-point bending strength testing et al, and glass-ceramic bond with high mechanical properties was prepared; then, some experiments about formulas and preparing process of cBN abrasive were investigated and glass-ceramic bond cBN grinding wheel with excellent performances were prepared.The results indicated that adding ZnO, ZrO2 and CaF2 to the basic vitrified bond contributed to the precipitation of β-quartz. When added ZnO and ZrO2, the content of P-quartz was excessive, which resulted that the uniformity and continuity of glass phase was destroyed and had a negative impacton the bending strength of glass-ceramic bond. With the increasing of amount of CaF2, the precipitation amount of P-quartz increased accordingly and the gradual emergence of plate and columnar grains, which resulted that bending strength of glass-ceramic bonds gradually increased; When added 10wt% CaF2, bending strength of glass-ceramic bond promoted to 173 MPa, which was increased by 64% than those without CaF2, and glass-ceramic bond exhibited a high microhardness (7.49 GPa), which was conducive to improving the grinding efficiency of grinding wheels as well as the service life. Moreover, glass-ceramic bond added CaF2 had better wettability to cBN, which resulted that the bending strength of cBN abrasive was increased by 26%.The basic vitrified bond added 10 wt% CaF2 as a glass-ceramic bond, the amount of bonds, cBN particle size and preparing process had a great effect on the microstructure and properties of cBN grinding tools. When the amount of glass-ceramic bond was 60 wt%, bending strength of cBN abrasive reached the maximum,60 MPa. When cBN particle size was 140/170 mesh, the bulk density and bending strength of cBN abrasive reached 2.50 g·cm-3 and 60 MPa, respectively. When abrasive samples sintered at 680～800℃ for 2 h, the bending strength reached 44 MPa and abrasive samples sintered 760℃ for 3 h and 5 h, the bending strength reached 60 MPa and 62 MPa respectively. Therefore, the best process system was:with the bond amount of 60 wt% and cBN particle size of 140/170 mesh added, cBN abrasive sintered at 760℃ for 3 h had the bending strength of 60 MPa. |
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