Papers by Author: Xiang Hong Zhang

Abstract: Oxidization of diamond in the sintering process of diamond/borosilicate glass composites would result in low compressive fracture strength (CFS) of the grit and uncontrolled expansion with many irregular pores in the composites, causing low bending strength of the tools. In this paper diamond/borosilicate glass composites were prepared by cold pressing and sintering at 850 C for 120 min in air. An active element Zn was incorporated into the composites in order to resolve the above issues. The effects of Zn contents on the properties of the composites was investigated by the bending strength tests, the volume expansion rate tests, differential scanning calorimeter test (DSC), thermogravimetry (TG), X-ray diffraction analysis (XRD), and scanning electron microscope (SEM). The results showed Zn was oxidized and then converted to ZnAl2O4 and Zn2SiO4 phases during sintering. The bending strength improved and the expansion phenomenon was inhibited for the composites with various Zn additions. The maximum bending strength and minimum volume expansion rate were obtained for the composite GZ8. This Zn content resulted in a decrease of volume expansion rate from 8.57% to -20.53%, and an increase in bending strength from 28.49 MPa to 74.02 MPa compared with the composite GZ0. The CFS results of the diamond grits separated from GZ0 and GZ8 was 21N and 26N, respectively.

Abstract: The adhesion between diamond grits and the bond strongly influence the properties of diamond tools. Since diamond is covalent crystal, the high interfacial energy leads to the poor interface bonding between diamond grits and the bond. Furthermore, the sintering temperature of traditional vitrified bond is also very high because of the high refractoriness of alkalis containing in the bond, resulting in serious thermal damage to diamond grits. In this paper, a low melting point and high strength vitrified bond has been prepared mainly from borate glass, clay and lead glass. The bond is completely glassy above 850°C and the bending strength of the bond sintered at 850°C for 7 minutes is 125.7MPa with a 6.5:3.5 corundum/bond ratio. Moreover, this bond possesses good wettability with diamond abrasive from 600°C to 850°C.