Papers by Author: Jin Hui 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: Ni-coated diamond grits are widely used in resin-bonding diamond tools for that nickel coating could not only increase the surface roughness, but also improve retention of the diamond in the bond. However coating nickel on diamond surface is too expensive for the high price of metal nickel. In order to obtain cost-effective coating, barrel-plating method was used to coat nickel-iron alloy on the diamond surface in this paper. Nickel-iron alloy coating with iron content of 13.62~17.25wt% has been obtained and the iron content in the alloy coating can be adjusted by the content of Fe2+ in the electrolyte. Compared with the uncoated-diamond, the compressive fracture strength (CFS) of coated diamond tested by single grit method has a distinct increase and it becomes higher as the iron content increases in the coating. The coating possesses ferromagnetism and the magnetic intensity of alloy coating with high iron content is larger than that with low iron content.