| Metal bonded diamond grinding wheels have the characteristics of high intensity, good abrasion resistance and long service life, and have been widely used in manufacturing of hard and brittle materials, such as hard alloy, stone, ceramics, glass, etal. However, metal bonded diamond grinding wheels fabricated by power metallurgy method are dense type, which lead to poor selfsharpness, and it’s easy to jam, difficult to repair the sharp plastic. As a result, the grinding efficiency was decreased. In this paper, pore structure was introduced to metal bonded diamond grinding wheel, and the porous metal bonded diamond grinding wheels were prepared. This kind of grinding wheel has the advantages of good self-sharpening, small grinding force and low grinding temperature.In this project, Cu-matrix porous diamond grinding wheels were prepared by vacuum hot pressing sintering method. The effect of different content of Sn and Zn on the mechanical properties of Cu-matrix bonding body was studied. When total content of Sn and Zn was 10%, with the increase of the content of Sn, the transverse repture strength increased from 479.85 MPa to 701.82 MPa, while rockwell hardess increased from 64.8HRB to 99.8HRB and wear resistance increased gradually. The pore-forming effect of two kinds of pore inducers was researched, and the size and distribution of pore were observed by metallographic microscope. Performance of pore induced by ammonium bicarbonate is better than stearic acid. Diamond segments with the porosity ranging form 5.6% to 39.9%, correspondingly, the transverse repture strength of diamond segments ranged from 401.9MPa to 58.7MPa. Microstructure morphology of fracture surfaces in porous diamond segments were observed by scanning electron microscope and fracture models were built respectively. When porosity is lower than 20%, the strength of the diamond segments mainly affected by the combination interface between diamond and bondind body, however, when porosity is more than 30%, the pore becomes the main factor of the diamond block strength.The diamond pre-brazing process was preliminary explorated, the transverse repture strength of diamond segments was improved using pre-brazed diamonds as abrasives. The material removal mechanism inclused ductile and brittle regime in hard brittle material grinding process was analyed theoretically, and grinding advantages of hard brittle material grinding removal in ductility region by porous metal bonded diamond grinding wheel were proposed. On the universal friction and wear testing machine, YG8 hard alloy materials were grinded, the test results showed that porous metal bonded diamond segments had good self-sharpening and low friction coefficient. When the porosity was about 20%,the grinding ratio attained the maximum. |
