Magnetization and self-sharpening mechanism of polymerized diamond abrasive based on magnetorheological polishing technology

In magnetorheological polishing (MRP), the abrasive grains are confined in a semi-fixed mode by the chain strings formed by the magnetorheological particles to achieve the polishing of workpiece surfaces. The force of the abrasive particles on the workpiece comes from the force of the magnetic chain strings acting on the abrasives. However, the angular surface of the abrasive is generally smooth, resulting in a limited holding force on the abrasive by the magnetic chain strings. Therefore, the processing force of the abrasives on the workpiece is small, and it is easy to slip and escape from the polishing area. In this paper, the sintering method is used to prepare polymerized diamond abrasive(PD) with microstructures on the surface, to increase the surface area of the abrasive and to improve the control force of the magnetic chain string on the abrasive. The prepared PD has a particle size of about 25.7 μm, with a rough surface and a large amount of 3 μm single-crystal diamond particles exposed. The MRP results show that the PD have more surface micro-cutting edges and stronger machinability than the commonly used single-crystal diamond abrasives(SCD). The material removal rate(MRR) of PD on silicon wafers and sapphire wafers was increased by 173.3 % and 122.2 %, respectively. The morphological changes of the PD were traced by scanning electron microscope(SEM), and it was found that: when processing low-hardness materials, the wear of the PD was in the form of ceramic bond wear and diamond grit dislodgement; and when processing high-hardness materials, the wear of the PD was in the form of ceramic bond breakage and PD fragmentation. When abrasive grit dislodgment occurs on the surface of the PD, the formed hole enhances the force between the PD and the magnetic chain strings. Which further enhances the holding force of the magnetic chain string on the PD, and can effectively improve the magnetorheological polishing efficiency.