Effects of machining gap on the surface integrity in CBN spherical magnetic abrasives grinding of ZrO2 ceramic

Due to the high hardness and brittleness of zirconia ceramic (ZrO2), it is difficult to generate a good surface integrity by traditional grinding. The surface quality of ZrO2 can be greatly improved by magnetic abrasive finishing (MAF) with spherical CBN/Fe-based magnetic abrasive particles (MAPs) prepared by gas atomization. In this study, it was found that the difference of machining gap in MAF would seriously affect the surface integrity of ZrO2. The grinding pressure of CBN MAPs on ZrO2 under different machining gaps was analyzed theoretically. The surface morphology, surface roughness Ra and material removal amount MR, grinding pressure, surface temperature and residual stress, subsurface damage and the morphology of MAPs adsorbed by magnetic pole after grinding were studied under different machining gaps (3 mm to 1 mm). The results show that when the machining gap is large, the grinding pressure is small, the number of MAPs involved in grinding is small, and the surface integrity of ZrO2 do not change significantly. When the machining gap is small and the grinding pressure is too large, a large number of MAPs are extruded from the machining area, the magnetic abrasive brush is changed from flexible to rigid, and the ceramic surface is mainly removed by brittleness. After grinding, many cracks and pits are generated on the ceramic surface, and cracks are also produced on the subsurface, which destroys the surface integrity of the workpiece. Under the appropriate machining gap, it can not only ensure that the grinding pressure is large, but also make the ZrO2 surface mainly plastic removal, and finally obtain the best surface integrity. The optimal machining gap in this experiment is 2 mm.