Research On The Mechanical Wear Of Diamond Abrasive Grit In Scratching Process

Diamond abrasive tools are widely used to machine many materials with high efficiency and precision. The wear of diamond has an important influence on the tool life and machining quality. The wear of diamond grit in the diamond abrasive tools is found to have great randomness. Although the arrangement of diamond grits are tried to improve the uniformity of diamond wear, the effect is limited. It is due to the wear mechanism of diamond abrasive grit is not yet clear.Cubo octahedral diamond abrasive grits are employed to fabricate brazed single diamond grit tool contact with workpiece by point, line and plane. Nine different scratching types are designed through combining with the crystal structure of diamond and the scratch direction. Material removal volume, scratching force, wear volume and wear morphology are tracked during diamond grits scratch on typical brittle materials(sapphire) and plastic materials(Ta12W). The influence of contact type, workpiece material and scratching direction on the wear of diamond abrasive wear is analyzed. The theoretical model of diamond abrasive grit scratching on workpiece material is established by using the smoothed particle hydrodynamics(SPH) method and theoretical derivation. The influence of different orientations on the diamond scratching process and the characteristics of stress are analyzed. Finally, the wear theory model is established to explain the wear mechanism of diamond abrasive grit. Through the above analysis and discussion, the main research results can be summarized as follows:(1) The main impact factor of the mechanical wear of diamond abrasive grit is the contact type, workpiece type and scratching direction. The contact type has the most significant impact on the mechanical wear of diamond grit. The wear resistance of diamond grit with plane contact type is significantly higher than that of diamond grit with point and line contact type. The wear resistance of diamond grit with {100} plane contact type is best. The main reason of the poor wear resistance of diamond grit with point and line contact is because the small contact area leads to higher stress.(2) The mechanical wear morphology of diamond abrasive grit mainly includes: crack, step fracture, river cleavage and flaky cleavage. The flaky cleavage is produced on {111} plane, and step surface fracture along the {111} plane, and the cracks mainly propagate along the <110> crystal direction. The four types of mechanical wear morphology are observed in scratching on sapphire. However, the wear morphology mainly includes river cleavage and flaky cleavage during scratching on Ta12 W.(3) The type of workpiece material has a significant impact on diamond wear. The diamond grits are fracture along a certain angle due to the compressive stress in scratching on sapphire(brittle material). The diamond grit fracture and form flat surface due to the shear effect and compressive stress in scratching on Ta12W(plastic material).(4) The theory model of wear mechanism for diamond abrasive grit is established, the stress characteristics model with different contact types are analyzed. The wear characteristics of diamond grit could be better explained. The causes of wear morphology of diamond abrasive grit could be explained by the PBC model.The research results of this paper enrich the theoretical study of the mechanical wear mechanism of diamond abrasive grit, and have practical guiding significance for the optimization of diamond abrasive tool performance and fabrication of new diamond abrasive tools.