▎ 摘　　要

Graphene nanosheets were used as additives in the preparation of polycrystalline diamond compact (PDC) composites to overcome the low fracture toughness and heat resistance of PDC composites. The PDC composites were then sintered at a pressure of 5.8 GPa and a temperature of 1500 degrees C. Subsequently, the mechanical properties, microstructure, and toughness mechanism of PDC composites modified by graphene nanosheets were studied. The PDC sample prepared by adding 0.2 wt% graphene nanosheets had the best comprehensive performance. Compared with the sample without graphene nanosheets, the impact toughness of the sample with 0.2 wt% graphene nanosheets improved by 29.78%, while the heat-resistant temperature increased by 34.5 degrees C. The hardness and wear resistance of the sample did not show any significant decrease and were essentially the same as those of the unmodified PDC composite sample. Two factors were found to influence the toughening mechanism. On the one hand, the lubricating effect of graphene promoted particle rearrangement, pore filling, and mutual sliding between adjacent diamond particles, which resulted in a denser and more uniform PDC composite material. On the other hand, the graphene nanosheets at the triangular grain boundaries were interspersed in the cobalt binder and led to the formation of a unique structure of "cobalt-graphene nanosheets". This unique structure acted as the skeletal structure and effectively prevented fracture crack propagation.