Failure analysis and optimum structure design of PDC cutter

Abstract

The PDC (Polycrystalline Diamond Compact) cutter is widely prevailed in the markets of measuring and cutting tools, down-hole tools of oil and gas drilling, min-ing and geothermal drilling industries. However, PDC cut-ters failure results in reduced bit life and low efficiency rock breaking thereby limiting the popularity and applica-tion of drilling technology. Drilling practice shows that the failures of PDC cutters mainly include mechanical wear, fracture and stripping of PCD (Polycrystalline Diamond). Finite element models of conventional PDC cutter and the multi-face PDC reinforced cutter were established, and the failure reasons were discussed by simulation. It was found that the residual stress and mechanical wear in the PDC cutters, which will cause the reduction of crystalline cohe-sion to result in local cracks inside PCD; the maximum equivalent stress of conventional PDC cutter appeared near the joint surface of the composite layer and gradually ex-tends outward. Therefore, the fracture and stripping of cut-ter is mainly beginning from the combination of surface area, PCD loses its back-up and the destruction then grad-ually extended to the surface. The size of the cutting force is proportional to the cutting angle of conventional PDC cutter, so it can set as objective function to design of the PDC cutter structure. Designed the multi-face PDC rein-forced cutter will change external variable load of the cut-ting edge into internal surface load of multi-face, and it changed the nature of the stress of the teeth, make the cut-ter has high resistance to shear failure capacity. By finite element simulation of conventional PDC cutter and multi-face PDC reinforced cutter stresses, the results show that the multi-face PDC reinforced cutter significantly reduces the internal stress distribution and the peak load, enhance the bonding force between PCD and WC, which can effec-tively reduce the fracture and stripping the probability of occurrence of the failure, and have great engineering sig-nificance to the comprehensive performance and service life of PDC bit.