The Role of Gradient Structure in the Integrated Performance of PDC Cutters

Addressing the urgent demand for high-performance polycrystalline diamond compact (PDC) cutters in deep/ultra-deep oil and gas exploration, this study optimized the PDC synthesis formulation through orthogonal experimental design. Under high pressure conditions (8.5 GPa and 1750 °C), we successfully fabricated both conventional homogeneous mixed PDC cutter (H-PDC) and gradient-structured PDC cutter (G-PDC) featuring a "fine-grained work layer/coarse-grained transition layer" structure. Microstructural characterization reveals that the gradient structure facilitates uniform distribution of cobalt binder, suppresses cobalt aggregation, enhances interlayer interfacial bonding, and generates higher residual compressive stress. The cobalt content in the G-PDC work layer is 9.16 wt.%. After acid leaching for cobalt removal, the cobalt content decreased to 2.49 wt.%. Performance evaluations demonstrate that G-PDC achieves a wear resistance lifespan of 920 passes, superior to H-PDC (800 passes). The average impact toughness of G-PDC reaches 740 J, representing approximately 107% improvement over H-PDC. Furthermore, the gradient structure alleviates thermal expansion mismatch, increasing the thermal stability temperature by about 30 °C. This research confirms that combining high pressure synthesis technology with gradient structural design can synergistically enhance the wear resistance, impact toughness, and thermal stability of PDC cutters, providing a viable pathway for developing next-generation superhard composites for extreme working conditions.