Strengthening and Toughening Mechanism and Impact Resistance of Graphene Nanosheet–Silicon Carbide Whisker Hybrid Reinforced PDC Composites

Abstract The toughening mechanism and impact resistance of Graphene Nanosheets (GNs) and Silicon Carbide Whisker (SiCw) hybrid reinforced polycrystalline diamond compact (PDC) were systematically investigated. Pure PDC and reinforced PDC composites with different ratios were prepared by High-Temperature and High-Pressure (HPHT) synthesis (5.5 GPa, 1450 °C), and their microstructures, mechanical properties, impact resistance, and thermal properties were comprehensively characterized. The results showed that the hybrid introduction of GNs and SiCw produced an effective synergistic reinforcing effect. Compared with pure PDC, the optimal hybrid ratio group (PDC+0.5 wt % GNs+1.0 wt % SiCw) exhibited the most favorable comprehensive performance among the tested groups: Apparent density increased to 3.63 g/cm3, Vickers hardness reached 56.4 ± 1.1 GPa, flexural strength and fracture toughness increased to 682 and 7.8 MPa·m1/2, while thermal conductivity stabilized at 550 W/(m·K) and Coefficient of Thermal Expansion (CTE) decreased to 2.5 × 10–6 /K. Microstructure analysis showed that the multiscale hybrid reinforcing phase effectively suppressed abnormal grain growth and significantly reduced porosity to 0.4%. Based on two-dimensional images and fractal geometry analysis, it was confirmed that the hybrid network greatly increased the curvature of crack propagation (τ = 1.38) and the fractal dimension (Df = 1.26), and the critical strain energy release rate (GIC) of the composite system was raised to 65.9 J/m2. A multidimensional performance radar system was used to reveal the cross-scale multidimensional synergistic strengthening and toughening mechanism of GNs and SiCw in PDC composites. This study not only provides a solid theoretical basis for the toughening design of high-end superhard materials under complex conditions in deep strata, but also opens up new avenues for the development of multidimensional nanocomposites in extreme service environments.