Roles of SiC Nanoparticle Sizes on High-Temperature Tribological Behaviors of Polycrystalline Diamond Compacts under Water-Based Drilling Fluids

This study investigates the effect of SiC nanoparticle size (100–500 nm) in water-based drilling fluids on polycrystalline diamond compact (PDC) thrust bearings’ tribological performance at 125 °C. Tribological tests reveal that the coefficient of friction (COF) increases gradually from 0.043 to 0.083 as particle size grows from 100 to 500 nm, compared to 0.132 in nanoparticle-free fluid, demonstrating nanoparticles’ friction-reduction capability. Wear rates similarly rise from 6.6 × 10–11 to 2.11 × 10−10 mm3/N·mm with increasing particle size, versus 4.97 × 10−10 mm3/N·mm without nanoparticles. Optimal performance occurs with 100-nm particles due to synergistic mechanisms: nanoparticle embedding in surface defects, formation of protective tribochemical films, and nanoscale polishing effects. Larger particles induce detrimental stress concentrations at interfaces, accelerating fatigue crack propagation through intensified impact forces. Concurrently, higher COF promotes thermomechanical coupling, elevating interfacial temperatures, and oxidative wear. The results highlight that smaller nanoparticles enhance lubrication through interfacial modification, while larger particles exacerbate wear through mechanical overload and thermal activation, providing critical insights for nanoparticle selection in high-temperature drilling applications.