Investigation on the tribological performance of [BMIM]PF6/5CB@PUF dual-core microcapsule-filled microtextured cemented carbide

Abstract To address the poor friction and wear resistance of YG8 cemented carbide under starved lubrication, this study develops a dual-core microcapsule lubrication strategy based on the synergistic action of an ionic liquid and a liquid crystal. Dual-core microcapsules encapsulating 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6) and 5CB liquid crystal within a poly(urea-formaldehyde) (PUF) shell were synthesized via in situ polymerization and subsequently filled into laser-fabricated microtextures on YG8 surfaces using a photocuring process. Thermogravimetric analysis confirmed successful encapsulation of 55.8 wt% [BMIM]PF6 and 16.2 wt% 5CB, while scanning electron microscope (SEM) characterization showed uniform spherical morphology and good structural stability. Tribological tests under starved lubrication revealed that microtextures filled with 15 wt% dual-core microcapsules at a 7% texture area density achieved the best performance, yielding an ultralow coefficient of friction (0.089) and a wear rate of 0.133 × 10−6 mm3/(N·m). Compared with untextured YG8, these values represent reductions of 86.7% and 96.3%, respectively. Mechanistic analyses (SEM, energy-dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy) demonstrated that friction-induced rupture of the microcapsules releases [BMIM]PF6 and 5CB, forming a stable boundary lubricating film while the microtextures act as reservoirs to capture wear debris. This work introduces a robust and efficient lubrication strategy for cemented carbide components and provides new insights into the synergistic tribological behavior of ionic liquids and liquid crystals in microtextured systems.