To improve the tribological performance of YG8 cemented carbide.
Micropits were fabricated on the surface of YG8 cemented carbide and subsequently filled with microcapsules using UV-curable resin as a binder. The used microcapsules, featuring polysulfone (PPSU) as the shell material and a composite core composed of hexafluorophosphate ionic liquid ([BMIM]PF6) and calcium fluoride (CaF2), were synthesized via in-situ polymerization to form CaF2/[BMIM]PF6@PPSU solid–liquid dual-core microcapsules.
The prepared microcapsules were uniformly dispersed, with regular spherical morphology and smooth, dense surfaces. The capsule wall thickness was approximately 1.7 µm, and the average particle size was about 11.5 µm. Thermogravimetric analysis shows that the microcapsules have a liquid core content of approximately 40 Wt.% and a solid core content of approximately 1.5 Wt.%, and are thermally stable up to 323°C, indicating their potential as high-temperature lubricants. Tribological tests were conducted to investigate the effects of microcapsule content and applied load on the friction coefficient and wear rate of the GCr15 steel/YG8 cemented carbide tribo-pair. Results showed that even at a low microcapsule content of 5 Wt.%, both friction coefficient and wear rate were significantly reduced. At a 20 Wt.% content, the friction coefficient dropped to a minimum of 0.17, and the wear rate reached 0.171 × 10–6 mm³/(N·m), representing reductions of 70 and 71%, respectively, compared with untreated YG8 cemented carbide.
The originality of this study lies in the pioneering design and successful fabrication of solid-liquid dual-core microcapsules (CaF2/[BMIM]PF6@PPSU) with a polysulfone (PPSU) shell encapsulating a composite core of hexafluorophosphate ionic liquid ([BMIM]PF6) and calcium fluoride (CaF2). Innovatively, these microcapsules were embedded into laser-textured micropits on the surface of YG8 cemented carbide via a vacuum-assisted and UV-curing technique, constructing a novel self-lubricating composite coating. The significant value of this coating is demonstrated by the synergistic effect of the solid and liquid lubricants, which during friction substantially reduce the friction coefficient (by up to 74%) and wear rate (by up to 71%). Furthermore, the excellent thermal stability of the microcapsules (withstanding temperatures up to 323°C) provides a breakthrough solution for long-term self-lubrication of cemented carbide under harsh conditions such as high temperature and heavy load, showing broad application prospects in key mechanical components like high-performance cutting tools and molds.
