The tribological properties of lubricating oil containing micro/nano-scale WS₂ (90 nm, 2 µm) and ionic liquid [C₇H₁₁F₃N₂O₃S] are evaluated using a four-ball friction tester. Results show that the addition of micro/nano-scale WS₂ can improve the tribological properties of the base oil; moreover, adding the ionic liquid as a solvent may lead to a better mixing of the micro/nano-scale WS₂ and base oil and promote the dispersion of WS₂ in the sample oil. The base oil with 90 nm nano-WS₂ and ionic liquid presents the best anti-friction and anti-wear properties at 1 wt.% content. The surface analysis of wear scars reveals that ploughing is the main cause of wear in the three bottom balls. Furthermore, the wear furrows of nano-WS₂ as lubricating additive are uniform and symmetrical and can homogenously appear on the friction area. This work proves that the micro/nano-scale WS₂ plays an important role in improving the performance of tribological properties of lubricating oil.

In the present work, the relationship curve of the coefficient of friction (COF) with varying loads of different morphology WS₂ lubricating additives in the friction process at various sliding speeds was studied. On this basis, wear marks and elements on the wear surfaces after friction were analyzed, and then the anti-wear and mechanism effects of WS₂ of different forms in the lubrication process were discussed. Meanwhile, the Stribeck curve was used to study the lubrication state of the lubricating oil in the friction process. It was revealed that the COF of lubricating oil containing lamellar WS₂ decreased by 29.35% at optimum condition and the minimum COF was concentrated at around 100 N. The COF of lubricating oil containing spherical WS₂ decreased by 30.24% and the minimum coefficient was concentrated at 120 N. The extreme pressure property of spherical WS₂ was better than that of lamellar WS₂, and the wear resistance of spherical WS₂ was more stable when the load was over 80 N. The different morphology of WS₂ additives can play anti-wear and anti-friction roles within a wide range of sliding speeds.

The microscale/nanoscale lamellar-structure WS₂ particles with sizes of 2 µm and 500 nm were synthesized by solid-phase reaction method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The synergies between microscale/nanoscale WS₂ particles and ZDDP as lubricating oil additives was evaluated by means of UMT-2 tribometer at room temperature. The wear scars were examined with SEM and electron-probe micro-analyzer (EPMA). The results show that the anti-wear properties were improved and the friction coefficient was greatly decreased with the simultaneous addition of WS₂ particles and ZDDP, and the largest reduction of friction coefficient was 47.2% compared with that in base oil. Moreover, the presence of ZDDP additive in the lubricant further enhances the friction-reduction and anti-wear effect of microscale/nanoscale WS₂. This confirms that there is a synergistic effect between WS₂ particles and ZDDP.

Moisture significantly reduces the load-carrying capacity of lubricating oil films, accelerates oxidative degradation, and induces equipment corrosion, making it a critical hazard factor affecting lubrication reliability. To overcome the limitations of existing methods for determining water content—such as complex operation, poor real-time performance, and high cost—this paper proposes a radio frequency identification (RFID)-based method for lubricating oil water content detection via the orthogonal fusion of phase and received signal strength indicator (RSSI) as an off-line analytical tool. The method exploits the signal variation characteristics when RF signals penetrate media with different dielectric properties; by analyzing the phase and RSSI of backscattered RFID signals, non-contact moisture sensing is achieved. First, a theoretical model integrating phase and RSSI for water content detection is established to reveal the differential response mechanisms of the two parameters to water content. Second, a detection method based on phase-RSSI orthogonal fusion is proposed, and performance evaluation metrics are constructed. Finally, comparative experiments with different detection approaches are conducted. It is found that as water content increases, the mean phase continuously rises with significantly increased fluctuation, while RSSI exhibits a linear decreasing trend, demonstrating clear complementary response characteristics. Compared with single-phase or single-RSSI methods, the proposed fusion method achieves a coefficient of determination (R²) of 0.95 over the 0–2.0% water content range, with reliable detection verified at concentrations as low as 0.1%, and exhibits superior detection sensitivity in the low-water-content range. Furthermore, it possesses a type-discrimination capability absent in single-parameter methods—that is, it can effectively distinguish whether response variations originate from moisture contamination or non-moisture interference. The method offers stable response and high detection efficiency, providing a new approach for accurate determination of water content in lubricating oil.