Tribological properties of lubricating oil with micro/nano-scale WS₂ particles

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.