WS2 nanoparticles anti-wear and friction reducing properties on rough surfaces in the presence of ZDDP additive

• The WS2 nanoparticles reduce friction and wear in presence of rough steel surfaces.
• The WS2 nanoparticles are trapped on the steel grooves.
• The nanoparticles trapped in the grooves are able to provide proper lubrication in case of nanoparticles starvation in the contact.
• The friction reducing and anti-wear properties of the nanoparticles are enhanced when ZDDP additive is present in the lubricant.
• ZDDP protects WS2 sheets from oxidation.

The effect of WS2 nanoparticles used as lubricant additives in PAO alone and in presence of ZDDP additive on the lubrication of rough surfaces has been studied at 100 °C in the boundary lubrication regime. The results showed that the use of nanoparticles in PAO base oil reduces both wear and friction by around 70% compared to PAO. The surface analyzes revealed that a tribofilm is formed on the steel surface and that nanoparticles can be trapped in the steel grooves. These trapped nanoparticles could provide proper lubrication of the contact zone in case of nanoparticle starvation. The presence of ZDDP additive in the lubricant enhances the friction reducing and anti-wear effect of the nanoparticles.