Tribological behaviours of ultrafine Sn/heat treated serpentine powder in grease

In order to improve the tribological performance of traditionally based lithium grease, ultrafine serpentine powder of 0·33 μm and Sn powder of 120 nm were prepared by ball mill and direct current arc plasma evaporation respectively. The milled serpentine powder was heat treated at 200, 500, 600 and 800°C in a muffle furnace separately with a four-ball wear test. Then, the tribological behaviours of lithium grease modified with complex powder with different ratios of ultrafine Sn/heat treated serpentine were investigated, and the effects of total concentration and load were discussed too. The optimal performance was achieved by the compound grease with 1 wt-% complex powder and 1∶1 Sn/serpentine powder (heated at 200°C). The friction coefficient and wear scar diameter decreased 25·5 and 42·5% respectively under 392 N compared with pure grease. The compound grease is much more suitable under high load rather than low load.