Grease-lubricated tribological contacts – Influence of graphite, graphene oxide and reduced graphene oxide as lubricating additives in lithium complex (LiX)- and polypropylene (PP)-thickened greases

Two types of thickener systems, lithium complex (LiX) and polypropylene (PP), were chosen to evaluate graphite, graphene oxide (GO) reduced (rGO) as grease additives at a concentration 0.1 wt%. To enhance the additive dispersibility, mixture polyalphaolefin oil (PAO) soluble synthetic polyalkylene glycol (OSP-68) was used base oil. The greases evaluated in i) silver-coated copper contacts simulating high-load electrical contact applications subjected fretting ii) steel/steel 4-ball wear test equipment. showed no positive effect on friction wear, neither nor tests. However, there is statistically significant difference scar diameter steel between two types, LiX PP. Thus, PP-grease lubricated more tribofilms iron constituents, indicating metal-to-metal contact. Hence, type has larger impact lubricating performance than do GO rGO additions. results demonstrate that addition graphene-based materials improve not straightforward. Rather, grease/graphene-based system many parameters influence results. work needed obtain better understanding possibly effects from additives.