Tribological and thermal performance of graphene-enhanced lithium-based greases: impact of concentration on friction, wear, and stability

In this study, lithium-based greases enhanced with varying concentrations of graphene (0.5 wt.%, 1 wt.%, and 2 wt.%) were evaluated for their tribological and thermal performance. The Four Ball Wear Test, thermal imaging and thermogravimetric analysis (TGA) were used to assess the impact of graphene on friction reduction, wear resistance and thermal stability. The 0.5 wt.% graphene-enhanced grease demonstrated the most favourable results, with superior friction reduction, wear resistance and consistent lubrication over time. This is attributed to the uniform dispersion of graphene, which promoted the formation of a stable tribo-film and enhanced thermal conductivity. At higher concentrations (1 wt.% and 2 wt.%), graphene agglomeration led to diminished tribological performance, with increased friction and faster thermal degradation. TGA results further confirmed the superior thermal stability of the 0.5 wt.% sample, with delayed onset of decomposition compared to the other formulations. These findings suggest that a graphene concentration of 0.5 wt.% is optimal for improving the overall performance of lithium-based greases, providing a balance between friction reduction, thermal stability and wear resistance.