Effect of humidity on the synergy of friction and wear properties in ternary epoxy-graphene-MoS2 composites

Abstract

Graphene and molybdenum-disulfide are considered to be one of the multifunctional materials that are extensively used in lubrication. However, the combined effects of these two materials on the tribological properties under different humidity are less explored. In this study, novel epoxy-graphene-MoS2 ternary composites are prepared by considering different particle concentrations of 5, 10, and 20 wt%. For analyzing the suitability of these composites in a humid environment, their tribological properties are tested under 40%, 60%, and 80% relative humidity and compared with pristine epoxy, binary epoxy-graphene, and binary epoxy-MoS2 composites. The reported friction coefficient and wear rate of ternary composites are significantly lower than those in each binary composite. A synergistic effect in ternary composites leads to much low friction coefficient and wear rate ranging between 0.0019 and 0.01 and 1.0 and 1.48 × 10−7 mm3/N-m, respectively. The formation of functional-graphene influences the wear mechanism in the ternary composite. In a similar environment, friction coefficient and wear rate of binary epoxy-graphene (0.017–0.028, 1.35–1.59 × 10−7 mm3/N-m) and binary epoxy-MoS2 (0.07–0.23, 1.4–1.67 × 10−7 mm3/N-m) composites are high. The ultralow friction values and light-weight of ternary composites make them suitable for practical application in the automotive industry for designing light-weight and rolling/sliding components such as bearings for ball joints.