Exploring the lubricating effect of graphene in nano AlCoCrFeNi high-entropy alloy

The graphene/AlCoCrFeNi high-entropy alloy (HEA) composite demonstrated numerous exceptional properties, including enhanced mechanical performance, superior friction and wear resistance, and excellent thermal stability. However, the lubrication mechanism of graphene remains unclear. In this study, we thoroughly analyzed the material's frictional force, coefficient of friction (COF), surface damage, energy variations, temperature distribution, stress field characteristics, and internal defect evolution during the wear process through molecular dynamics (MD) simulations. The results indicate that the graphene coating significantly reduces frictional force and fluctuations in the friction curve, while the graphene interlayer eliminates the traditional stable fluctuation stage, reduces nano-scratch defects, and slightly lowers the radial distribution function (RDF) peak. Concurrently, the maximum dislocation depth decreases with increasing scratch distance. Temperature and grain size exhibit minimal influence on Coating-HEA but substantially affect Composite-HEA, particularly as interfacial bonding strength peaks at 300 K. Notably, stacking faults (SFs) and other defects within Composite-HEA tend to reconstruct or annihilate under high-temperature conditions (1000 K). Furthermore, compared to the (110) and (111) crystallographic planes, the (001) plane mitigates interfacial stress concentration and further reduces the COF owing to its homogeneous atomic arrangement. This work provides mechanistic insights into the wear-resistant mechanisms of graphene-reinforced HEAs.