Atomistic insights into friction and wear responses of NiCoCr medium entropy alloy: Influence of pre-strained monolayer graphene coating

P Chen and XQ Ye and JW Yang and LY Wu and XX Qiao and J Zhang and LH Su, JOURNAL OF ALLOYS AND COMPOUNDS, 1014, 178697 (2025).

DOI: 10.1016/j.jallcom.2025.178697

This study investigates the friction and wear responses of the NiCoCr medium entropy alloy (MEA), which was coated with graphene but with different pre-strain conditions, through molecular dynamics simulations. Compressive and tensile pre-strains were introduced into the graphene by uniformly scaling the graphene bond lengths, then applying the strained graphene layer over the NiCoCr MEA surface. Using the bare NiCoCr MEA as a benchmark, we examined the factors such as coefficient of friction, wear amount, von Mises stress, indentation depth, dislocation activities, and bond distribution to analyze the effects of pre-strained graphene coating. The results reveal that a monolayer of graphene coating without pre-strain effectively reduces the average coefficient of friction (from 0.60 to 0.13) and the average number of worn atoms (from 11,353 to 1910). This reduction is primarily due to the stress- shielding effect, which mitigates the excessive stress transfer to the underlying NiCoCr MEA. Additionally, a tensile pre-strain minimizes the graphene puckering and enhances the load-bearing capacity, further improving the friction and wear performance. In contrast, a compressive pre-strain induces the wrinkling and puckering, which creates spaces for alloy pileup and compromises the smooth interface essential to reduce both friction and wear.

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