Surface passivation by graphene in the lubrication of iron: A comparison with bronze

Abstract

It has been recently reported that graphene is able to significantly reduce the friction coefficient of steel-on-steel sliding contacts. The microscopic origin of this behavior has been attributed to the mechanical action of load carrying capacity. However, a recent work highlighted the importance of the chemical action of graphene. According to this work graphene reduces the adhesion of iron interfaces by reducing the surface energy thanks to a passivation effect. The aim of the present work is to clarify the still debated lubricating behavior of graphene flakes. We perform pin-on-disc experiments using liquid dispersed graphene solution as a lubricant. Two different materials, pure iron and bronze are tested against 100Cr6 steel. Raman spectroscopy is used to analyze the surfaces after the friction tests. The results of these tests prove that graphene flakes have a beneficial effect on the friction coefficient. At the same time they show a tendency of graphene to passivate the native iron surfaces that are exposed during sliding as a consequence of wear

Interfacial Charge Density and Its Connection to Adhesion and Frictional Forces

“…Moreover, a simple functional relation between the strength of adhesion E adh and the corrugation of the PES ∆V is discovered. We also explain that one key function of lubricant materials is surface passivation to impede the charge flow at the interface [20][21][22][23]. Finally we show that the PES corrugation and in turn adhesive friction are determined by the variation of the total charge density at the interface during sliding.…”

“…Experiments have shown that lubricant additives containing sulfur or graphene can reduce the friction and wear of iron and steel significantly [23,26,27]. Likewise, friction at diamond interfaces is greatly diminished in the presence of H 2 [28].…”

<em>Ab Initio</em> Molecular Dynamics Simulation of Tribochemical Reactions Involving Phosphorus Additives at Sliding Iron Interfaces

“…[16] Iron phosphide presents low friction, as evidenced by the experiment and in first principles calculations. [21] While a similar lubricating effect can be provided by sulfur, [40] and graphene [41][42][43] it is not provided by atomic oxygen. [21] The AIMD simulations reveal that O adsorption does not compete with P adsorption during TMPi decomposition.…”

The Flexible Lubrication Performance of Graphene Used in Diamond Interface as a Solid Lubricant: First-Principles Calculations

“…Especially in the field of tribology, graphene has been considered as one of the most promise nanoscale lubricating material [24,25]. Different researchers have shown that graphene can be used as an excellent coating to reduce the surface and interface friction and wear of iron, bronze, steel, Ni, Re and Pt [26][27][28][29][30][31][32]. Recently, the interfacial properties of diamond film and graphene have also aroused much interesting in experimental and theoretical calculation researches [1,33,34].…”