摘要
目的 探究石墨烯涂层对单晶铜基底摩擦特性的影响,揭示石墨烯涂层的微观减摩和基底强化机制。方法 基于AIREBO、EAM、Lennard-Jones混合势函数和Verlet算法,采用分子动力学法对铜基底/石墨烯涂层(Cu/Gr)和铜基底(Cu)的摩擦行为展开研究,结合基底位错、承载直径、划切圆角、划切刃角的变化规律,分析石墨烯涂层对法向力和摩擦力的影响。结果 在纳米压痕中,石墨烯涂层使基底压入边缘处产生了划切圆角,当压入深度为3.0 nm时,基底承载直径由4.6 nm增至8.2 nm,法向承载力由62.63 nN提高至514.32 nN;在摩擦过程中,石墨烯涂层抑制了基底表面的犁沟效应,使位错密度由0.06 nm^(-2)提升至0.15 nm^(-2);当压入深度相同时,石墨烯涂层使基底具有更小、更稳定的摩擦因数,最终使摩擦因数降低了61.43%~77.81%;当下压力为150 nN时,石墨烯涂层使划切刃角由90°降至32°,摩擦力由75.72 nN降至21.51 nN。当Cu/Gr基底上的划切刃角由32°降至17°时,摩擦力由21.51 nN降至9.08 nN。结论 石墨烯涂层的束缚机制增大了基底表面的承载直径,增大了基底内的位错密度,进而提高了法向承载能力。石墨烯涂层的束缚机制降低了划切刃角,降低了摩擦力,提升了基底的摩擦性能。
Graphene coating technology can provide an effective solution to the problems such as energy loss and part failure in mechanical system caused by friction and wear on material interface.Moreover,graphene coating can not only retain original excellent properties of substrate,but also produce new synergistic effects to improve properties of composites.The work aims to investigate the effect of graphene coating on friction characteristics of single crystal copper substrate and reveal the micro friction reduction and substrate strengthening mechanism of graphene coating.Based on AIREBO,EAM,Lennard Jones mixed potential function and Verlet algorithm,the friction behaviors of 25.0 nm×20.0 nm×9.0 nm copper substrate/graphene(Cu/Gr)and copper substrate(Cu)friction were studied by molecular dynamics method.Firstly,diamond indenter was used to simulate the nano indentation on the substrate at the pressing speed of 50 m/s to explore the strengthening mechanism of graphene coating on the substrate.Then,diamond indenter was used to scratch 3.0 nm on the substrate surface in the x direction at speed of 20 m/s under pressing depth of 1.5,2.0,2.5,3.0 nm,to explore the effect of different scratching depths on friction characteristics.Finally,diamond indenter with different scratching radii(2.0,3.0,4.0 nm)was used to scratch on the substrate under 150 nN normal force to reveal the restraint friction reduction mechanism of graphene coating.In the process of nano indentation and friction,the information such as normal force,friction force,dislocation density,bearing diameter,scratching edge angle and scratching fillet were collected and analyzed.In the nano indentation process,graphene coating restraint mechanism caused scratching fillet at pressing edge of substrate,which changed the substrate load-bearing effect.When the pressing depth was 3.0 nm,graphene coating increased bearing diameter of substrate from 4.6 nm to 8.2 nm,and increased normal force from 62.63 nN to 514.32 nN.Besides,graphene coating inhibited furrows effect during friction process,reduced z-direction displacement height of substrate from 0.94 nm to 0.43 nm,and increased the dislocation density from 0.06 nm^(-2)to 0.15 nm^(-2).When the pressing depth was the same,graphene coating increased friction force and normal force,but the normal force was increased more obviously and the friction coefficient of Gr/Cu substrate was more stable.Finally,graphene coating decreased the friction coefficient by 61.43%-77.81%.Moreover,graphene coating reduced scratching edge angle of substrate from 90° to 32°and decreased friction from 75.72 nN to 21.51 nN at 150.00 nN normal force.When scratching edge angle was reduced from 32° to 17° on Cu/Gr substrate,friction was decreased from 21.51 nN to 9.08 nN and smaller scratching edge angle was beneficial to decreasing friction.Graphene coating not only improved the surface quality of copper substrate after scratching,but also increased the structural defects of the crystal in the copper substrate.Graphene coating restraint mechanism causes scratching fillet at pressing edge of substrate,increases bearing diameter and dislocation density in the substrate,inhibits the furrow effect and improves normal load-bearing capacity,and also reduces the scratching edge angle and friction and improves the friction performance of the substrate.
作者
冉迪
郑鹏
苑泽伟
王宁
RAN Di;ZHENG Peng;YUAN Ze-wei;WANG Ning(School of Mechanical Engineering,Shenyang University of Technology,Shenyang 110870,China;School of Mechanical Engineering,Shenyang Urban Construction University,Shenyang 110870,China;Engineering Training Center,Shenyang University of Technology,Shenyang 110167,China)
出处
《表面技术》
EI
CAS
CSCD
北大核心
2023年第5期61-70,共10页
Surface Technology
基金
国家自然科学基金(52275455,52005345)
辽宁省教育厅科学研究经费项目(LJGD2020003,LJKZ0160)。
关键词
铜基底
石墨烯涂层
减摩机制
摩擦特性
分子动力学
位错密度
承载直径
划切刃角
copper substrate
graphene coating
friction reduction mechanism
friction characteristics
molecular dynamics
dislocation density
bearing diameter
scratching edge angle
