Abstract: This paper aimed to study the anti-friction and anti-wear mechanism and to further reveal the formation mechanism of lubrication film generated by nanofluid on the grinding interfaces through molecular dynamics simulations. 1-butyl-3-methylimidazolium tetrafluoroborate (［BMIM］BF4 ionic liquid) was used as the base fluid of nanofluid. And spherical nanoparticles made of alumina and copper were taken as representatives of high-and low-hardness nanoparticles respectively. The results show that boundary lubrication layer is formed on the grinding interfaces in NMQL grinding of nickel-based alloy. Copper nanoparticle occurs a series of tribological behaviors on the grinding interfaces, such as compression, shear, spread and separation, because of the far lower hardness than that of abrasive grains and nickel-based alloy workpiece. A layer of solid lubricating film was finally formed by copper nanoparticle, which may reduce the contact areas between abrasive grain and workpiece, resulting in lowered tangential grinding force by 4.6 percent compared with MQL grinding. Alumina nanoparticle maintains the initial spherical nanostructure during grinding due to their higher hardness than that of nickel-based alloy workpiece. Three tribological behaviors, i.e. sliding, rolling and polishing, occur on the grinding interfaces. The polishing scratches may enlarge the wet areas of ionic liquid, and hence may reduce the contact areas between abrasive grain and workpiece. The rolling behavior of alumina nanoparticle that moves like rolling balls may transform the sliding friction between abrasive grain and workpiece into rolling friction. Tangential grinding force is therefore reduced by 6.6 percent compared with MQL grinding.

Key words: grinding, minimum quantity lubrication(MQL), nanofluid, spherical nanoparticle, tribological mechanism

摘要： 以1-丁基-3-甲基咪唑四氟硼酸盐（［BMIM］BF4离子液）作为纳米流体基液，以氧化铝和铜纳米颗粒分别作为高硬度类和低硬度类球形纳米颗粒的代表，用分子动力学模拟方法研究了球形纳米颗粒在镍基合金纳米流体微量润滑磨削界面减摩抗磨的摩擦学机理，并进一步揭示了纳米流体在砂轮磨粒/工件磨削界面润滑成膜的摩擦学机制。研究结果表明，在镍基合金纳米流体微量润滑磨削加工中，砂轮磨粒/工件磨削界面形成了边界润滑膜。由于铜纳米颗粒硬度远低于砂轮磨粒及镍基合金工件，会在磨粒/工件界面出现压缩、剪切、铺展和分离等一系列摩擦学行为，并形成一层固体润滑膜，这层固体膜通过减小磨粒工件之间的直接接触面积来减小切向磨削力，相较于微量润滑工况可使切向磨削力减小4.6%。由于氧化铝纳米颗粒硬度高于镍基合金工件，故在磨削过程中仍能保持原本的球形纳米结构，会在磨粒/工件界面出现滑移、滚动和抛光三种摩擦学行为，抛光划痕可增大离子液体的浸润面积，并减小磨粒工件之间的直接接触面积，“类滚珠”的滚动行为可将磨粒工件之间的滑动摩擦转变为滚动摩擦，从而使切向磨削力较微量润滑工况减小6.6%。

关键词: 磨削, 微量润滑, 纳米流体, 球形纳米颗粒, 摩擦学机制