【作者】 石琛；

【导师】 毛大恒；

【作者基本信息】 中南大学 ， 机械工程， 2010， 博士

【摘要】 随着石油资源的日益紧缺和石油价格的持续高涨以及世界各地日趋严格的排放与节能法规的出台,节能减排已经成为汽车工业关注的热点。本研究结合纳米摩擦学开发纳米WS：环保节能发动机润滑油,适应目前社会发展的需要,对全国资源节约型和环境友好型社会建设具有重要意义。本文首先在通过钨硫直接反应法制备出微米WS2颗粒的基础上,采用强超声／螺旋搅拌球磨多能场复合细化法成功制备出平均激光衍射粒度为95nm的片状纳米WS2颗粒,通过与微米WS2颗粒的性能对比分析发现,纳米WS2颗粒具有更加优良的金属表面吸附特性、分散稳定性、润滑性能和较佳的热稳定性(空气气氛下)。而机理分析初步表明,强超声／螺旋搅拌球磨复合细化法主要通过冲击粉碎作用,辅以摩擦剪切粉碎作用和强超声产生的大量·OH对颗粒细化的促进作用来达到超细化WS2粉末的目的。针对润滑油中纳米WS：颗粒易自发团聚的特点,在强超声／球磨搅拌复合作用下采用修饰剂SA对纳米WS2颗粒进行表面修饰处理,发现该方法修饰后的纳米WS2颗粒在PA06、菜籽油和PriEco3004三种环保型基础油中的分散稳定性均最佳,并且当润滑油中纳米WS2颗粒的质量添加量为2%时,SA的最佳用量为0.5%。机理分析表明,强超声／球磨搅拌的复合作用起到对纳米WS：团聚体的解团聚作用,并使解聚后的纳米WS2颗粒表面活性增强,造成颗粒表面的羟基(-OH)与油液中表面修饰剂SA的羧基(-COOH)发生类似于醇与酸的酯化反应,从而使得纳米颗粒表面特性由亲水疏油转变为亲油疏水,经表面修饰后的纳米WS2颗粒表面的长碳链形成的空间位阻层和润滑油分子形成的溶剂化层共同防止了纳米颗粒的碰撞团聚,最终使得解聚后的纳米WS2颗粒长期稳定分散于润滑油介质中。通过系列四球摩擦对比实验发现,在基础油PA06、菜籽油中添加2%的纳米WS2颗粒对基础油在常温、高温、低载、高载、低速、高速等工况下润滑性能的改善最显著,且纳米WS2颗粒的改善效果优于纳米MoS2和纳米石墨。此外,纳米WS2颗粒与T462A、T202、T323和T451A等几种常用于发动机润滑油的极压抗磨添加剂在PA06和菜籽油中的配伍性良好,尤其分别与T462A、T202复配时具有增效作用。在自制发动机模拟实验台架和真实汽车上进行了纳米WS2颗粒的发动机应用实验,结果经发动机模拟台架实验发现,纳米WS2能减少发动机活塞环磨损量27.6%,能降低发动机油耗13%-28%,能使发动机排放尾气中HC、CO、NOx等有害气体的含量分别降低18.6%-37.6%、7.7%14.3%、8.8%-19.7%；而通过行车实验发现,纳米WS2能提高传统发动机润滑油的使用寿命1.5倍,并能有效降低发动机的燃油消耗,最大节油率可达到38.50%,最小节油率也有16.39%,平均节油率为20.26%,表现出优良的节能减排特性。本文在四球摩擦实验机、AW-3型抗磨试验机和发动机模拟实验台架上进一步考察了纳米WS2颗粒的自修复特性,结果表明,PA06和菜籽油中纳米WS2颗粒在常温、100℃和200℃下均能对摩擦副表面的微损伤、微裂纹实现在线原位动态自修复,但在低载下修复效果不明显；此外,纳米WS2颗粒能减少磨粒磨损表面和粘着磨损表面的表面粗糙度,使表面平整,避免磨损加剧,能改善活塞环磨损表面的形貌,使其平整,能减小发动机内部的磨损烈度指数,使发动机内部的磨损严重程度降低,这表明纳米WS2颗粒还能对已存在的磨损表面实现良好的自修复作用。为研究环保型润滑油中纳米WS2颗粒的作用机理,对摩擦表面进行了XPS分析、EDS分析和氩离子溅射深度剖析,结果表明,环保型润滑油中纳米WS2颗粒的润滑过程可分为流体润滑阶段和混合润滑阶段,前一阶段主要通过纳米WS2颗粒增加流体润滑油膜厚度来改善润滑,且摩擦过程中,纳米WS2颗粒会逐渐沉积于摩擦表面；后一阶段初期摩擦主要发生在纳米WS2沉积膜内部,在摩擦剪切力的作用下沉积膜中的纳米WS2颗粒发生择优取向分布,从而使得沉积膜的减摩性能得到提高,后期由于摩擦表面温度的升高,沉积的纳米WS2颗粒重新被活化,并随摩擦在表面由富集区(如磨粒磨损表面的犁沟区和粘着磨损表面的凹坑区)向四周转移,在摩擦表面微区高温高压的作用下与金属微凸体作用生成具有低摩擦系数的纳米FeS和纳米FeS04,纳米FeS和纳米FeSO4继而受摩擦剪切作用在摩擦表面滑移铺展,最终将磨损表面修复平整,并在表层形成由纳米W03、纳米FeS、纳米FeS04及纳米WS2组成的致密极压抗磨修复层,该修复层不仅阻止了摩擦表面之间的直接接触,而且拥有很高的承载能力,使得由剪切应力引起的弹性变形和塑性变形局限于修复层,因而有效地抑制了摩擦表面的粘着磨损和接触疲劳,起到保护摩擦表面的作用。此外,发动机缸压分析实验表明,在发动机中纳米WS2颗粒于汽缸-活塞环处密封面形成的自修复层,改善了密封性,提高了缸压,进而保证了更加有效的燃料燃烧,使得燃油消耗和HC、CO、NOx等有害气体的排放降低。最后,本文选用精炼菜籽油、多元醇酯PriEco3004、聚α烯烃PA06和高压加氢150BS光亮油按比例调配后加入粘度指数改进剂T618、降凝剂LZL803B和抗氧剂L01、L115后获得综合性能优良的环保型基础油,然后加入纳米WS2颗粒和表面修饰剂SA,经分散处理后配以其它功能添加剂制备出达到15W/40级别油品粘度要求且使用性能与SL级发动机润滑油相当的纳米WS：发动机润滑油,其可生物降解性良好,并且与国内外知名节能型发动机油的对比发现,纳米WS：环保节能发动机润滑油无论是润滑性能还是节能减排性能均更加优良。更多还原

【Abstract】 Along with the increasing shortage of petroleum resources, the sustaining upsurge of petroleum prices, and the policy making of gradually strict energy-saving and emission regulations around the world, energy-saving and emission reduction have become the research hotspot of auto industry. Combining with nano-tribology, this research developed nanometer WS2 green energy-saving engine lubricating oil, which is accommodated the needs of social development, and will play an important role in national resource-saving and environment-friendly society construction.In this thesis, based on the preparation of micrometer WS2 particulates by the method of W-S direct reaction,sheet nanometer WS2 particulates were prepared by the compound thining method of high power ultrasonic/spiral mixing ball-milling, whose average particle size is 95nm. The property contrast analysises between nanometer and micrometer particulates show that, nanometer WS2 particulates have better metal surface adsorption property, dispersion stability, lubricating performances and goodish thermostability. The mechanism analysises preliminarily indicate that, it’s mainly through impact comminution and accessorially through friction shearing comminution and the promoter action of-OH free radicals produced by high power ultrasonic for compound thining method of high power ultrasonic/spiral mixing ball-milling to achieve the goal of ultrafine grind micrometer WS2.For the spontaneous glomeration characteristic of nanometer WS2 particulates in lubricating oil, this thesis used surface modifier SA to modify the nanometer WS2 particulates surfaces under compound action of high power ultrasonic/ball-milling stir, and the results show that the modified nanometer WS2 particulates by such method possess excellent dispersion stability in green base oil (PAO6, rapeseed oil, or PriEco3004), and when the additive amount of nanometer WS2 particulates is 2wt%, the best additive amount of SA is 0.5wt%. Mechanism analysises indicate that, compound action of high power ultrasonic/ball-milling stir can break up the nanometer WS2 agglomerations and then strengthen the surfactivity of nanometer WS2 particulates, bringing about the esterification reaction between hydroxide radicals on particulates’ surfaces and carboxyl group of the modifier SA, and leading to the change of particulates’ surface characteristics from hydrophilicity to lipophilicity. After surface modifying, the long carbon chains on surface can form stereo-hindrance layer, combined with solvation layer formed by lubricant molecule, to prevent nanometer particulates from aggregate, and ultimately make nanometer WS2 particulates dispered in lubricating oil stably for long time.Series of four-ball tribology tests show that,adding 2wt% nanometer WS2 particulates into green base oil PAO6 or rapeseed oil can improve the lubricating performances of base oil under each working condition such as normal temperature, high temperature, low load, high load, low speed, high speed observably, and the improving effect of nanometer WS2 particulates is better than that of nanometer MoS2 particulates or nanometer graphite particulates. And moreover, in PAO6 or rapeseed oil nanometer WS2 particulates have good compatibility with other antiwear additives such as T462A,T202, T323 and T451A, especially when confected with T462A or T202, nanometer WS2 particulates have synergistic effect.Application experiments of nanometer WS2 particulates in engine have been done on the self-designed engine simulant bench and true automobile. The results of engine simulant bench tests show that, nanometer WS2 particulates can reduce the abrasion of piston ring in engine by 27.6%, and reduce fuel consumption by 13%～28%, and decrease the contents of harmful gases such as HC, CO, NOx in tail gas respectively by 18.6%-37.6%,7.7%-14.3%,8.8%-19.7%. The results of road test indicate that, nanometer WS2 particulates can improve the service life of traditional engine lubricating oil by 1.5 times, can reduce the fuel consumption observably(by 38.50% to the greatest extent and by 16.39%to the smallest extent, and the average rate of saving fuel is 20.26%). All of tests illustrate that nanometer WS2 particulates have excellent energy conservation & emission reduction properties.This thesis investigated the auto-reparing properties of nanometer WS2 particulates ulteriorly on four-ball machine, AW-3 anti-wear machine and engine simulant bench. Results indicate that, nanometer WS2 particulates can realize the on line in-situ dynamic repair to the tiny damages on surfaces in PAO6 or rapeseed oil under normal temperature, 100℃and 200℃, but the repairing effect will become unconspicuous under low load. In addition, nanometer WS2 particulates also can reduce the surfaceness of grain wear surface or adhesive wear surface, smoothing the wear surface and avoiding abrasion from worsen, and nanometer WS2 particulates can better the appearance of piston ring’s wear surface, and reduce the index of wear severity in engine, lowering engine’s interior abrasion, all of which tell us that nanometer WS2 particulates also can realize good repair effect to the existed wear surface.To research the nanometer WS2 particulates’mechanisms of action in green lubricating oil, series of XPS analysises, EDS analysises and argon ion sputtering depth analysises were done. All the results indicate that, in green lubricating oil, the lubricating process of nanometer WS2 can be divided into fluid lubrication stage and mixed lubrication stage. In the former stage, nanometer WS2 particulates mainly increase the thickness of oil film and thus improve the lubrication, and moreover nanometer WS2 particulates can deposit on the friction surface during friction. In the beginning period of the latter stage, friction mainly happens in the nanometer WS2 deposition film, the nanometer WS2 particulates in deposition film occur preferred orientation distribution under the effect of friction shear force, which improves the anti-friction property of the deposition film. In the later period of the latter stage,because of the increasement of friction surface temperature,the deposited nanometer WS2 particulates are activated and transfer from abundant regions (e.g., furrow regions on grain wear surface or concave regions on adhesive wear surface) to perimeter zone, and react with metal convex body affected by tiny area high temperature and high pressure during friction, and generate nanometer FeS and nanometer FeSO4, which are affected by friction shear force and glide on the friction surface, ultimately the wear surfaces are repaired to smooth surfaces, and a compact anti-pressure/anti-wear repair layer which consists of nanometer WO3, nanometer FeS, nanometer FeSO4 and nanometer WS2 is formed, this repair layer not only prevent metal surfaces from direct touch, but also has high carrying capacity, which can limit the elastic deformation and plastic deformation caused by shear stress into the repair layer, and therefore restrain adhesive wear and contact fatigue effectively. In addition, the engine cylinder pressure analysis illustrates that, the repair layer formed by nanometer WS2 particulates on sealing face improves the tightness and increases the cylinder pressure, and then ensures more effective fuel burning, which reduces fuel consumption and emission of the harmful gases such as HC, CO and NOx.Finally, this thesis chose and mixed refined rapeseed oil, PriEco3004, PAO6 and 150BS bright stock proportionally,and added viscosity index improver T618, pour point depressant LZL803B, antioxygen L01, L115, then the green base oil with excellent combination properties was prepared.After that, nanometer WS2 particulates and modifier SA were added into green base oil and treated under the compound action of high power ultrasonic/ball-milling stir, then mixed with other functional additives, nanometer WS2 engine lubricating oil was prepared, whose viscosity meets the requirement of 15W/40 level engine lubricating oil,service properties are equivalent to SL level engine lubricating oil, and biodegradability is good. The performances contrasts with the famous domestic and overseas energy-saving engine lubricating oil show that, nanometer WS2 environmental and energy-saving engine lubricating oil has better lubricating performances and energy conservation & emission reduction properties.更多还原