Reduction of Friction by Functionalised Viscosity Index Improvers

A range of functionalised polymethacrylate copolymers have been synthesised with different functionalities, polymer architecture and molecular weight. It is shown that appropriately functionalised block copolymers give enhanced film thickness and greatly reduced friction under low entrainment speed conditions, even with polymer concentration as low as 1% wt. This behaviour almost certainly results from the formation of an adsorbed brush-like film of thickness ca 20 nm on each polar surface. These films provide a highly viscous inlet that promotes fluid entrainment and thus maintains a separating film down to very low entrainment speed. The adsorbed polymer films are also able to maintain separation in stationary contact conditions. Randomly distributed copolymers do not show this type of behaviour. The friction reduction observed is more effective in unidirectional, mixed sliding–rolling than in reciprocating, sliding conditions. However, it is found that functionalised polymers and conventional organic and molybdenum-based friction modifiers can be combined to provide effective friction reduction over the whole range of rubbing conditions.     

羟基硅酸镁和MoDTC复合添加剂的减摩抗磨性能

采用MMW-1A型立式万能摩擦磨损试验机分别考察羟基硅酸镁超细粉体以及羟基硅酸镁超细粉体复合MoDTC作为基础油PAO4添加剂的摩擦学性能,借助金相系统显微镜、扫描电子显微镜(SEM)以及能量色散谱仪(EDS)对摩擦表面进行观察表征及组成分析。结果表明:羟基硅酸镁超细粉体可改善PAO4的减摩抗磨性能,但摩擦表面仍存在明显划痕及凹坑;质量分数0.25%的羟基硅酸镁超细粉体与0.3%的MoDTC组成的复合添加剂,可明显改善PAO4的减摩抗磨性能,相比于PAO4基础油和仅添加质量分数0.25%的羟基硅酸镁超细粉体的润滑油,摩擦因数分别降低了32.75%和17.87%,磨斑直径分别下降了53.16%和32.04%;复合添加剂对磨斑表面形貌的改善效果更为显著,其在摩擦表面形成了一层富含C、O、Mo、S、Mg、Si等元素的修复层,且2种添加剂在摩擦过程中优势互补,起到了相互促进的协同作用。     

低黏度0W-16汽油机油减摩性能研究

目的 研究低黏度0W-16机油的减摩性能。方法 选取3种减摩剂MoDTC、GMO和油酸酰胺,分别按一定比例加入到0W-16基础油中,获得单剂油样,并选取2种0W-16全配方机油（A-1油和A-2油）,利用SRV-IV试验机测试润滑油样的减摩性能和极压性能,利用傅立叶红外光谱仪和油料元素光谱分析仪分析机油油样结构,并利用3D光学表面轮廓仪表征缸套块磨痕形貌。结果 对于单剂油样,0W-16基础油分别加入MoDTC、GMO和油酸酰胺后,平均摩擦系数由0.198分别减小到0.088~0.116、0.167~0.178和0.179~0.194,缸套块磨痕平均深度由3.59 mm分别减小到0.44~0.52 mm、2.11~2.24 mm和3.19~3.44 mm。对于0W-16全配方机油,在摩擦润滑试验低温区,A-1油比A-2油摩擦系数低,随着温度升高,A-1油和A-2油的摩擦系数进一步减小;摩擦润滑试验后,A-1油和A-2油的缸套块磨痕平均深度分别为0.13 mm和0.18 mm。在极压试验中,A-1油和A-2油的极压值分别为1500 N和900 N。结论 在0W-16基础油中分别加入3种减摩剂后,MoDTC的减摩和抗磨作用最好,油酸酰胺的减摩和抗磨作用最差。对于0W-16全配方机油,在摩擦润滑试验低温区,A-1油中的无灰减摩剂和MoDTC产生协同作用,表现出更低的摩擦系数;随着温度升高,A-1油和A-2油中的ZDDP与MoDTC产生协同作用,进一步降低摩擦系数。在极压试验中,A-1油中的ZDDP与其他添加剂产生协同作用,表现出更大的极压值。添加剂之间的协同作用对油品节能性能产生重要影响。     

激光热喷涂Co30Cr8W1.6C3Ni1.4Si涂层在PAO+2.5%MoDTC油中摩擦学特性

为了提高TC4合金的耐磨性能,采用激光热喷涂技术在其表面制备了Co₃₀Cr₈W_1.6C₃Ni_1.4Si涂层。通过扫描电子显微镜（SEM）和X射线衍射（XRD）分析了涂层的形貌和物相,并通过摩擦磨损实验研究了涂层在PAO+2.5% MoDTC（质量分数）油中的磨损行为。结果表明,激光热喷涂的Co₃₀Cr₈W_1.6C₃Ni_1.4Si涂层主要由Ti、WC_1-x、CoO、Co₂Ti₄O和CoAl相组成,在涂层界面形成冶金结合。在激光功率为1000、1200和1400 W时所制备的涂层平均摩擦因数分别为0.151、0.120和0.171,其对应的磨损率分别为1.17×10^-6、1.33×10^-6和2.80×10^-6 mm³?N^-1?m^-1,磨损机理为磨粒磨损,其枝晶尺寸对降磨起主要作用。     

Tribological Properties of Phosphor Bronze and Nanocrystalline Nickel Coatings Under PAO + MoDTC and Ionic Liquid Lubricated Condition

The friction and wear properties of phosphor bronze and nanocrystalline nickel coatings were evaluated using a reciprocating ball-on-plates UMT-2MT sliding tester lubricated with ionic liquid and poly-alpha-olefin containing molybdenum dialkyl dithiocarbamate, respectively. The morphologies of the worn surfaces for the phosphor bronze and nanocrystalline nickel coatings were observed using a scanning electron microscope. The chemical states of several typical elements on the worn surfaces were examined by means of X-ray photoelectron spectroscopy. Results show that the phosphor bronze and nanocrystalline nickel coatings exhibited quite different tribological behaviors under different lubricants. Phosphor bronze plate shows higher friction coefficient (0.14) and wear rate (3.2 × 10⁻⁵ mm³/Nm) than nanocrystalline nickel coatings (average friction coefficient is 0.097, wear rate is 1.75 × 10⁻⁶ mm³/Nm) under poly-alpha-olefin containing molybdenum dialkyl dithiocarbamate lubricated conditions. The excellent tribological performance of nanocrystalline nickel coatings under above lubricant can be attributed to the formation of MoS₂ and MoO₃ on the sliding surface. a quite a number of C, O and F products on worn surface of phosphor bronze than NC nickel coatings can improve anti-wear properties while using ionic liquid as lubricant.     

摩擦化学反应对发动机油润滑耐久性能的影响

利用SRV高温摩擦磨损试验机比较了两种分别属于GF-2和GF-3等级，含有MoDTC摩擦改进剂的发动机油的耐久性。结果表明，由于GF-3等级发动机油能使活塞环和缸套试样表面更加平整光滑，且由于Ca清静剂与MoDTC／ZDTP的协同作用，通过摩擦化学反应，在摩擦表面形成良好的摩擦反应膜，从而使它拥有更好的润滑耐久性能。     

全配方发动机油SJ/5W-30中二烷基二硫代甲酸钼的磨擦学特性研究(Ⅰ)——二烷基二硫代甲酸钼(MoDTC)的减摩抗磨特性

以渗氮层/灰铸铁摩擦副为对象,采用全配方矿物基发动机油SJ/5W-30作为基础润滑油,研究了油溶性有机钼添加剂二烷基二硫代甲酸钼(MoDTC)在125℃、250℃和320℃三种不同温度下的摩擦学特性。结果表明:MoDTC添加至全配方发动机油SJ/5W-30中能有效降低摩擦系数以及渗氮层/灰铸铁摩擦副的磨损程度。而且,温度越高,MoDTC的减摩抗磨作用越显著。磨损表面的SEM观察表明:温度升高,渗氮层与灰铸铁的磨损程度均增大。添加剂MoDTC的存在能显著减缓温度对磨损程度的影响。     

全配方发动机油SJ/5W-30中二烷基二硫代甲酸钼的摩擦学特性研究(Ⅱ)--二烷基二硫代甲酸钼(MoDTC)的摩擦化学效应

EDX分析表明，摩擦磨损过程中二烷基二硫代甲酸钼(MoDTC)中的活性元素与摩擦副材料表面发生了摩擦化学反应。温度和摩擦机械作用能显著促进：MoDTC与摩擦表面的摩擦化学作用。MoDTC的存在促进了全配方发动机油SJ／5W-30中的多功能添加剂ZDTP的分解。采用添加MoDTC的油样润滑时，在铸铁磨损表面上能形成Mo的化合物(MoO3，MoS2)以及硫化物(FeS)；纯基础油样SJ/5W-30润滑时铸铁磨损表面上只有硫化物形成，而且所形成的硫化物除FeS之外，还有较多的硫酸盐(FeSO4)。MoDTC与ZDTP甲复配时边界反应膜的形成可采用Pearson的硬软酸碱(HSAB)原理来阐释。     

Evaluation of Local Mechanical Properties in Depth in MoDTC/ZDDP and ZDDP Tribochemical Reacted Films Using Nanoindentation

Local mechanical properties in depth and near the surface of MoDTC/ZDDP and ZDDP tribofilms, which exhibited obviously different friction coefficients in a pin-on-disc test, were determined by using a nanoindentation technique combined with in-situ atomic force microscopy (AFM) observation. Tapping-mode AFM observation revealed that the MoDTC/ZDDP film was much rougher than the ZDDP film. Nanoindentation measurement revealed that the MoDTC/ZDDP and ZDDP tribofilms possessed different elasto-plasticities around a depth of several nanometers from the surface, although both films showed the same hardness and modulus depth distributions except in the surface area. The same mechanical depth distributions indicated that both kinds of tribofilm were functionally graded materials; that is, they consisted of a layer near the surface with lower hardness and modulus and providing lubrication and a base layer with higher hardness and modulus and serving to modify property differences at the interface. Most importantly, the different elasto-plasticities near the tribofilm surfaces revealed that the MoDTC/ZDDP tribofilm possessed lower shearing yield stress than the ZDDP tribofilm. The results of this study suggest that the presence of some solid lubricants such as MoS₂ just below the MoDTC/ZDDP film surface reduced the boundary friction coefficient.     

二烷基二硫代甲酸钼(MoDTC)摩擦改进剂对GF-3等级全配方发动机油摩擦学性能的影响

利用SRV高温摩擦磨损试验机研究了二烷基二硫代甲酸钼(MoDTC)对渗氮活塞环／铸铁缸套在ILSACGF-3发动机油润滑条件下的摩擦学性能的影响。结果表明，MoDTC能与GF-3全配方发动机油中的ZDTP／磺酸钙添加剂体系产生协同作用，在活塞环和缸套表面生成减摩和抗磨的摩擦反应膜，从而显著降低并在较长时间内保持低摩擦系数(最低0．03)，同时缸套的磨损降低50％以上。