Antiwear,Antifriction, and Extreme Pressure Properties of Motor Bike Engine Oil Dispersed with Molybdenum Disulfide Nanoparticles

This work presents studies on the antiwear, antifriction, and extreme pressure properties of motor oil dispersed with MoS₂ nanoparticles. Commercial oil (SAE 20W-40 grade) is dispersed with stabilized MoS₂ nanoparticles in 0.25, 0.5, 0.75, and 1 wt%. The test oils are tested for antiwear, antifriction, and extreme pressure properties on a four-ball wear tester. The wear and friction offered by nanolubricants has decreased remarkably compared to the commercial base oil. The weld load and load wear index of oils dispersed with nanoparticles were improved substantially compared to the commercial base oil. Metallographic studies conducted on the wear balls from the extreme pressure test show that nanoparticles are deposited on the worn area along with additives in the oil, thereby preventing welding of the surfaces. An optimum weight fraction is arrived at for best performance. A synergy between the additives in the oil and dispersed nanoparticles has been observed, resulting in less dispersion for best results. It is found that beyond an optimum weight percentage of nanoparticles, the trends tend to reverse, resulting in greater wear and friction.     

Tribological Performance and Mechanism of Phosphate Ionic Liquids as Additives in Three Base Oils for Steel-on-aluminum Contact

Butylammonium dibutylphosphate and tetrabutylammonium dibutylphosphate ionic liquids (ILs) were evaluated as antiwear additives for steel-on-aluminum contact in three different base oils, a polyalphaolefin, an ester oil and an IL 1-methy-3-hexylimidazolium hexafluorophosphate, respectively, with similar viscosity and different polarities. The friction experiments were carried out on an Optimal SRV-IV oscillating reciprocating friction and wear tester at room temperature. Results indicate phosphate ILs can effectively improve the tribological properties of the base oil, especially the antiwear property, as additives for steel/aluminum contacts. For the base oils PAO10 and PAO40 with different viscosities, the higher viscosity of PAO40 can be beneficial to reducing the friction coefficient. The worn surface morphologies and chemical compositions of wear scars were analyzed by a JSM-5600LV scanning electron microscope and PHI-5702 multifunctional X-ray photoelectron spectrometer (XPS). The XPS analysis results illustrate that the phosphate IL additives in the base oils with different polarities exhibit the same tribological mechanism. A synergy exists between the adsorbed layers and boundary-lubricating films generated from the tribochemical reaction of IL and the substrate surface, which may reduce the friction coefficient and wear volume of the friction pairs.     

Friction Reduction and Antiwear Capacity of Engine Oil Blends Containing Zinc Dialkyl Dithiophosphate and Molybdenum-Complex Additives

The efficacy of oil blends containing zinc dialkyl dithiophosphate (ZnDTP) and molybdenum (Mo)-complex additives to improve the tribological properties of boundary-lubricated steel surfaces was investigated experimentally. The performance of oil blends containing three different types of Mo-complex additives of varying Mo and S contents with or without primary/secondary ZnDTP additions were investigated at 100°C. The formation of antiwear tribofilms was detected in situ by observing the friction force and contact voltage responses. Wear volume and surface topography measurements obtained from surface profilometry and scanning electron microscopy studies were used to quantify the antiwear capacity of the formed tribofilms. The tribological properties are interpreted in terms of the tribofilm chemical composition studied by X-ray photoelectron spectroscopy. The results demonstrate that blending the base oil only with the Mo-compound additives did not improve the friction characteristics. However, an optimum mixture of Mo complexes and ZnDTP additive provided sufficient amounts of S and Mo for the formation of antiwear tribofilms containing low-shear strength MoS ₂ that reduces sliding friction. In addition, the formation of a glassy phosphate phase due to the synergistic effect of the ZnDTP additive enhances the wear resistance of the tribofilm. This study shows that ZnDTP- and Mo-containing additives incorporated in oil blends at optimum proportions improve significantly the tribological properties of boundary-lubricated steel surfaces sliding at elevated temperatures.     

Antiwear Properties of Phosphorous-Containing Compounds in Vegetable Oils

Antiwear properties of vegetable oils were investigated under boundary lubrication conditions using the four-ball wear test (ADTM D 4172). Additive-free vegetable oils exhibit similar antiwear properties, which are superior to those of additive-free mineral oils. Phosphorus-containing compounds such as zinc bis(dialkyldithiophosphate) and dialkyl phosphonates improve the antiwear properties of vegetable oils. The effect of the additives on wear reduction was found to depend on the peroxide value of the base oil. It is considered that peroxides decompose the antiwear additives to less active forms. The formation of peroxides by the autooxidation of vegetable oils was observed even at room temperature. Sunflower oil exhibits good oxidation stability, which may promise success in various applications.     

抗磨添加剂对不同服役阶段润滑油摩擦学性能的影响

采用黏度测试仪测定新油及3种不同服役阶段润滑油的黏度,采用UMT-II摩擦磨损试验机考察其摩擦学性能,并同时考察3种在用润滑油添加抗磨添加剂后的摩擦学性能。研究结果表明:润滑油的黏度随着运行里程数的增加呈现先降后增的趋势;随润滑油运行里程数的增加,润滑油的摩擦因数增大,导致试验钢球的磨损量也增加;抗磨添加剂对不同服役阶段的润滑油的抗磨性能影响程度不同,在磨合磨损期和正常磨损期,加入抗磨添加剂后并不能改善润滑油的抗磨性能,而在异常磨损期,抗磨添加剂的加入可较好地改善润滑油的抗磨性能。     

硫、磷系添加剂复合使用在菜籽油中的抗磨性能研究

以菜籽油为基础油，在四球摩擦磨损实验机上分别考察丁两组硫系和磷系添加剂T321与T304、T321与T307复合使用对菜籽油的抗磨性和极压性的影响。结果表明，在菜籽油叶：加入添加剂T321与T304能更好地提高菜籽油的抗磨性能和极压性能。     

油溶性CuO纳米颗粒的抗磨性能研究

利用四球摩擦磨损实验机考察了油酸铜修饰CuO纳米颗粒作为润滑油添加剂的抗磨性能,并用扫描电子显微镜（SEM）和X-射线光电子能谱（XPS）等对钢球磨损表面进行了分析。摩擦磨损试验结果表明,当添加质量分数仅为0.025%时,油酸铜修饰CuO纳米颗粒作为润滑油添加剂即能够明显提高基础油的抗磨能力。SEM及XPS分析结果表明,油酸铜修饰CuO纳米颗粒作为润滑油添加剂在摩擦过程中形成了一层富含Cu2O和Fe2O3的化学反应膜,正是这层膜的存在使得其表现出良好的抗磨性能。     

几种羟基脂肪酸在菜籽油中的润滑行为研究

利用四球摩擦磨损试验机,考察了实验室合成的几种羟基脂肪酸在菜籽油中的减摩抗磨和极压性能。试验结果表明：这些含氧添加剂具有一定的减摩抗磨能力,但对菜籽油的极压性能的没有影响。双羟基脂肪酸比单羟基脂肪酸的减摩抗磨效果更为明显;烷基链较长的羟基甘二酸比羟基十八酸的减摩抗磨性能略好。     

一种硫磷氮衍生物在菜籽油中的摩擦学研究

通过Mann ich合成了2种有机环胺的硫磷酸酯衍生物,在四球摩擦磨损试验机上研究了它们作为菜籽油添加剂的摩擦学性能。实验结果表明,该类化合物具有良好的极压抗磨性能,能提高菜籽油的极压抗磨性能。通过用X-射线光电子能谱(XPS)分析了钢球磨损表面典型元素的化学状态,显示在摩擦过程中,钢球表面形成了一层含硫、磷无机膜和含氮的有机膜。     

Comparison of boundary lubrication films formed under four‐ball friction test conditions with different AW/EP Additives‐an X‐ray photoelectron spectroscopy study

The antiwear and extreme‐pressure properties of six different types of additive (molybdenum dialkyldithiophosphate, dibenzyl disulphide, molybdenum dialkyldithiocarbamate, zinc dialkyldithiophosphate, chlorinated paraffin wax, and triaryl phosphate) were evaluated by standard four‐ball friction and wear tests. This was followed by scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), and X‐ray photoelectron imaging (XPI) analyses of the worn surfaces to determine the structure of the boundary lubrication film and the mechanism of the tribochemical reaction occurring during the friction process. The presence of the additives in the base oil significantly increased the weld load and drastically reduced the wear‐scar diameter, suggesting antiwear and extreme‐pressure properties of the additives. The enhanced antiwear and loadcarrying capacity of the additive‐containing oils was attributed to the formation of a complex boundary lubrication film formed between the surfaces during the friction process as a result of the tribochemical reaction. The antiwear and extreme‐pressure properties of the additives were explained based on the XPS data. The studies indicated that the lubricating properties of the additives depend on their chemical nature and reactivity with metal surfaces.     

苯并三氮唑羧酸衍生物和磷酸三丁酯的摩擦学协同性能

合成了一种新型无磷苯并三氮唑衍生物（BTB），利用四球摩擦磨损试验机考察了单剂BTB、磷酸三丁酯（TBP）以及不同配比的BTB和TBP的复合添加剂在液体石蜡中的摩擦磨损性能；用带散射能谱的扫描电镜分析了磨损表面形貌和元素分布。结果表明：所合成的BTB添加剂能提高基础油的承栽能力和减摩、抗磨性能，并且与TBP具有协同作用；在摩擦过程中发生物理、化学吸附的同时，与金属表面发生摩擦化学反应，生成一层复合膜，从而起到了极压抗磨作用。     

含硼复合抗磨剂的摩擦学特性研究

含硼和不含硼两种新型减摩抗磨挤的摩擦学性能用四球和环－圆柱试验机进行了研究,试验结果表明,含硼抗磨降低油品的摩擦系数,减少磨损的性能更明显,并在实际行车试验中表现出良好的抗磨性能。     

Tribological properties of phosphate esters as additives in rape seed oil

With the growing concern about environmental pollution, vegetable oils have begun to be applied as base oils for environmentally friendly lubricants. Additives containing phosphorus can be used for their excellent antiwear properties and low toxicity. In view of this, a study of a series of phosphate esters as additives in rape seed oil (RSO) was carried out using a four‐ball tester. The results indicate that phosphate esters possess very good load‐carrying capacity and good antiwear and friction‐reducing properties compared with RSO by itself. Surface analysis of the worn balls was carried out using X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The tribological mechanism of the additives is discussed on the basis of the experimental results.     

Low sulfur,phosphorus and metal free antiwear additives: Synergistic action of salicylaldehyde N(4)-phenylthiosemicarbazones and its different derivatives with Vanlube 289 additive

With a view to develop metal free, low SAPs antiwear additives, the antiwear properties of salicylaldehyde N(4)-phenylthiosemicarbazone and its p-methylphenyl, p-methoxyphenyl and p-chlorophenyl derivatives(1%w/v) and their synergistic/antagonistic behavior with Vanlube 289(1%w/v) additive were tested in base oil using four-ball lubricant tester and ZDDP as a reference additive. Antiwear testing of additives(1%w/v) was done by varying load and time. The performance of antiwear additives has been compared on the basis of tribological parameters. An appreciable synergistic activity is observed between 1% concentrations of the thiosemicarbazones and Vanlube289. The efficiencies of the synergistic formulations are far better than that of ZDDP. The topography and composition of the wear scar were analyzed by AFM and SEM with EDX. The synergistic formulations cause enormous reduction in surface roughness. The EDX analysis of the wear scar in the case of base oil with additive exhibits presence of sulfur and nitrogen.     

Effectiveness of Selected CHO Compounds as Antiwear Additives to White Mineral Oils

The objective of this article is to verify the effectiveness of CHO products (mixtures of esters) and their compositions with a lactam-type CHNO compound applied at the concentration ≤1 wt% as antiwear additives to white oils. The research was performed using a ball-on-disk tester and a special four-ball apparatus. The tested CHO and CHNO additives show very good antiwear properties under boundary lubrication conditions. They provide the highest wear reduction when they are introduced at 0.1 wt%. The wear reduction synergism for mixtures comprising 20 wt% of the CHNO compound and 80 wt% of the selected esters is not observed. Additionally, the limiting pressure of seizure, p_s, was determined. It was found that p_s is not improved by esters and the CHNO additive if they are added at 0.1 wt%; the positive influence of some mixtures comprising 20 wt% of the CHNO compound and 80 wt% of the chosen esters is revealed. It was also proved that the oil viscosity influences the tribological properties of applied additives under boundary lubrication and extreme pressure conditions.     

Study the Sensitivity of Solid Lubricating Additives to Attapulgite Clay Base Grease

The focus of this study was the development of a new lubricating grease, using surface-modified attapulgite clay as thickener and synthetic oil (PAO 40) as the base oil. The tribological sensitivity of the new grease was investigated by studying the effect of adding three solid additives [KB₃O₅, MoS₂, graphite and a graphite/MoS₂ mixture (mass ratio 3:2)]. Its tribological behavior was compared with that of traditional bentone grease by adding MoS₂. The dropping point and the cone penetration of the new grease were also investigated and analyzed. The wear scar diameter of the base grease was measured on an MRS-1 J (G) four-ball tester, and the tribological sensitivity of solid lubricating additives to attapulgite clay base grease was evaluated using an Optimol SRV reciprocating friction and wear tester. The addition of MoS₂ and the graphite/MoS₂ mixture to the new lubricating grease improved its friction-reducing ability, while the addition of KB₃O₅ improved its antiwear ability. The additives MoS₂ and the graphite/MoS₂ mixture also increased the load-carrying capacity of the base grease. The attapulgite clay grease containing MoS₂ had a better friction-reducing ability than the traditional bentone grease containing MoS_2.     

Friction‐reducing and antioxidant capabilities of engine oil additive systems under oxidative conditions. II. Understanding ligand exchange in a molybdenum dialkyldithiocarbamate/zinc dialkyldithiophosphate additive system in various base oils

The ligand‐exchange reactions between molybdenum dialkyldithiocarbamate, Mo(dtc)₂, and zinc dialkyldithiophosphate, Zn(dtp)₂, have been investigated during inhibited oxidation in a model hydrocarbon (hexadecane) and in a series of Group I–IV base oils at 160°C. These investigations revealed that the ligand exchange leads to formation of single‐exchange products, Mo(dtc)(dtp) and Zn(dtp)(dtc), and double‐exchange products, Mo(dtp)₂ and Zn(dtc)₂, and that the extent of the exchange is significantly affected by oxidation and inhibition reactions involving the original additives, the ligand‐exchange products, the base oil, and base oil‐derived oxidation products. It is concluded that there are two reaction sequences that control the product distribution and additive consumption during oxidation in different base oils. The first sequence involves the formation of peroxy radicals and hydroperoxides, and the decomposition of hydroperoxides by Zn(dtp)₂ and Zn(dtp)(dtc). One of the most important factors affecting this sequence is the base oil oxidisability. The second sequence involves inhibition of oxidation by peroxy radical‐trapping antioxidants naturally present in or added to the oil, or formed during the oxidation. Zn(dtc)₂ and Zn(dtp)(dtc) appear to be very effective in this respect and are, therefore, preferentially consumed. This preferential consumption shifts the ligand‐exchange equilibrium towards the formation of Mo(dtc)(dtp) and Mo(dtp)₂. The combined effect of the two sequences depends on base oil properties. The first sequence predominates in base oils exhibiting high oxidisability (e.g., in Group I oils) and the second in paraffinic oils, such as Group III and IV oils, having low oxidisability and no sulphur or aromatics. the retention of friction‐reducing capability with the Mo(dtc)₂/Zn(dtp)₂ additive system during oxidation appears to be tied to the first sequence, which leads to consumption of Zn (dtp)₂, since the friction‐reducing capability ceases when Zn (dtp)2 is consumed and hydroperoxides can accumulate in the system. Consequently, the best retention of friction‐reducing capability is achieved in bases oils with low oxidisability.     

Erratum to: Study the Sensitivity of Solid Lubricating Additives to Attapulgite Clay Base Grease

The focus of this study was the development of a new lubricating grease, using surface-modified attapulgite clay as thickener and synthetic oil (PAO 40) as the base oil. The tribological sensitivity of the new grease was investigated by studying the effect of adding three solid additives [KB₃O₅, MoS₂, graphite and a graphite/MoS₂ mixture (mass ratio 3:2)]. Its tribological behavior was compared with that of traditional bentone grease by adding MoS₂. The dropping point and the cone penetration of the new grease were also investigated and analyzed. The wear scar diameter of the base grease was measured on an MRS-1 J (G) four-ball tester, and the tribological sensitivity of solid lubricating additives to attapulgite clay base grease was evaluated using an Optimol SRV reciprocating friction and wear tester. The addition of MoS₂ and the graphite/MoS₂ mixture to the new lubricating grease improved its friction-reducing ability, while the addition of KB₃O₅ improved its antiwear ability. The additives MoS₂ and the graphite/MoS₂ mixture also increased the load-carrying capacity of the base grease. The attapulgite clay grease containing MoS₂ had a better friction-reducing ability than the traditional bentone grease containing MoS_2.     

Development and testing of nano particulate lubricant for worm gear application

Bio-degradable lubricants are an attractive alternative for the mineral based and synthetic based lubricants. Bio-degradable lubricants are environmental-friendly and non-toxic. The present study deals with the tribological investigation of bio-degradable nano lubricants for worm gear applications. Nano additives like CuO and TiO₂ were used. Bio-degradable oils like palm oil and sunflower oil were used as base oils. The nano lubricants were prepared by adding two nano additives and two bio-degradable oils each of 0.1 % and 0.2 % weight composition. Friction and wear characteristics were tested on pin-on-disc tribometer under varying load conditions. Extreme pressure tests for nano lubricants were carried out using four ball tester. The wear surface obtained was analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy. From the tests conducted, it was found that the addition of nano additives in biodegradable oils reduced the friction co-efficient and wear rate to a considerable extent.

     

Tribological behaviour of antiwear additives used in hydraulic applications: Synergistic or antagonistic with other surface-active additives?

This paper examines the friction and antiwear (AW) properties using SRV (Schwing–Reib–Verschleiss) tribometer and film-forming properties using atomic force microscope (AFM) of one simple model formulation containing solely AW additive and seven oils containing mixture of additives including three zinc-based packages (ZP), ZP with additional AW additives, ZP with extreme pressure (EP) additives, ZP with viscosity index improvers (VII) and one zinc-free ashless package in steel/steel contacts. VII-containing oil show lower boundary and mixed friction coefficients than the other oils. Although all AW additive-containing oils formed tribofilms, AW properties of ZPs appear to be affected antagonistically by EP additives while synergistically by VII. Zn-free additives investigated in this study show higher wear than ZPs.