Laboratory evaluation of the dispersancy power of a gasoline engine oil and its relationship with sequence VE test results

The evaluation of the dispersancy power of a gasoline engine oil is included among such international specifications as those of the Committee of Common Market Automobile Constructors (CCMC) and the American Petroleum Institute (API). Such an evaluation is carried out by means of long, severe, and expensive engine bench tests, the engines used being Mercedes M102E (CCMC G4 and G5 levels) or the Ford Pinto 2.3 (API SG and SH levels). The cost of these tests necessitates pre-selection of oils by laboratory tests and these need to be a reliable indicator of bench test performance. The present study proposes two new laboratory methods, the OXYDISP and the POTDISP tests, which associate artificial ageing of the lubricants with modified blotter spots tests. These tests showed excellent correlation with Sequence VE engine test results. They were also capable of distinguishing oils of different API standards. They therefore provide an effective tool for preselection of lubricants, without pretending to be a replacement of or substitute for Sequence VE or other engine bench tests.     

New field and engine test data to demonstrate the wear protection benefits of a unique boundary chemistry (UBC)

The wear protection performance of unique boundary chemistry (UBC), both while in the engine and after removal, was tested with reference to commercial API SG, API SH/ILSAC GF-1, and API SJ/ILSAC GF-2 quality oils in two 80,450 km field tests, in modified and standard sequence tests, and in radiotracer engine studies. The radiotracer tests of UBC added to an API SJ/ILSAC GF-2 quality oil replicated previously published results of wear reductions achieved in a comparison of an API SH/ILSAC GF-1 oil with and without UBC. In extended Sequence IIIE runs, two engines, each lubricated with the same API SH/ILSAC GF-1 oil, were unable to complete the tests as a result of excessive oil consumption due to hot stuck rings. In contrast, two Sequence IIIE engines lubricated with the same API SH/ILSAC GF-1 oil treated with UBC completed the extended test without incident, even though the UBC-treated API SH/ILSAC GF-1 oil replaced the API SH/ILSAC GF-1 oil for the first oil drain interval only. A fully formulated SAE 5W–30 oil, which contained a full complement of UBC (20%), met all the requirements of API SH/ILSAC GF-1 quality and gave very low average and maximum cam and cam plus lifter wear on standard ASTM Sequence VE and IIIE tests. The same API SH/ILSAC GF-1 oil without UBC gave somewhat higher wear on both tests, but both oils met API SH/ILSAC GF-1 requirements. Wear metals analysis of a field test of 36 taxicabs, which compared an API SJ/ILSAC GF-2 quality oil to the same oil treated with UBC for the first drain interval, and also to a UBC-treated oil at every oil change, showed a reduction in the rate of used oil Fe accumulation for both methods of UBC treatment. This test also revealed a striking impact on Fe levels from Si found in used oil samples during an episode of Si contamination in local gasoline supplies. Finally, in a field test of 10 taxicabs, with parts measured before and after testing, wear reductions were observed in rings and bearings in UBC-treated cabs compared to those with API SG oil alone.     

An automated laboratory lubricant test to simulate valve train wear

The need for a laboratory tool to screen the antiwear properties of potential additives has become more crucial as engine tests have become more expensive and lubricant requirements have become more stringent. A laboratory test has been developed using the Falex machine to simulate the valve train wear of an automobile engine. The test procedure was 3.5 h long and included two levels of applied load. This laboratory test was found to give reproducible wear and correlated with the Sequence III-C engine wear test. The labor-intensive part of the test was converted to computer control and data acquisition. This conversion improved both test control and productivity.     

Experimental analysis of tribological properties of lubricating oils with nanoparticle additives

This study examined the tribological properties of two lubricating oils, an API-SF engine oil and a Base oil, with CuO, TiO₂, and Nano-Diamond nanoparticles used as additives. The friction and wear experiments were performed using a reciprocating sliding tribotester. The experimental results show that nanoparticles, especially CuO, added to standard oils exhibit good friction-reduction and anti-wear properties. The addition of CuO nanoparticles in the API-SF engine oil and the Base oil decreased the friction coefficient by 18.4 and 5.8%, respectively, and reduced the worn scar depth by 16.7 and 78.8%, respectively, as compared to the standard oils without CuO nanoparticles. In addition, investigations were performed using TEM, OM, SEM, and EDX to interpret the possible mechanisms of anti-friction and anti-wear with nanoparticles.     

合成基润滑油聚α-烯烃低温摩擦润滑性能研究

在低温条件下,润滑油黏度变大,流动性变差,添加剂活性降低,对润滑性能产生显著影响。为研究PAO润滑油的低温摩擦润滑性能,以不同黏度级别PAO基础油为研究对象,采用流变仪MCR302、SRV摩擦磨损试验机,研究PAO润滑油样及添加极压抗磨添加剂的油样在低温条件下的流变性能和磨损润滑性能。试验结果表明：在低温环境下,随着温度降低,PAO油样的黏度急剧增大,黏度越大的油样其受低温条件影响越明显;PAO油样在低温环境下,表现出明显的剪切稀化现象;低温环境使得极压抗磨剂添加剂的活性变低,添加剂并未表现出减摩抗磨作用。因此,低温试验条件对PAO基础油和添加剂的摩擦学性能产生显著影响,阻碍了基础油和润滑油添加剂减摩抗磨作用的发挥。     

Effect of a surface film on the friction and wear properties of plasma-sprayed Al2O3---40%ZrO2 coatings

In order to provide the replenishment of a surface film in high temperature lubrication, an in situ formed graphite film is very useful. In this work, five synthetic lubricants were employed to evaluate the effectiveness of graphite film generation on a ceramic coating under extreme conditions of high pressure and 320 °C. Combined lubrication of the liquid and solid film occurs, and a carbonaceous polymer is generated on the Al₂O₃---40%ZrO₂ coating. Because of combined lubrication, the friction coefficient decreases to 0.04 from about 0.5 for dry friction. The main wear mechanisms involved smearing and breaking off of the ceramic coating for high temperature lubrication. Zin dialkyldithiophosphate (ZDDP) plays an important role in the anti-wear performance of oils, and mainly smearing wear is observed on the coatings lubricated with ZDDP-containing oils.     

Zinc Dialkyldithiophosphate Additive Adsorption on Carbon Black Particles

Soot is known to cause high wear in engine components and this is a problem with engine oils between extended drain intervals. Although several wear mechanisms have been suggested, exact soot-induced wear mechanisms are still not fully understood. This study aims to investigate the additive adsorption mechanism (specifically anti-wear additive) on carbon black (CB) particles (as a soot surrogate). This mechanism is one of the main mechanisms responsible for high wear. Base oil (BO) was used to exclude the effect of other additives that are present in fully formulated oil. Zinc dialkyldithiophosphate (ZDDP) anti-wear additive was added to the BO and then the mixture, which will be referred to as the model oil, was aged with CB particles. The resulting oils were then chemically characterised by using ICP and FTIR analysis techniques. Finally, the CB particles were filtered out and analysed using EDX. The results showed that both zinc and phosphorous which are chemical elements from ZDDP anti-wear additive were adsorbed on CB particles in the oil phase. This additive adsorption mechanism can lead to increased wear in the engine components due to lack of additives in the oil. This study highlights the importance of understanding the additive adsorption on soot particles since this mechanism will reduce the engine oil life and increase frequency of oil changes.     

极压抗磨剂在GTL基础油中的感受性研究*

为探讨GTL基础油与常用极压抗磨剂感受性,分别将二烷基二硫代磷酸锌（T203）、磷酸三甲酚酯（T306）、二烷基二硫代氨基甲酸钼（S-525）、钼胺络合物（MOLYVAN 855）、硫磷酸复酯胺盐（T307）、硫化异丁烯（T321）和合成酯（VANLUBE 7723）与GTL基础油进行调配,利用四球摩擦试验机分别考察单剂和复配后油样的最大无卡咬负荷、磨斑直径和摩擦因数。结果表明：T307、MOLYVAN 855在GTL基础油中极压性和抗磨性最优;T203和VANLUBE 7723复配、T203和MOLYVAN 855复配对GTL基础油极压性和抗磨性能提升明显,而T203和S-525复配具有最佳的减摩效果;T306分别和S-525、T307和T321复配时表现出的极压性能变化趋势相似,而T306和T307复配在表现出良好极压性能的同时,兼具有较好的减摩抗磨效果。     

A study on wear and wear mechanism of exhaust valve and seat insert depending on different speeds using a simulator

The wear of engine valve and seat insert is one of the most important factors which affect engine performance. Because of higher demands on performance and the increasing use of alternative fuel, engine valve and seat insert are challenged with greater wear problems than in the past. In order to solve the above problems, a simulator was developed to be able to generate and control high temperatures and various speeds during motion. The wear simulator is considered to be a valid simulation of the engine valve and seat insert wear process with various speeds during engine activity. This work focuses on the different degrees of wear at three different singular test speeds (10 Hz, 25 Hz & multi-Hz). For this study, the temperature of the outer surface of the seat insert was controlled at 350°C, and the test load was 1960 N. The test cycle number was 6.0×10⁶. The mean (±standard error) wear depth of the valve at 10 Hz and 25 Hz was 45.1 (±3.7)μm and 81.7 (±2.5)μm, respectively. The mean wear depth of the seat insert at 10 Hz and 25 Hz was 52.7 (±3.9) μm and 91.2 (±2.7) μm, respectively. In the case of multi-Hz it was 70.7 (±2.4)/on and 77.4 (±3.8) μm, respectively. It was found that higher speed (25 Hz) cause a greater degree of wear than lower speed (10 Hz) under identical test condition (temperature, valve displacement, cycle number and test load). In the wear mechanisms of valves, adhesive wear, shear strain and abrasive wear could be observed. Also, in the wear mechanisms of seat inserts, adhesive wear, surface fatigue wear and abrasive wear could be observed.     

基于SRV的润滑油高温润滑性能测试方法的研究

为选择比较在高温工况条件下具有最佳摩擦磨损性能的润滑油,定量表征润滑油的极限工作温度和高温耐磨性能,提出一种润滑油的极限工作温度和高温耐磨性能测试方法。该方法通过磨损量和平均摩擦因数随温度的变化,来得到油品的极限工作温度,通过高温下pv值曲线来定量评定油品的高温工作性能。利用该方法对3种润滑油进行测试分析,并结合油品设计配方进行分析。结果表明,该方法可以简单、准确且定量的评定、比较润滑油的极限工作温度和高温耐磨性能。     

Anti‐wear performance of organomolybdenum compounds as lubricant additives

A four‐ball tester was used to evaluate the anti‐wear performance of three kinds of organomolybdemun compounds in engine oils and lithium soap grease, i.e. molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate (MoDTC), and sulphur‐ and phosphorus‐free organomolybdeum (molybdate). The results indicate that a low concentration of MoDDP does not improve the anti‐wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti‐wear properties of the engine oils. MoDTC does not improve the anti‐wear properties of the engine oils, but worsens the anti‐wear properties of the oils. Significant improvement of the anti‐wear properties is obtained with molybdate added in the four fully formulated oils. Both MoDDP and molybdate have good anti‐wear properties in the lithium soap grease, especially MoDDP with a high concentration. Copyright © 2006 John Wiley & Sons, Ltd.     

Silver-Organic Oil Additive for High-Temperature Applications

Modern lubricants face the task of providing lubrication over a wide range of temperatures, and extreme engine temperatures can exceed the thermal degradation limits of many engine oils. Soft metal additives can extend the life of engine oils at very high temperatures by providing solid lubrication to contacting surfaces. We report a new silver–organic complex which contains a high metal content and minimal supporting organic ligands. This silver pyrazole–pyridine complex is evaluated as a friction-reducing and anti-wear additive in engine oil at testing temperatures which thermally degrade the base oil. Two sets of ball-on-disk tests are performed: the first at a constant temperature of 200 °C and the second while increasing the chamber temperature from 180 to 330 °C. At 200 °C, the wear is considerably reduced compared with the base oil when the silver-organic additive is present at 2.5–5.0 wt%. Furthermore, the silver-based additive at 20 wt% in oil induces a remarkable friction reduction during the temperature ramp test, so much, so that the tribological transition from the oil as the primary lubricant to its degradation, and to the silver additive as the primary lubricant, is imperceptible.     

Anti-wear Chemistry of ZDDP and Calcium Borate Nano-additive. Coupling Experiments, Chemical Hardness Predictions, and MD Calculations

Zinc dialkyl dithiophosphate (ZDDP) is an anti-wear additive for steel surfaces currently used in engine oils. Its anti-wear performance (against abrasion) is due to tribochemical reaction of zinc polyphosphate with abrasive metal oxides nanoparticles, under the combined effect of pressure and shear. However, phosphorous and sulfur are nocuous for environmental issues. Borates are possible candidates to replace phosphates in engine oils. Friction reduction with borates is found to be better than ZDDP but the anti-wear efficiency of borates is lower. In this work, we show how chemical hardness model and computer simulation can explain these different behaviors. Also we show that molecular dynamics is able to predict accurately behavior of mixtures of phosphates and borate. Results show that mixtures of additives with a P:B ratio slightly above unity can be a good compromise to have both good tribological performance and low content of phosphorous and sulfur in the lubricant.     

柴油机滑动轴承磨损试验系统的开发与研制

针对柴油机轴瓦磨损问题,为了研究滑动轴承磨损影响机理且由于现有设备无法满足试验要求,开发研制了一套滑动轴承磨损试验系统。利用该系统可进行主轴瓦和连杆瓦两种滑动轴承在结构、转速、载荷、磨粒、润滑油状态不同条件下磨损状态的模拟试验研究。在完成试验方法研究的基础上,着重介绍了该试验系统的液压模块、机械承载模块、润滑模块、试验控制模块等子系统的开发设计。该系统采用液压伺服的加载方式对模拟轴进行了拉压加载,采用变频器控制驱动电机转速,润滑油的压力及温度可以自由调节,并利用基于美国NI公司的LabVIEW环境的软件实现了对试验系统的自动控制以及试验数据实时显示和存储,实现了不同工况下的轴瓦磨损的模拟试验。研究结果表明,该试验系统可以实现试验功能,具有良好的试验性能,达到了试验系统开发的预期目标。     

不同氧化条件下柴油机油的氧化降解研究

为探讨氧化温度、时间以及金属催化氧化等因素对柴油机油性能的影响,采用高温烘箱以及氧化测试仪模拟不用的氧化条件,研究柴油机油氧化前后部分理化性能、摩擦学性能的变化,分析不同氧化条件对柴油机油的氧化过程及性能的影响规律.结果表明:高温烘箱试验后发动机油的理化性能、抗氧化性能以及摩擦学性能会有一定程度的劣化,但变化幅度不大,...     

The decomposition products of zinc dialkyldithiophosphate in an engine and their interaction with diesel soot

Japanese valve train wear engine tests were carried out using oils containing a common zinc dialkyldithiophosphate (ZnDTP). The ZnDTP decomposition products formed in the oils during the engine tests were analysed. It was found that the ZnDTP decomposition results in the formation of zinccontaining compounds and phosphorus-containing intermediate products such as tetraalkylthioperoxidiphosphate. During an engine test, the ZnDTP decomposes rather quickly, whereas the phosphorus-containing intermediate products were detected over a long period. The adsorption test results indicate that diesel soot adsorbs the zinc compounds but that the soot adsorbs little of the phosphorus compounds. From the valve train wear test results and four-ball wear test results it was found that the oils tested in the engine keep their antiwear performance after the ZnDTP has decomposed and that this performance is mainly attributable to the phosphorus-containing compounds.     

Antiwear Behavior of ZDDP and Fluorinated ZDDP in the Presence of Alkylated Diphenyl Amine Antioxidants

Environmental regulations have called for a reduction of phosphorus content in engine oils in recent years. The anti-wear additive zinc dialkyl dithiophosphate (ZDDP), which is also an antioxidant, is one of the most important components of engine oil additives. ZDDP is a major source of phosphorus. One way to reduce phosphorus levels is to replace ZDDP with new environmentally friendly antiwear agents that have similar or superior wear performance compared to ZDDP. Another way to address the environmental issue is to reduce the amount of ZDDP in engine oils. At the same time, it is necessary to increase the efficiency of ZDDP by finding optimum conditions that would result in improved antiwear performance. The antiwear mechanism of ZDDP involves its degradation thermally and tribologically, leading to the formation of an antiwear film that consists of polyphosphates and sulphides. The structure of the antiwear film is almost similar in both types of degradation. But the breakdown efficiency of ZDDP is diminished by the parallel reaction of ZDDP with other additives, as well as the antagonistic effects of these additives. The new fluorinated ZDDP complex developed has shown better wear performance compared to ZDDP. This would allow the possibility of further reduction of phosphorus in engine oils compared to current levels. In this paper we study the interaction of ZDDP and fluorinated ZDDP with alkylated diphenylamine. The impact of antioxidant on wear performance was examined using a ball-on-cylinder tribometer. The interactions between ZDDP and the fluorinated ZDDP with the antioxidant were studied using NMR and the surface of the tribofilm was examined using SEM, TEM, and Auger spectroscopy.     

HM抗磨液压油的加水磨损性能试验研究

介绍了HM抗磨液压油做了小型台架加水磨损试验研究，对两种油品进行初步评测。     

Modeling of Abrasive Wear in a Piston Ring and Engine Cylinder Bore System©

Engine-related improvements such as more efficient engine components, improved engine oils, and high-performance coating materials, need to be verified in terms of their effects on the tribological performance of the piston ring/cylinder bore system. The main purpose of this research is to develop an abrasive wear model for the piston ring/cylinder bore system during steady-state operation by considering the effects of temperature, load, oil degradation, surface roughness, and material properties. The model can be used either in theoretical modeling or integrated with finite element analysis. Based on a laboratory simulator, a three-body abrasive wear model has been developed to model the wear progression of the piston ring/cylinder bore system during steady state operation. The proposed novel abrasive wear model addresses the effects of temperature, load, oil degradation, surface roughness, and material properties. The feasibility of the proposed model is illustrated by a numerical example.     

用SRV试验机评价柴油机油摩擦磨损性能

采用SRV^?4型摩擦磨损试验机为试验平台,以某商用车公司提供的发动机缸套-活塞环截取件作为摩擦副试验件,以15W-40 CF-4和15W-40 CI-4发动机油为润滑介质,建立评价柴油机油摩擦磨损性能的模拟试验方法,并使用该方法对油品配方中减摩剂的区分性及不同材质活塞环与润滑油的适配性等进行考察。试验结果表明:建立的模拟试验方法能较好地区分出具有优异抗磨性能的柴油机油,同样对油品配方中减摩剂和不同材质活塞环与润滑油适配性等有着较好的区分性,可以作为润滑油品开发者和OEM汽车厂家对油品配方开发和摩擦副材质筛选的模拟评价手段。