Effect of Bio-Lubricant and Biodiesel-Contaminated Lubricant on Tribological Behavior of Cylinder Liner–Piston Ring Combination

This article addresses the issue of friction and wear characteristics of diesel engine cylinder liner–piston ring combinations under different lubricating conditions using a pin-on-disc wear tribometer. The discs were made out of actual engine cylinder liner material using a casting process. Pins were made out of top compression ring material. The tests were conducted on a pin-on-disc tribometer for wear and friction characteristics of the cylinder liner and piston ring combination with diesel-contaminated rapeseed oil–based bio-lubricant, diesel-contaminated commercial synthetic lubrication oil (SAE 20W40), biodiesel-contaminated commercial synthetic lubrication oil (SAE 20W40), and used (150 h) commercial synthetic lubrication oil (SAE 20W40). Experimental results demonstrated that the rapeseed oil–based bio-lubricant and biodiesel-contaminated synthetic lubricant exhibited better performance in terms of wear, friction, and frictional force under similar operating conditions. Thus, usage of newly formulated bio-lubricant and biodiesel in the long run may have a positive impact on engine life.     

Feasibility of Observing Small Differences in Friction Mean Effective Pressure between Different Lubricating Oil Formulations Using a Small,Single-Cylinder Motored Engine Rig

The feasibility of using a motored single-cylinder 517 cc diesel engine to observe small frictional differences between oil formulations is investigated. Friction mean effective pressure (FMEP) is measured and compared for an SAE 10W-30 and an SAE 5W-20 oil in three stages of production: base oil, commercial oil without a friction and wear reducing additive, and fully formulated commercial oil. In addition, a commercial SAE 5W-30 engine oil is investigated. Friction mean effective pressure is plotted versus oil dynamic viscosity to compare the lubricant FMEP at a given viscosity. Linear regressions and average friction mean effective pressure are used as a secondary means of comparing FMEP for the various oil formulations. Differences between the oils are observed with the base oil having higher friction at a given viscosity but a lower average FMEP due to the temperature distribution of the test and lower viscosities reached by the base oil. The commercial oil is shown to have both a higher FMEP at a given viscosity and a higher average FMEP than the commercial oil without a friction and wear reducing additive. The increase in friction for the oil without a friction and wear reduction additive indicates that the operational regime of the engine may be out of the bounds of the optimal regime for the additive or that the additive is more optimized for wear reduction. Results show that it is feasible to observe small differences in FMEP between lubricating oil formulations using a small, single-cylinder motored engine.     

Lubricating oil influence on exhaust hydrocarbon emissions from a gasoline fueled engine

Engine exhaust hydrocarbon emissions have been investigated for different lubricating oils, using gasoline as fuel. Six samples of lubricants have been tested: synthetic SAE 5W30 and SAE 5W40, semi-synthetic SAE 15W40 and SAE 20W50, and mineral SAE 15W40 and SAE 20W50. Experiments were carried out in a production engine mounted on a bench test dynamometer, varying engine load and speed in the range from 1500 to 6000 rev/min. The results demonstrate the influence of lubricant viscosity and base oil on hydrocarbon emissions. The synthetic oils showed the lowest hydrocarbon emission levels, especially in the low engine speed range.     

纳米二硫化钼作为润滑油添加剂的摩擦学性能研究

研究纳米二硫化钼作为润滑油添加剂的摩擦学性能。以不同的表面活性剂和不同的超声波分散时间制备纳米二硫化钼润滑油,考察表面活性剂和超声波分散时间对纳米二硫化钼分散稳定性的影响。采用四球机和描电镜考察纳米二硫化钼在润滑油中的摩擦学性能。结果表明,2%油酸表面活性剂和超声波分散30 min可有效提高纳米二硫化钼在润滑油中的分散稳定性,纳米二硫化钼在润滑油中具有良好的抗磨性能、减摩性能,特别是0.01%二硫化钼在润滑油中的抗磨性能和高负荷下的减磨性能更为突出。     

分散剂对有机粘土润滑油摩擦学性能的影响

以30#机械油为基础油,以0.4%季铵盐修饰有机粘土为添加剂,5%低碱值合成磺酸钙和5%聚异丁烯双丁二酰亚胺为分散剂,制备了几种分散剂优化的有机粘土润滑油。采用OPTIEN2120型紫外/可见分光光度计对分散剂的分散效果进行了检测;在M-200和MS-800型摩擦磨损试验机上,分别对不同分散剂作用下的有机粘土润滑油的减摩抗磨性能和承载能力进行了测试。分散效果检测表明分散剂可有效控制粘土微粒的粒径,阻止粘土微粒的团聚,使得粘土微粒在基础油中有良好的分散稳定性。摩擦磨损试验表明:分散剂能改进有机粘土润滑油的摩擦学性能,其中2.5%低碱值合成磺酸钙与2.5%聚异丁烯双丁二酰亚胺分散剂复配使用时有机粘土润滑油的摩擦学性能最佳;分散剂的加入在一定程度上能够提高有机粘土润滑油的承载能力。     

Friction and Wear Reduction Mechanism of Polyalkylene Glycol-Based Engine Oils

Polyalkylene glycols (PAG) have been explored as a possible base stock for engine oil formulation. The friction, wear, and load-carrying capacity of five different PAG chemistries were evaluated either as a base stock or as formulated oils in pure sliding and sliding-rolling conditions using various laboratory bench test rigs operating under boundary and mixed lubrication regimes. The results were compared against GF-5 SAE 5W-20 and a mineral-based oil. The wear surfaces were also characterized using various surface-sensitive techniques for analysis of tribofilms to understand the mechanism of friction reduction. The results indicated that PAG oils show lower friction/traction coefficients and improved load-carrying capability, depending on the formulation, than those of the GF-5 SAE 5W-20 and mineral-based oil. The adsorption of PAG molecules on the surface appeared to be responsible for the lower friction characteristics.     

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.

     

An assessment of beeswax as a thickener for environmentally friendly lubricating grease production

Environmentally friendly lubricants are preferred in many applications where groundwater or soil pollution is possible. The main purpose of the current study was to evaluate the possibility of beeswax use as a thickener for lubricating greases. European beeswax was used as a thickening material for the preparation of lubricating greases. Rapeseed oil and two mineral oils were used as base oils. The consistency, dropping point temperature, and tribological properties of the prepared lubricating greases were investigated and compared with conventional soap‐thickened greases. The prepared greases exhibited good tribological properties, especially the rapeseed‐oil‐based grease. However, tribological properties of conventional lubricating grease were superior to prepared ones. The weakness of the prepared lubricating greases is their narrow working temperature range. However, the beeswax together with rapeseed oil has great potential in the production of environmentally friendly, completely renewable lubricating greases. Copyright © 2014 John Wiley & Sons, Ltd.     

Tribological Analysis of a Hydrodynamic Journal Bearing under the Influence of Synthetic and Biolubricants

This study investigated the tribological characteristics of journal bearings exclusively for automotive applications under the influence of a synthetic lubricant (SAE20W40) and chemically modified rapeseed oil (CMRO) as a biolubricant, dispersed with TiO₂, WS₂, and CuO nanoparticles used as antiwear additive. The effects of synthetic and nanobased biolubricants on the tribological behavior of the hydrodynamic journal bearing were examined using a journal bearing test rig by measuring the coefficient of friction, oil film thickness, and wear under a load of 10 kN and a speed of 3,000 rpm. The test results show that CuO nanoadditives that are added to the biolubricant exhibit outstanding wear and friction reduction behavior, better than that with synthetic lubricants as well as other nanobased biolubricants. The inclusion of CuO nanoparticles in the biolubricant decreased the coefficient of friction by 27% and wear by about 47% compared to a synthetic lubricant. Additionally, investigations were performed using atomic force microscopy (AFM) and scanning electron microscopy (SEM) to study the surface morphology and surface roughness behavior of the tested bearing surfaces.     

Friction torque of thrust ball bearings lubricated with wind turbine gear oils

Planetary gearboxes used in wind turbines very often have premature bearing and gear failures, some of them related to the lubricants used. Five fully formulated wind turbine gear oils with the same viscosity grade and different formulations were selected and their physical characterization was performed. The lubricant tribological behaviour in a thrust ball bearing was analyzed. A modified Four-Ball Machine was used to assemble the bearings. They were submitted to an axial load and the tests were performed at velocities ranging between 150 and 1500 rpm. Experimental results for the operating temperatures and for the internal friction torque are presented.     

Ionic Liquids as Novel Lubricants and Additives for Diesel Engine Applications

The lubricating properties of two ionic liquids (ILs) with the same anion but different cations, one ammonium IL [C₈H₁₇]₃NH.Tf₂N and one imidazolium IL C₁₀mim.Tf₂N, were evaluated both in neat form and as oil additives. Experiments were conducted using a standardized reciprocating sliding test with a segment of a Cr-plated diesel engine piston ring against a gray cast iron flat specimen. The cast iron surface was prepared with simulated honing marks as on a typical internal combustion engine cylinder liner. The selected ILs were benchmarked against conventional hydrocarbon oils. Substantial friction and wear reductions, up to 55% and 34%, respectively, were achieved for the neat ILs compared to a fully formulated 15W40 engine oil. Adding 5 vol% ILs into mineral oil has demonstrated significant improvement in the lubricity. One blend even outperformed the 15W40 engine oil with 9% lower friction and 34% less wear. Lubrication regime modeling, worn surface morphology examination, and surface chemical analysis were conducted to help understand the lubricating mechanisms for ILs. Results suggest great potential for using ionic liquids as base lubricants or lubricant additives for diesel engine applications.     

Friction forces and plastic strain of plain bearings in airplanes

The paper presents data on the ultimate contact in tribojoints made from aviation antifriction structural materials and lubricants under friction and static loading. The significant influence of the friction force on the plastic strain of collars at heavy-duty contact is shown. For some combinations of structural and lubricating materials, friction decreases the ultimate pressure in the plain bearing by three times relative to static loading, under which collar plastic strain starts. The substitution of the lubricant augments (or decreases) the carrying ability by 2.5 times. The coefficients for calculating the equivalent stresses on the plain bearing friction surface are given in accordance with the results of comparative tests. The underestimation of friction forces may cause the breakdown of tribological components, as well as failures and crashes.     

基于正交试验的含氮硼酸酯铝材轧制润滑油摩擦学性能研究

合成一种新型含氮硼酸酯铝材轧制润滑油添加剂,利用四球试验机考察添加含氮硼酸酯的铝材轧制润滑油的油膜强度、摩擦因数,通过显微镜观察磨斑形貌并测量磨斑直径。利用正交试验法评估极压剂含量、基础油种类、四球试验机载荷和转速对含氮硼酸酯润滑油摩擦学性能的影响,并通过多目标优化设计,对4种参数对铝材轧制润滑油摩擦学性能的强化效果进行综合研究。结果表明:各工艺参数对油样的摩擦学性能影响显著性由大到小依次为极压剂添加量、基础油种类、转速和载荷;经过多目标优化设计,得到的含氮硼酸酯铝材轧制润滑油强化工艺参数的最佳组合:极压剂质量分数为1.0%,基础油种类为D100,载荷为294 N,转速为1 200 r/min;通过极差、方差等分析,发现极压剂添加量和基础油种类对油样的摩擦学性能有显著影响。     

Compatibility of DLC coatings with formulated oils

In the present study, the tribological performance and compatibility of hydrogenated amorphous carbon coating (a-C:H) and metal-doped diamond-like carbon (DLC) coating (Me-C:H) with formulated oils under the boundary lubrication regime was investigated. The investigation employed ball-on-flat contact geometry in reciprocating sliding motion and six formulated oils (manual gearbox oil, automatic gearbox oil, hydraulic oil, compressor oil, and normal and high performance motor oil), with pure poly-alpha-olefin (PAO) oil used as a reference. In addition, DLC coatings behavior in diesel and gasoline fuel was evaluated.Compared with the uncoated steel surfaces a-C:H coatings give improved wear resistance in base PAO as well as in fully formulated oils and fuels. On the other hand, W-doped DLC coatings show the lowest steady-state friction under boundary lubrication, especially when using oils with high additive contents.     

Tribological degradation of two vegetable‐based lubricants at elevated temperatures

Renewable‐based lubricants are being considered as potential alternatives to petroleum‐based lubricants for various reasons, mainly increased environmental sensitivity. However, understanding the tribological performance of such vegetable‐based lubricants under elevated temperatures is critical for their industrial implementation. This study focuses on the friction and abrasion rate characteristics of soybean and sunflower base oils in comparison to a base mineral oil under sliding wear at elevated temperatures. It was found that the abrasion rate and friction were less severe for the vegetable‐based lubricants up to temperatures around 100°C. The observed performance of the vegetable‐based lubricants was verified using a kinetic reaction mechanism model of lubricant degradation. Copyright © 2007 John Wiley & Sons, Ltd.     

水基边界润滑剂的摩擦特性

本文介绍了采用Ｍ－２００摩擦磨损试验机在所给定的各级负荷下,对所合成的用于水基边界润滑系统的边界润滑剂,进行的摩擦特性的试验,结果表明：在以水为溶剂的边界润滑系统中,负荷对摩擦特性的影响有效地反映该系统的润滑性能的优劣,与大挂等人所测定的温度对边界润滑剂的摩擦特性影响具有同样的效果。     

Lubricated wear behavior of leaded α+β brass

In this research investigation, the lubricated wear behavior of leaded α+β brass sliding against stainless steel counterface was studied with the aid of a pin-on-disk apparatus. The main objective of this work was to study the effect of aqueous based environments on the interface and tribological characteristics of this tribosystem, as in several cases the formation of a thin corrosion product layer can act as a lubricating film, decreasing the coefficient of friction of the tribosystem. Thus distilled water and 3.5% NaCl solutions were used as possible lubricants and were then compared with a commercial SAE 80 W lubricant, which is extensively used in many light and heavy-duty, automotive, commercial or industrial applications. From the experimental results obtained, Stribeck curves for each lubricative environment were exacted and analyzed. In addition, by evaluating changes in the coefficient of friction of the tribosystem in accordance with the observed wear mechanisms, the characteristic lubrication regimes (elastodynamic, mixed and boundary) were identified in these curves.     

Impacts of Friction-Modified Fully Formulated Engine Oils on Tribological Performance of Nitrided Piston Rings Sliding against Cast Iron Cylinder Bores

The tribochemical interaction in a nitrided piston ring/cast iron cylinder bore sliding contact with two commercial fully formulated engine oils (ILSAC GF-2 and GF-3 category, referred to as modified GF-2 and modified GF-3, respectively) supplemented with molybdenum dithiocarbamate (MoDTC) friction modifier was investigated in a laboratory bench test. Test results indicated that the modified GF-2 oil could produce a rapid friction reduction while the modified GF-3 oil maintained a stable and lower coefficient of friction (μ = 0.03) for a longer testing time. The modified GF-3 oil also generated a lower wear rate compared with the modified GF-2 oil under the same tribotest conditions. Based on SEM/EDX analyses of wear tracks on the tested tribo-components, it appears that the better formed tribofilm on both the lower and upper specimens by the modified GF-3 oil made a significant contribution to its tribological performance compared with the modified GF-2 oil when sliding under the same test conditions.     

Effect of lubricants on the friction and wear of Al2O3 against gray cast iron

The tribological behavior of ceramic Al₂O₃ coupled with gray cast iron (PHT) with different lubricants was investigated using a ring-on-block wear tester. In the wear test, air, distilled water, emulsion and oil were used as lubricants respectively in order to check the lubricating effectiveness of lubricants and the friction mechanism of solid graphite in the cast iron. Wear testing of 0.8% C steel (T8) sliding with Al₂O₃ was also carried out to compare with the test using gray cast iron. From these data the tribological behavior of graphite in the iron can be evaluated. The results show that the friction and wear of tested couples are decreased using different lubricants in the following order: air, distilled water, emulsion and oil. When lubricating with air and water, graphite in the iron as solid lubricant can decrease the friction and wear of the couples. However, when lubricating with emulsion and oil, graphite does not show the advantage of decreasing friction and wear.     

Performance evaluation for aged environmentally adapted lubricants in bronze‐steel sliding contacts

Environmentally adapted lubricants (EALs) are becoming of increasing interest to the industry as legislation demands the replacement of mineral oil lubricants. However, little or nothing is known about the influence of ageing on the performance of these fluids in mixed and boundary lubricated tribological contacts. In this study, samples of three fully formulated lubricating oils, both in their ‘unaged’ form and ‘aged’ by means of an oxidation process in the laboratory, were utilized in a detailed study whereby variations in relative lubrication performance were examined. Standard laboratory pin‐on‐disc equipment was utilized in order to allow comparisons to be made and the definition of conclusions for a sliding tin bronze on steel contact. This simulated the interaction between an oil‐lubricated bronze bushing and steel shaft as found in the vane adjustment mechanism of a Kaplan turbine. X‐ray photoelectron spectroscopy analysis was employed to assess the effect on surface layer structural chemistry. Results showed, for the specific application being investigated, that EALs continue to function well in terms of their friction and wear performance even at high acid numbers. Copyright © 2008 John Wiley & Sons, Ltd.