Synthetics versus vegetable oils: Applications,options, and performance

Environmental concerns have brought forward vegetable oils as alternatives to more expensive synthetic lubricant base stocks, in moderate operating conditions. The contents of various acids, such as oleic and linoleum, can be changed by selective breeding to produce more desirable lubricating properties and less oxidation vulnerability. Different tests are needed for such lubricants, and the Baader test has been modified to show the ageing stability of rapeseed oil raffinate, TMP trioleate, dioctyl adipate, and HOSO. Such oils can also be modified with additive packages.     

Ionic liquids with ammonium cations as lubricants or additives

A new class of more effective lubricants could lead to huge energy savings. Limited recent literature has suggested potential for using room-temperature ionic liquids as lubricants, however, only a few out of millions (or more) of species possible have been evaluated. In this study, a series of new protic alkylammonium ionic liquids were synthesized by neutralization and metathesis reactions, and have demonstrated promising lubricating properties as neat lubricants or lubricant additives, particularly for use with difficult-to-lubricate metals like aluminum. More than a 30% friction reduction was observed with ammonium-based ionic liquids compared to conventional hydrocarbon oils in reciprocating sliding tests of 52100 bearing steel on aluminum alloy 6061-T6511. The inherent polarity of ionic liquids is believed to provide strong adsorption to contact surfaces and can form a boundary lubricating film leading to friction and wear reductions. Other advantages of ionic liquids include (1) negligible volatility, (2) high thermal stability, (3) non-flammability, and (4) better intrinsic properties that may eliminate the need for more complex and expensive additive packages. With very flexible molecular structures, this new class of lubricants, particularly ammonium-based ionic liquids, can be tailored to fit a variety of applications.     

Experimental investigation of porous bearings under different lubricant and lubricating conditions

The performance of porous bearing under different lubricants and lubricating conditions was experimentally investigated in this study. In order to carry out the experiments, a new test rig was designed to determine the tribological properties of based sintered bronze journal bearings that were manufactured by powder metallurgy (P/M) techniques. To determine the effects of lubricating conditions with and without oil supplement (OS) on the tribological characteristics of these bearings under static loading and periodic loadings, some experiments were carried out using different lubricants. In the tests, pure base oil (SAE 20W50), two fully formulated commercial engine oils (SAE20W50) and lubricating oils with commercial additive concentration ratio of3% were used. The worn surfaces of test bearings were examined using optical microscopy. Experimental results showed that the change in friction coefficient was more stable and in smaller magnitude under static loading than that of periodic loading. In addition, the friction coefficient and the wear rate conducted with base oil resulted in higher values than those of fully formulated oils with and without OS lubricating conditions. The experimental results obtained in this study indicated that the correct selection of lubricant and suitable running conditions were very important on the tribological characteristics of porous bearings.     

Surface and Tribological Characteristics of Tribofilms Formed in the Boundary Lubrication Regime with Application to Internal Combustion Engines

One of the biggest challenges in engine tribology is to formulate appropriate lubricants, which will increase fuel efficiency by reducing friction, yet still provide good wear resistance. The lubricant should also be formulated to limit particulate and gaseous exhaust emissions to the levels allowed by current regulations. In real lubricant formulations there can be 10–15 additives and the interactions between additives must be taken into account. The effects of eliminating the friction modifier and friction modifier plus anti-wear additive zinc dialkyl dithiophosphate (ZDDP) from the additive package of fully formulated lubricants on friction, wear and wear film forming characteristics have been examined. Tests have been conducted under lubricated wear conditions at bulk oil temperatures of 20, 50, and 100 °C using a reciprocating pin-on-plate tribometer. Boundary lubrication conditions were varied according to the value of starting lambda ratio. The wear film has been examined by Energy Dispersive X-ray analysis (EDX) and X-ray Photoelectron Spectroscopy (XPS). In order to investigate the morphology of the reaction films formed by the additive packages of these lubricants, Atomic Force Microscopy (AFM) was used. In this paper it has been shown that tribofilms, derived from ZDDP/surface interactions, affect friction, the extent of which is determined by tribological conditions. Detergent interactions with ZDDP enhance the complexity of the tribofilm and enrich the level of C in the film whilst affecting the friction and wear response. Through integration of tribological measurements and surface analysis, progress towards improving the nature of interactions is made and forms the focus of the paper.     

Effect of phyllanthus emblica biodiesel based lubricant on cylinder liner and piston ring

In the present time, need of biogenic lubricants is the focusing area which will be biodegradable, avirulent and eco-friendly. Current experimental tests depict the effect of ‘Phyllanthus emblica’ a non-edible feedstock through pin on disc tribo tester. Tests were conducted to evaluate the impact of 0, 10, 20 and 30 % blending of Phyllanthus emblica with SAE20W40 lubricating oil on cylinder liner and piston ring. Promising results have been manifested with 10 % blending of biodiesel (BD) with lubricating oil in terms of coefficient of friction and specific wear rate in comparison with other examined feedstock. For analysis of wear debris in the used oil analytical ferrography was also done. The effects of temperature on wear and friction characteristics have also been discussed.

     

Lubrication potential of boron compounds: An overview

Boron compounds are emerging as promising materials for a wide range of applications in automotive and industrial lubrication systems. Several studies conducted on boron compounds have revealed that they exhibit desirable properties for preparing stable and compatible lubricant components for a new generation of lubricating oil formulations. Boron‐containing lubricants have major tribological advantages, such as antiwear efficiency, good film strength, high‐temperature resistance, and self‐lubricating properties. The increasing number of patents concerning boron‐containing lubricants illustrates commercial interest in this area. Boron lubricants can be used in many forms, such as oxides, esters, and boric acid. Therefore, it can be expected that a new generation of lubricant formulations includes boron compounds. This paper presents an overview of various solid and liquid lubricants containing boron as an important ingredient, and is intended to aid the development of new lubricants.     

Some Improvements in Solid Lubricants Coatings For High Temperature Operations

In order to satisfy the growing request in solid lubrication for high temperatures, new solid lubricants are being developed. In this field the “quasi” solid lubricants and the soft nonabrasive film-forming lubricants constitute two important families.

In the family of “quasi” solid lubricants an evaluation of lead monoxide-lead silicate coatings has been performed, particularly through the examination of the effect of minor addition of metallic materials, such as aluminum, iron and stainless steel, on the lubricant properties of coatings. These coatings are obtained through the melting and partial devitrification of lubricants. The lubricating properties of the coatings have been evaluated at different temperatures, with different load, with the rider wear and friction test.

The system PbO-SiO₂-Fe has shown the best properties (f = 0.2 at 650 C), and it may be utilized as a lubricant coating at temperatures to 650 C.

In the family of soft nonabrasive film-forming lubricants, an evaluation of CaF₂-base systems has been performed. In this case micrographic examinations, rider wear, and friction determinations have been carried out for evaluating the lubricating properties of the coatings.

For applications that foresee temperatures over a wide range, the CaF₂-BaF₂-A g system is the most promising for lubricant coatings (f = 0.32 at 25 C₁ f = 0.18 at 700 C); it may be used up to 800 C. For the temperature range 400–800 C, CaF₂-BaF₂ 60–40 w/o system may be utilized for its low friction coefficient (at 600–700 C, f = 0.20). Some improvements in solid lubricants coatings for high temperature operations are discussed.     

Mathematical model for the thickening power of viscosity index improvers: Application to engine oil formulations

It is essential for a lubricating oil blender to be able to quantify the contribution that each component entering in a formulation makes to the viscosity of the finished product. In this context several studies have been devoted to the modelling of the thickening power of different types of polymers at both high (100 °C and 40°C) and low (−15°C) temperature in base oils of various origins and viscosities. To complement these earlier investigations, it is necessary to quantify the effect of the additive package on the viscosity of the formulation. For this purpose, the effect of several DI packages of different performance levels has been investigated in order to derive appropriate mathematical models representing the contribution of these packages to oil viscosity.     

Antiwear Action of Mineral Lubricants Modified by Conventional and Uncoventional Additives

The authors of this paper investigated the influence of esters of rapeseed oil fatty acids on the lubricating properties of mineral lubricants containing chosen AW/EP additives. Methyl esters, ethylene glycol esters, and glycerol esters as well as some commercial AW/EP packages based on zinc dialkyldithiophosphate, S–P organic compounds, and sulphurized esters of fatty acids were tested. The tribological tests were carried out with the use of a four-ball machine. Antiwear (AW) properties of tested compositions were determined using their limiting load of wear (G_oz(40)). It appears that the AW action of esters of rapeseed oil fatty acids depends on their structure. The best AW action is shown by compositions of mineral oil lubricants containing AW/EP additives and methyl esters of rapeseed oil fatty acids. The SEM/EDS analysis of the scar surface layer indicated that the presence of these esters in lubricants causes a change in the interaction between AW/EP additives and the metal surface. These observations were confirmed by the XPS surface analysis.     

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。     

Tribological properties of some water-based lubricants containing polyethylene glycol under boundary lubrication conditions

The metal-working industry is increasingly interested in synthetic metalworking fluids and coolants. The excellent lubricating properties of polyalkylene glycols have been recognised in areas such as gear lubricants, hydraulic fluids, and compressor lubricants. The main purpose of the present work was to investigate the friction and wear properties of several polyethylene glycols and their synergy with a common water-soluble EP additive, using four-ball and ball-on-plate tribometers.     

An opportunity for partial replacement of phosphates and dithiophosphates in EP packages with boron-containing additives

The influence of a boric additive on standard four-ball machine lubricating parameters of tricresylphosphate, zinc-dithiophosphate and sulphurized esters of fatty acids is studied. The consumption of active elements from the bulk oil of some of the samples is estimated by atomic emission spectrometry before and after a one hour wear test. This analysis can provide valuable information for additive and surface film studies. A considerable amount of tricresylphosphate or zinc dithiophosphate can be replaced by the boric additive in synergetic mixtures, without sacrificing lubricating properties. This opens up an opportunity for the formulation of additive packages with improved ecological compatibility.     

Synthetic lubricating greases for the food industry

The requirements of lubricating greases in the deep-freezing industries, that lubricants do not undergo degradation of their lubricating properties, and the need for non-aromatic and non-toxic/non-carcinogenic lubricants in food production, are discussed. Experimental data on the applicability of synthetic oils as bases for synthetic greases, are presented.     

Lubricating and physico-chemical properties of CI- 4 plus engine oil dispersed with surface modified multi-walled carbon nanotubes

This paper studies the effect of surface modification of multiwall carbon nanotubes (MWCNTs) prior to dispersion in engine oil to improve the tribological properties. The MWCNTs are stabilised in the lubricant with two different surfactants cetrimonium bromide (CTAB) and sorbitan monooleate (SPAN 80) and the effect of surfactants on the tribological properties has been studied. Pristine and surface modified MWCNTs in weight per cent range of 0·5% are dispersed in CI4 plus diesel engine oil. The foaming tendency and other physico-chemical properties of test lubricant have been studied to investigate the effect of nano materials and surfactants. The anti-wear and anti-friction properties are tested on a four ball wear tester and the comparison is made to assess the relative performance of pristine MWCNTs over surface modified MWCNTs. A strong influence of the surface modification technique is found on lubricating and physico-chemical properties. Both CTAB and SPAN 80 could keep the MWCNTs stable in the lubricant without compromising the foaming tendency of lubricant and other physico-chemical properties. The friction and wear characteristics of lubricants have improved with the dispersion of surface modified MWCNTs while there is no improvement in the properties of lubricant dispersed with pristine MWCNTs.     

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。     

Physical properties and testing of organosilicon esters for their applicability as synthetic lubricants

The constantly growing needs of the operational parameters of machines and engines, especially for aeronautical use, have brought about greater demands on lubricating oils. Various synthetic materials have been used since the Second World War,¹ in increasing quantity, as substitutes for mineral based oil: esters from organic alcohols and mono- or dicarboxyl acids are among the most widespread. Quite a different type of synthetic oil is organosilicon compounds, known as ‘silicones’. This paper reports experimental data for a group of silicon compounds examined in comparison with other materials normally used as bases for synthetic lubricants.     

Lubricating properties of rapeseed‐based oils

Three commercially available hydraulic/transmission lubricants based on rapeseed oil have been investigated for their lubricating properties. The coefficient of friction, scuffing‐load capacity, and pitting resistance were evaluated, and the results compared with a corresponding commercial mineral‐based oil. The results showed in general a substantially lower coefficient of friction and better pitting resistance for rapeseed‐based oils than for the mineral oil. Scuffing load capacity was, with one exception, the same for all oils. As a result of lower shear stresses during contact, and a higher viscosity index, the temperatures in the gearbox were lower for the rapeseed oils tested than for the mineral oil. Insufficient antiwear behaviour at high loads was found to be a major drawback of these vegetable oils.     

SYNTH—8添加剂抗磨损性能的研究

本文研究了ＳＹＮＴＨ－８添加剂的抗磨损性能，并对其作用机理作了分析。四球机实验表明：在４０＾＃润滑油中加入４％ＳＹＮＴＨ－８添加剂，其最大无卡咬值增加５４％；在自制磨损同上的试验和铁谱分析表明ＳＹＮＴＨ－８添加剂极大地提高了润滑油的承载能力，并且其铁谱片上存在大比例细小磨粒。     

磨损自补偿润滑添加剂 ZT2 的摩擦学特性试验

在基础油Ｌ－ＡＮ４６中测定了磨损自补偿添加剂及对比添加剂二烷基二硫代磷酸锌的各项摩擦学性质,研究证实添加剂ＺＴ２对钢／钢摩擦副具有磨损自补偿功能,产生了优异的综合摩擦学效应,摩擦副的减摩性、耐磨性和抗擦伤性均得到了显著的改善。     

Friction and Wear Behavior of CF/PTFE Composites Lubricated by Choline Chloride Ionic Liquids

The use of ionic liquids (ILs) as lubricants has received increasing attention in recent years. The use of ILs, however, is limited by the corrosion problem and their potential toxic property. Here we present the results of our initial study on the tribological properties of carbon fiber (CF)-filled polytetrafluoroethylene (PTFE) composites, which have an excellent chemical resistance property, lubricated by choline chloride ILs. The difference between choline chloride ILs and water and hydraulic oil as lubricants was studied at the same time, as was the effect of the anion on the lubricating property of choline chloride ILs. The worn surface and transfer film of CF/PTFE composites were studied by scanning electron microscopy. Our results indicate that the lubricating property of choline chloride ILs is much better than that of water and hydraulic oil. The friction coefficient and wear rate of CF/PTFE composites lubricated with ILs were approximately 60 and 50 % lower than those under the dry friction condition. Among the three kinds of ILs tested, the best tribological properties of the CF/PTFE composites were found for those sliding in the mixture of 1,2-propanediol and choline chloride. The worn surface and transfer film of CF/PTFE composites were also much smoother than those under the dry friction, water lubrication, and hydraulic oil lubrication conditions.