Effect of sulphur-type extreme-pressure additives on wear in rolling-sliding contact

This paper looks at the wear of steel under lubricated rolling-sliding contact, with two paraffinic oils and a pure n-hexadecane. A two-disc apparatus was used, with a constant applied load, the surfaces being analyzed by X-ray photoelectron spectroscopy. The oils were tested with and without additives (dibenzyl disulphide and diphenyl disulphide), and the differences analyzed.     

Improvement of antioxidation and antiwear properties of polyalphaolefin oils

Polyalphaolefin-based lubricating oils were tested on a four-ball tester, and in a stability test, with antiwear and antioxidant additives of different types, along with other (petroleum and alkylbenzene) base oils and additives. Antioxidant additives for PAOs essentially influence their thermo-oxidation stability. It was found that binary inhibitors increased thermo-oxidation stability effectively. In the antiwear tests, the addition of additives to PAOs sharply decreased wear scar diameters. A significant difference was observed in the action of small concentrations of antiwear additives as between PAO, alkylbenzene and mineral oils. Explanations of this behaviour are put forward.     

Lubricating oil additives and the environment — an overview

In this paper are reported some practical considerations relating to lubricant additive manufacture, and to additivated lubricants' impact on the environment. Widely used engine oil additives are mainly dithiophosphates, overbased calcium sulphonates, succinimidic dispersants, and polymer VI improvers. Production of these additives creates a potential environmental problems due to the hazardous emissions such as H₂S and HCl and sludge obtained during purification. New processes are described which lead to the reduction of toxic and other harmful pollutants. Gear oil additives, although these may be used in lower amounts, also make for ecological problems. A high quantity of sulphur-containing waste water is produced during manufacture of sulphurised EP additives. Some possibilities for recovering sulphur from this waste water are presented. The reduction of the chlorine content in EP additives is another important task, and new processes to produce EP additives with low residual chlorine content are discussed. Metal working fluid additives comprise emulsifiers, corrosion inhibitors, antiwear and EP additives. Their fabrication usually produces toxic and harmful residual products. Additivated lubricants may promote ecological injury. Oil leakage from engines working in harbours, parks, and entertainment areas are dangerous and difficult to avoid. To counter this, biodegradable base stocks were developed, but there are few data concerning the biode-gradability of the additives used. Used oils are generally collected and recovered, but a significant quantity of used oil is directly burned. Burning of additivated used oils in incorrect equipment leads to dangerous emissions, such as sulphur oxides. Because sulphur-containing additives cannot be replaced in engine oils or gear oils, the main ecological measure is the reduction of the quantity of used oils burned.     

含超细颗粒固液二相流对PSZ陶瓷与钢摩擦磨损特性的影响

在往复式摩擦磨损试验机上研究了含超细颗粒固液二相流对部分稳定二氧化锆（ＰＳＺ）陶瓷与ＧＣｒ１５钢滑劝副的摩擦磨损性能的影响。选择９０＾＃机械油和ＱＣ３０汽机油为基础油,分别加入五种超细固体颗粒,配制出不同浓度的２０种油样,分别在１６０１７０和１００℃温度下进行试验。结果表明：超细固体颗粒添加剂的用量、试验温度和基础油都影响陶与钢滑动副的摩擦磨损性能。对超细颗粒添加剂的润滑机理进行了初步探讨。     

Friction and wear of tribofilms formed by zinc dialkyl dithiophosphate antiwear additive in low viscosity engine oils

Friction and wear characteristics of low viscosity SAE 5W-20 engine oils containing different amounts of phosphorus were studied using two different test devices. One was a laboratory high frequency reciprocating rig (HFRR) testing new and used oils at low and elevated temperatures. A direct acting mechanical bucket (DAMB) sliding valvetrain bench test apparatus was used to measure the friction and wear performances of fresh engine oils containing 0, 0.05 and 0.1 wt% phosphorus for a cam lobe rubbing against a tappet insert. The tester was coupled with a radioactive tracer machine (RTM). The results show that in the region of low phosphorus concentration, friction is inversely correlated to temperature. The friction coefficient slightly drops with increasing temperature and increases with increased phosphorus concentration at elevated temperatures. Significant wear is produced at phosphorus concentrations lower than 0.02 wt% at most temperatures. Friction and wear are reduced with the addition of supplemental antiwear additives. MoDTC reduces wear more effectively than ZnDTC in the presence of ZDDP.     

Sulphurised vegetable oils as EP additives for industrial gear oil formulations

Renewable sources can provide, besides fuel, a wide range of feed stocks for the organic chemicals industry. Utilisation of non-edible vegetable oils and speciality chemicals has, therefore, become relevant in recent times. Sulphurisation of three triglyceride oils (karanja, rapeseed, and castor oils) and liquid wax (jojoba) has been investigated in detail in order to examine the potential of sulphurised vegetable oils for use as extreme-pressure (EP) additives for developing formulations for industrial gear oils. The capacity of these oils with respect to the uptake of sulphur, the limitations of some of the sulphurised products for use as EP additives, and the problems in developing such formulations for industrial gear oils, are discussed.     

Application of friction-polymer-forming additives for the running-in of rubbing surfaces

The ability of friction-polymer-forming (FPF) additives (monomeric organic esters and organic alcohols) to help in the running-in of rubbing surfaces is discussed. It is shown by scanning electron microscopy (SEM) that these additives form films on running-in surfaces. By a combination of ferrography, SEM and X-ray microanalysis the polymeric nature of the wear products of such films has been indicated.When a mixture of these additives is used, a synergistic effect is established and this is explained.The results obtained from the bench cold running-in of internal combustion engines using mineral oils containing FPF additives are presented. It has been found that the use of FPF additives permits the hot running-in of cylinder-piston sets in certain diesel and carburettor engines to be abandoned. The duration of the cold running-in using oils with a package of FPF additives may be as short as 10–15 min.     

纳米粒子作润滑油添加剂的研究与展望

纳米粒子作润滑油添加剂表现出极好的摩擦学性能。本文综述了各种类型纳米闰子作润滑油添加剂的摩擦学性能和机理，总结了纳米粒子作润滑油添加剂的特点，并提出了需要进一步研究的方向。     

Effect of dissolved oxygen on lubricating performance of oils containing organic sulfides

To elucidate the role of dissolved oxygen in the synergistic lubrication mechanism of oils containing organic sulfides, four-ball tests were conducted under increasing-temperature or two-step constant-temperature conditions by using oils with different concentrations of dissolved oxygen. In increasing-temperature tests, high oxygen concentration with DPDS (diphenyl disulfide) and antioxidant additives exhibited superior load-carrying capacity to reactive DBDS (dibenzyl disulfide) with the same antioxidant additives. On the contrary, in two-step constant-temperature tests, the oils containing antioxidant additives alone with high concentration of oxygen showed better performance than oils containing DBDS or DPDS. These results are discussed from the viewpoint of optimum composition of surface films and cooperative action of additives and oxygen.     

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.     

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.     

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.

     

Lubricant components from vegetable oils of indian origin

A number of transesterified and alkarylated derivatives have been synthesised from available vegetable oils of Indian origin. The viscosity, viscosity index, freezing points, load-carrying characteristics, friction coefficient, and thermo-oxidative stability of these derivatives as compared to highly refined hydrorefined hydrocarbon oils have been studied. It has been found that several esters of fatty acids of these vegetable oils have a high natural viscosity index, low pour points, and high thermooxidative stability, and can meet the requirements as base fluid components for energy-efficient, eco-friendly, long-drain interval, multigrade oils. These oils have markedly lower viscosities at 40°C, higher load-carrying characteristics, and lower friction coefficients than the base fluids of currently marketed multigrade oils. A 50% blend with hydrorefined hydrocarbon oils could prove highly viable. The above results clearly establish the potential for utilising these esters, either alone, or in combination with mineral oils, for formulating cost-effective high-performance, energy-efficient, and environmentally friendly lubricants. Performance characteristics of these oils as engine oils, automotive gear oils, and 2 stroke oil with conventional additives and with alternative additives are under investigation in comparison to the most advanced hydrocarbon based multigrade oil formulations of long-drain interval.     

抗磨型油膜轴承油极压抗磨性能的研究

用油膜承载能力及四球机试验等方法极压抗磨性能，以硫磷型极压抗磨剂和油性剂等为主剂进行复配，对油品配方研究及解决极压抗磨性能打下了基础，。产品轻工业现场使用试验证明，极压抗磨性能完全能够满足设备的使用要求。     

Tribological performance of ionised vegetable oils as lubricity and fatty oiliness additives in lubricants and fuels

Lubricity and fatty oiliness additives, also known as friction modifiers in the tribological vocabulary, are steadily gaining acceptance from lubrication engineers and lubricant formulators. The present communication describes how such additives function in various tribosystems and which parameters control lubricity of finished formulations. Extensive experimental data are presented to demonstrate the outstanding tribological performance of bio‐based lubricity and fatty oiliness additives produced by Elektrionization^TM of vegetable feedstocks. Featuring a unique combination of viscosity and polarity, ionised vegetable oils form sufficiently thick and resilient protective layers by adsorption to rubbing surfaces. It is shown that, unlike extreme pressure additives, which act when a direct asperity–asperity contact occurs in the boundary lubrication regime, ionised vegetable oils function by postponing the onset of the boundary lubrication regime. Copyright © 2009 John Wiley & Sons, Ltd.     

The influence of lubricating fluid type on the properties of biodegradable greases

The lubricating ability of a grease depends on both the base oil and the thickener. As a result of their intrinsic properties and/or because of their com‐patibility with thickeners and specific additives, base fluids have different influences upon the properties of grease formulations. It is well known that mineral oils are the most widely used lubricant bases due to their inherent lubricity and lower cost, but recent environmental concern has led to consideration of the use of vegetable oils and readily biodegradable synthetic fluids as raw materials in lubricating grease formulations. As well as the base materials, the additives for biodegradable greases should also be biodegradable. This requirement limits the kind of products that may be used in environmentally friendly greases. This paper presents comparative data concerning the tribological and physico‐chemical properties of biodegradable greases formulated with certain vegetable oils, such as rape seed oil, castor oil, and soybean oil or their mixtures, and synthetic esters. The improvement of the load‐carrying properties of biodegradable greases and the antioxidative effect of some suitable additives have also been studied, and the results are presented here.     

Engine oil ageing under laboratory conditions

In recent years the role of laboratory methods in investigating the effectiveness of engine oil additives has dramatically increased, especially in predicting the performance of engine oils under field conditions. Some results of research under laboratory conditions on the ageing of engine oils with different performance levels are presented in this paper. The role of the action of antioxidant additives in engine oils for gasoline and diesel engines is described. The paper includes the results of experiments over time in laboratory testing of doped motor oils, use of IR spectroscopy, and reference oils. Single‐ and multi‐cylinder engine test results are also discussed. New, effective additive packages for different engine oils are considered.     

Synergistic effect of antiwear additives and antioxidants in vegetable oil

Certain vegetable oils have been recognised as promising candidates for environmentally friendly lubricants. Their lubricity can be optimised using antiwear additives. However, decomposition of the additives, accompanied by auto‐oxidation of the vegetable oils, has been found to occur. In other words, the antiwear additives may degrade in vegetable oils, and give less oxidative stability. In order to understand the mechanism, oxidation testing of a vegetable oil was performed by monitoring the peroxide value (POV). It was observed that POV increases as soon as oxidation starts. The value reached 1400–1500 ppm within 50 h of reaction time. Then it decreased to an equilibrium value of 400–500 ppm within 200 h. Antioxidants to prevent peroxide generation were examined. Phenolic antioxidants and zinc dialkyldithiocar‐bamate exhibited good results with regard to preventing peroxide generation, whereas aromatic amines gave poor results. A synergistic effect that prevents the decomposition of the antiwear additives was found.     

The unacceptable face of lubricating oil additives

In order to extend the range of application of mineral lubricating oils, lubricant technologists attempt to enhance inherent oil properties by incorporating small amounts of additives. While there is little doubt that they succeed in their primary objective, additives by their very nature tend to be more reactive than the oils in which they are incorporated and there is always the risk of unexpected side effects in their use. This paper gives examples from industrial machines where lubricating oil additives have been responsible for serious lubrication problems and concludes that additives should only be used in situations where they are essential: full consideration should be given to possible harmful side effects