Functional properties of microstructured cylinder liner surfaces for internal combustion engines

Internal combustion engines are still of major importance as propulsion systems. To fulfil future market and legislative demands it is necessary to improve engine performance, reduce fuel consumption, and limit exhaust emissions. Mechanical and thermodynamic losses, wear, and the emissions caused by lubricating oil combustion are principally influenced by the tribological behaviour of the piston assembly. The trend towards compact engines with high power densities and increased thermomechanical loads increases the importance of this tribological system and requires new approaches. One promising possibility is the utilisation of liner surfaces with specially machined microstructures. This paper describes a comparison between a conventional liner surface and a laser‐structured liner as regards their tribological behaviour. Measurements of wear as well as of oil film thickness and friction force in operation have been carried out. The results show better tribological behaviour for the laser‐structured liner surface than for the conventional plateau‐honed surface. This leads to lower fuel consumption and less wear.     

The study of tribological properties of laser‐textured surface of 2024 aluminium alloy under boundary lubrication

The tribological property of aluminium alloy is critical for its reliable operation in practical applications. In this paper, the tribological performance of laser‐textured 2024 aluminium alloy is studied in unidirectional sliding tests under boundary lubrication. The dimples were produced on the aluminium alloy surface by using a pulse Nd : YAG laser. The topographical microstructures of these laser‐induced textures were characterised by optical and scanning electron microscopy. In comparison with untextured surfaces, a significant improvement in friction behaviour was observed for the textured surfaces. The influences of dimples density on the tribological properties were investigated. Two types of oil with different viscosities were evaluated as lubricants. It was found that the beneficial effects of laser surface texturing are more pronounced at higher speed and load with higher viscosity oil. The optimum dimples density of 8.5% was found to have a lower friction coefficient. On basis of the experimental results, the mechanism of friction reduction and anti‐wear is proposed. Copyright © 2012 John Wiley & Sons, Ltd.     

修饰ZnS纳米粒子的减摩抗磨性能研究

利用SRV摩擦磨损试验机考察了粒径约为4nm的二烷基二硫代磷酸（DDP）修饰ZnS纳米粒子作为润滑油添加剂的磨擦学性能，并采用XPS对其摩擦表面进行了研究。结果表明：添加修饰ZnS纳米粒子在摩擦过程中会发生摩擦化学反应，形成一层边界润滑膜，该膜可有效提高十四烷的减摩抗磨和承载能力。     

双羟基硬脂酸在蓖麻油中的润滑性能的研究

利用四球摩擦磨损试验机考察了所合成的双羟基硬脂酸在蓖麻油中的摩擦学性能．并用扫描电子显微镜观察分析了磨斑表面的形貌。结果表明：双羟基硬脂酸添加剂可以显著改善蓖麻油的抗磨减摩性能和极压性能;含上述添加剂的蓖麻油在摩擦过程中发生了化学吸附反应,在摩擦表面形成了含双羟基硬脂酸的吸附膜．从而改善了蓖麻油的摩擦学性能。     

Combination of DLC coatings and EP additives for improved tribological behaviour of boundary lubricated surfaces

The aim of the present investigation was to obtain some further understanding of the mechanism responsible for low-friction behaviour of W-containing DLC coatings (W-DLC) when lubricated with EP additivated oil. Boundary lubricated wear and friction tests were performed under reciprocating sliding motion using a high frequency test rig and a contact pressure of 1.5 GPa. Additionally, some of the tests were performed in a load-scanning reciprocating test rig, with the contact pressure being in the range from 2.4 to 5.6 GPa. The influence of concentration of a sulphur-based EP additive on the friction behaviour was investigated.This investigation showed that W-DLC coatings greatly improve the tribological properties of boundary-lubricated surfaces, especially when pairing coated and uncoated steel surfaces. The improved tribological behaviour was found to be governed by the gradual formation of a WS₂ type tribofilm on the steel counter-face or on revealed steel substrate. The friction level depends on the additive concentration.     

Effects of Using Alternative Extreme Pressure (EP) and Anti-Wear (AW) Additives with Oxy-Nitrided Samples

Oxy-nitriding is a widely used industrial process aiming to improve the tribological properties and performance of components. Previous studies have shown the effectiveness of the treatment with friction and wear performance, but very few have focussed on optimising this behaviour. The lubrication properties of several EP and AW additives were examined to investigate their effectiveness in improving the tribological properties of the layers formed after treatment. Previous studies showed the presence of an oxide layer on the sample could improve the effectiveness of the sulphurised olefin (SO) and tricresyl phosphate (TCP) additives. The friction and wear behaviour of oxy-nitrided samples were analysed using a tribometer and surface profiler. Scanning electron microscope, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were employed to identify the morphologies and chemical compositions of the treated surface before and after testing. No real effect on friction was observed when using the SO or TCP additives, mostly due to lack of interaction with the less reactive iron nitride layer and their roles as anti-wear additives. However, when the zinc dialkyldithiophosphate-containing lubricant was used, a higher friction coefficient was observed. Greater improvements in anti-wear properties with the presence of additives in comparison with only using base oil were reported, with the TCP additive producing the lowest wear rates. The study effectively demonstrated that the additive package type used could impact the tribological and tribochemical properties of oxy-nitrided surfaces.     

A study of the tribological behaviour of dialkyldithiophosphate esters as additives in rape seed oil

Zinc dialkyldithiophosphates (ZDDP) cannot be used as additives in biodegradable lubricants because of their zinc content. In investigating substitutes for ZDDP, dialkyldithiophosphate esters have been synthesised, and their tribological behaviour as additives in rape seed oil has been evaluated using a four‐ball friction and wear tester and compared with that of ZDDP. The results show that these additives have better antiwear properties and load‐carrying capacity than rape seed oil alone. The morphologies and the elemental chemical states on the worn surfaces of the lubricated steel balls of the tester were examined using X‐ray photoelectron spectroscopy and scanning electron microscopy. The tribological mechanism is discussed on the basis of the experimental results.     

Surfactant dithiophosphates lubricating oil additives

Abstract

This paper presents a research on the tribological properties and the action mechanisms of surfactant lubricating oil additives, polyalkoxy glycol ammonium salts and O,O,S-triesters of polyalkoxy glycol dithiophosphoric acid. To understand the physicochemical properties of surfactants, polyalkoxy glycol dithiophosphoric acid behaviour both in solution and at metal surfaces are identified and discussed. The STM adsorption on steel surface, four-ball and ball disc tests of friction of water, synthetic and mineral oil solutions studies of these additives are presented. Friction and wear properties are dependent on tribological parameters, chemical structure of the additives and their surface active behaviour in tribological systems. The relationships are presented on the example of additives with different molecular structures and masses.     

富勒烯与纳米二硫化钨极压抗磨协同性能研究

为探讨富勒烯与纳米二硫化钨的极压抗磨协同性能,利用四球试验机考察富勒烯与纳米二硫化钨复配后在PAO基础油中的摩擦学性能;采用扫描电子显微镜对试验钢球磨痕形貌进行分析,探究富勒烯与纳米二硫化钨的协同作用机制。结果表明:富勒烯与纳米二硫化钨单剂对PAO基础油减摩抗磨效果的改善不明显,而富勒烯与纳米二硫化钨复配后可明显提高油样的减摩抗磨性能,其中质量分数0.01%富勒烯与0.005%二硫化钨复配后减摩抗磨协同效果最优,这是因为富勒烯能够实现滚动摩擦,而纳米二硫化钨能够沉淀到磨损处,起到修复的作用,两者的协同作用,提高了基础油的抗磨减摩性能;富勒烯与纳米二硫化钨复配并不能提高基础油极压性能,这是因为富勒烯不能与纳米二硫化钨生成新的物质来提高基础油的承载能力。     

Assessment of lubricity of compositions of fuel oil with biocomponents derived from rape-seed

This paper presents an assessment of tribological properties of compositions of fuel oil containing fatty acid methyl esters derived from rape-seed oil. An HFRR (high-frequency reciprocating rig – ball-on-flat) apparatus was used in this investigation. The studies were carried out for a steel–steel pair in the concentrated contact.The tribological properties were determined by motion resistances, wear and lubricant film concentration. The surfaces were analysed after tribological tests. The aim of the investigation was an attempt to obtain a correlation between wear quantities being measured and percentage content of bioadditives in fuel oil. It was found that at as little as 5% of the additive the coefficient of friction decreases by about 20% while wear decreases twofold relative to fuel oil, which may result from an increase in the stability of the lubricant film.     

Tribological performance of a DLC coating in combination with water-based lubricants

The tribological behaviour in water-based environments has been studied for a tungsten carbide-doped DLC coating (WC/C) deposited by physical vapour deposition (PVD) on bearing steel. Several tribological test equipments have been used to characterise the wear rate, coefficient of friction and resistance to seizure of the coated system, in comparison with uncoated bearing steel surfaces. It was observed that the wear was decreased and the coefficient of friction reduced in pin-on-disc measurements for poor lubricants. Further, the resistance to seizure in the four-ball method was improved by a factor of approximately three. Results from Reichert measurements showed a decreased wear rate and also a very pronounced running-in behaviour of the coating for some water-based lubricants. It has been shown that the performance of tribological systems with water-based lubricants can be significantly improved with this type of DLC coating.     

Comprehensive tribological characterization of thin TiN-based coatings

Innumerable papers have been published so far describing tribological investigations of thin hard coatings based on TiN. Analysis of the presented results demonstrates a large dispersion of measured friction and wear numbers, whereas TiN-coated pieces and tools have proved their benefits in a broad area of application. Therefore an attempt was made to clarify the influences on friction and wear test results by varying the coating process, the tribological stresses due to sliding, fretting and rolling motion and by changing the surrounding medium. The results reveal that machining of substrate surfaces and type of tribological stresses due to sliding, fretting and rolling have an important influence. The formation of reaction layers is dominating the tribological behaviour in most cases.     

点/线/面接触条件下喹唑啉酮胺润滑油添加剂的摩擦学性能

目前杂环化合物作为润滑油添加剂在机械润滑领域受到重视,但对无硫磷含氮杂环化合物在多种接触方式下的摩擦学性能的研究还不多。合成一种新型无硫磷喹唑啉酮胺润滑油添加剂并利用四球试验机、环块试验机和万能摩擦磨损试验机分别考察了点/线/面接触条件下其在液体石蜡中的摩擦学性能,再用光学显微镜、扫描电子显微镜和X射线光电子能谱仪对其摩擦表面进行分析。试验结果表明:油溶性喹唑啉酮胺在液体石蜡中能显著改善基础油的摩擦磨损状况,明显提高基础油的承载能力,表现出良好的摩擦学性能,其作用机理是其在摩擦过程中与金属表面发生了摩擦化学反应,生成了含氧化亚铁、有机氮化物和含氮金属配合物等的复合膜,有效地提高了液体石蜡的减摩抗磨性能。     

Bio-Fuel-Contaminated Lubricant and Hardening Effects on the Friction and Wear of AISI 1045 Steel

A study has been made on the wear and friction of hardened AISI 1045 steel using a tri-pin-on-disc type of friction and wear apparatus. During the investigation the linear pin wear, coefficient of friction and rise in pin specimen temperature were monitored and wear and friction curves plotted. Wear surfaces and mechanisms were investigated by means of optical microscopy. Analysis of used lubricating oil was performed using FTIR spectroscopy.

It was shown that the wear rate, type of wear and friction coefficient were influenced by contaminating the lubricant with bio-fuel as well as the surface hardening treatment. Corrosive wear and pits on the specimen surface were found when plain bio-fuel was used as lubricating oil. The results also confirmed that better wear resistance was obtained from the surface-hardened steel specimen with 4 % bio-fuel-contaminated lubricant.

Results from this study will be useful in material selection for tribological components in diesel engines running on vegetable fuel.     

Tribological behaviour of alumina sliding on several kinds of materials

Friction and wear behaviour of alumina sliding on various materials (nickel, copper, titanium, aluminium, alumina) were investigated experimentally. Pin-on-disc tests were conducted in air at various relative humidity levels (RHL). The results show that the influence of humidity depends on the material of the couples. Tribological behaviour of alumina sliding on very reactive metals such as titanium and aluminium is not influenced by RHL. In contrast, the friction coefficient and wear mechanism of nickel and copper are strongly affected by adsorbed films of water vapour. Nickel implanted with boron was also studied. The friction and wear of implanted surfaces are drastically reduced due to a lowering of the nickel surface reactivity. The tribological behaviour of the Al₂O₃/Al₂O₃ couple is also sensitive to RHL. The variation of friction coefficient and wear of this system are discussed in terms of tribochemical reactions and crack propagation.     

基于油液分析的汽车发动机摩擦系统故障诊断专家系统知识库的建立

采集汽车发动机润滑系统中摩擦副经历磨擦学行为的信息是诊断发动机摩擦系统故障的有效手段。油液分析从摩擦学系统的润滑剂和磨损物两方面获得磨擦副的润滑和磨损状态的信息。但常规的油液分析信息处理方法上的不足影响了油液分析技术在汽车行业的实际应用,开发基于油液分析的故障诊断系统,无疑会改善油液分析的诊断准确性和诊断成本。本文着重针对该诊断专家系统知识库的建立,     

二维层状Ni/β-Ni(OH)2纳米复合材料的制备及其摩擦学性能研究

采用水热反应制备出β-Ni(OH)2,然后通过水热还原得到Ni/β-Ni(OH)2纳米复合粉体材料,采用X射线衍射仪(XRD)和扫描电子显微镜(SEM)对复合材料的相结构、成分及形貌进行表征分析。采用四球摩擦磨损试验机评价制备的Ni/β-Ni(OH)2作为润滑油添加剂的摩擦学性能,基础油为PAO6。摩擦试验后,采用SEM分析典型试验钢球磨斑的表面形貌,利用能谱仪(EDS)研究磨斑表面化学元素的组成,探讨Ni/β-Ni(OH)2纳米复合润滑添加剂的减摩抗磨机制。结果表明:Ni/β-Ni(OH)2纳米复合材料作为润滑添加剂具有极好的减摩抗磨性能,显著优于基础油PAO6和未负载纳米Ni的二维β-Ni(OH)2层状材料;与基础油相比,添加0.1%质量分数Ni/β-Ni(OH)2添加剂的油样的摩擦因数和磨斑直径分别降低了17.6%和41.5%;Ni/β-Ni(OH)2纳米复合粉体综合了纳米Ni及层状β-Ni(OH)2两部分结构特性,在摩擦过程中,复合材料中的纳米金属粒子Ni与层状结构材料β-Ni(OH)2能够相互增强起到协同润滑作用。     

Exploration on tribological behaviours of perrhenates as potential lubricating oil additive during a wide temperature range

The perrhenates of calcium, copper and lead used as oil additive were synthesised by using the aqueous solution method. The tribological properties of these perrhenates were examined by using a ball‐on‐disc tribotester during a wide temperature range and a four‐ball testing machine at room temperature. The four‐ball test results showed that all synthesised perrhenates presented good extreme pressure property to a certain degree and demonstrated satisfactory wear resistance at room temperature. The ball‐on‐disc experiment results showed that the base oil with perrhenate additives significantly decreased friction and wear compared with pure base oil at elevated temperatures. An antifriction and low‐shear layer was verified to form on sample surface after testing under high temperature. This layer effectively prevented the direct contact of sliding surfaces and decreased the friction coefficient. The antifriction behaviour of perrhenates implied that they could be developed as the candidate of oil additives for a hybrid lubricating mode. Copyright © 2015 John Wiley & Sons, Ltd.     

The influence of oxygen on the friction and wear behaviour of a copper—steel couple under electric current

The tribological behaviour of a copper—steel couple similar to those in electrified railways has been studied as a function of mechanical, electrical, and environmental parameters. The experimental results obtained in an oxygen atmosphere show that this factor has a major influence on the wear behaviour. While there was a reduction in the average coefficient of friction compared to in argon, under oxygen there was twice the wear found under air, and six times that found under argon. In the absence of an electric current, the nature of the wear was essentially mild adhesive. However, with an electric current at the interface, fluctuations, particularly at high intensities, were recorded in both the coefficient of friction and the electrical contact resistance, and there was severe wear. Discussion of the results is based on examination of the wear surfaces and analysis of the phenomena observed during sliding contact.     

二烷基二硫代甲酸钼(MoDTC)摩擦改进剂对GF-3等级全配方发动机油摩擦学性能的影响

利用SRV高温摩擦磨损试验机研究了二烷基二硫代甲酸钼(MoDTC)对渗氮活塞环／铸铁缸套在ILSACGF-3发动机油润滑条件下的摩擦学性能的影响。结果表明，MoDTC能与GF-3全配方发动机油中的ZDTP／磺酸钙添加剂体系产生协同作用，在活塞环和缸套表面生成减摩和抗磨的摩擦反应膜，从而显著降低并在较长时间内保持低摩擦系数(最低0．03)，同时缸套的磨损降低50％以上。