On the influence of surface finish of SSiC on the results of tribological laboratory tests in the case of water lubricated oscillating sliding

The development of materials for tribological applications requires characterisation of their friction and wear behaviour. This characterisation is often based on tribological model testing, working with simple shaped specimens, running under well-defined conditions. Discrepancies in test results may arise from the fact that non-standard tests with different sets of operational parameters are used. An essential starting point for the development of tribological standards is knowledge of the main parameters that influence the tribological properties. One aspect that is not often adequately taken into account is the surface finish of the test specimens. Results are presented of friction and wear tests with self-mated SSiC couples (ball on disc), running in water in an oscillating sliding mode. The surfaces of the disc were ground, lapped, or polished, respectively, running against a polished ball. For certain test conditions, the influence of the surface finish on wear is found to be negligible, while for other conditions, the wear rate can differ by one order of magnitude or even more. The consequences for the standardisation of wear tests of ceramic materials are discussed.     

面接触条件下织构表面摩擦特性研究

为研究织构表面对面接触摩擦副摩擦特性的影响,设计和制造4个表面高度算术平均值相同、表面微凹坑面积占有率分别为7%、14%、21%、28% 的试件,选用HDM20端面摩擦磨损试验机,针对油润滑和脂润滑两种润滑剂,在不同载荷、转速等工况和不同摩擦副配对材料等条件下进行了试验研究,探讨表面形貌对摩擦特性的影响规律,并使用Talysurf CCI Lite 非接触式三维光学轮廓仪对试样进行三维表面测量,采用ISO25178定义的体积参数和连通性系数对三维表面形貌进行表征,从而得出表面体积参数及连通性系数与摩擦因数的关系。结果表明：在油润滑条件下表面形貌的微观结构特性对摩擦的影响要比脂润滑条件下的更显著;在钢对铜摩擦副条件下织构表面的摩擦因数变化比较复杂,在钢对钢摩擦副条件下织构表面的摩擦因数变化相对平稳;在不同的条件下,最优的表面微观结构特性也不同;将连通性系数和体积参数结合起来对表面形貌进行表征将更有利于表面微观结构特性的摩擦学设计。     

Boundary lubrication mechanisms of carbon coatings by MoDTC and ZDDP additives

Fuel economy and reduction of harmful elements in lubricants are becoming important issues in the automotive industry. An approach to respond to these requirements is the potential use of low friction coatings in engine components exposed to boundary lubrication conditions. Diamond-like-carbon (DLC) coatings present a wide range of tribological behavior, including friction coefficients in ultra-high vacuum below 0.02. The engine oil environment which provides similar favourable air free conditions might lead to such low friction levels.In this work, the friction and wear properties of DLC coatings in boundary lubrication conditions have been investigated as a function of the hydrogen content in the carbon coating. Their interaction with ZDDP which is the exclusive antiwear agent in most automotive lubrication blends and friction-modifier additive MoDTC has been studied. Hydrogenated DLC coatings can be better lubricated in the presence of the friction-modifier additive MoDTC through the formation of MoS₂ solid lubricant material than can non-hydrogenated DLC. In contrast, the antiwear additive ZDDP does not significantly affect the wear behavior of DLC coatings. The good tribological performances of the DLC coatings suggest that they can contribute to reduce friction and wear in the engine, and so permit the significant decrease of additive concentration.     

Tribological studies of unpolished laser surface textures under starved lubrication conditions for use in air-conditioning and refrigeration compressors

An experimental study was carried out to investigate the tribological performance of different laser surface texture patterns, with unpolished material bulges around the dimples, under realistic operating conditions of starved lubrication, for use in air-conditioning and refrigeration compressors. Compared to untextured gray cast iron surfaces, the texture patterns showed significant tribological improvements. Long durability tests also highlighted the long term usefulness of surface texturing. The dominant wear mode of the texture patterns was found to be mechanical polishing and the tribological behavior was found to be largely independent of the type of lubricant or refrigerant.     

聚合物复合材料自润滑体系内外因素的摩擦学相互作用

从聚合物基复合材料在不同无润滑工况下的设计角度,讨论了高温、高压、高速、对偶、气体介质等外部因素对不同材料摩擦磨损性能的影响,分析了摩擦磨损机制,分析得出:由于填料、聚合物基体、对偶、工作介质之间存在着复杂的非线性相互作用,摩擦化学反应的程度与类型不同,不同填料填充聚合物基复合材料都有各自适用的摩擦系统,没有任何一种材料能适用于所有摩擦系统;指出目前摩擦学理论多建立在常温低压低速体系下,这与工程应用实际相脱节,对于复合材料在极端工况下的摩擦学机制、内外因素相互作用的研究,还有待进一步深入展开。     

The Effect of Different Temperatures on Friction and Wear Properties of CFRPEEK against AISI 431 Steel under Water Lubrication

The tribological behavior of 30 vol% carbon fiber–reinforced polyetheretherketone (CFRPEEK) against AISI 431 steel under different temperatures of water lubrication was investigated. Friction and wear tests were carried out on a disc-on-disc contact test apparatus under different operating conditions. The results reveal that the lubricant temperature has a significant effect on the friction and wear properties of CFRPEEK sliding against AISI 431 steel. The average friction coefficient and wear rate of CFRPEEK increase with increasing lubricant temperature. However, the wear rate of AISI 431 steel did not have a positive correlation with the wear rate of CFRPEEK under different temperatures of water lubrication. Moreover, the original and worn surfaces of CFRPEEK and AISI 431 steel were imaged by environmental scanning electron microscopy and optical microscopy, respectively. The main tribological mechanisms of CFRPEEK sliding against AISI 431 steel were adhesive wear, and increasing the temperature of the lubricant could accelerate wear.     

一种新型摩擦材料在水润滑下的摩擦学性能研究

采用环块式摩擦磨损实验研究了一种新型摩擦材料在水润滑状态下不同载荷与转速对试样摩擦学性能的影响,并对比干摩擦条件下的摩擦学性能变化,借助磨损表面形貌观察分析其磨损机理。实验结果表明:水润滑条件下,摩擦系数随着载荷的增大而减小,随着转速的提高先增加后减小;磨损率随着载荷与转速的提高都减小。相同载荷与转速下,干摩擦时磨损机理以磨粒磨损和黏着磨损为主,而水润滑条件下水形成边界润滑,磨损机理以磨粒磨损和轻微的黏着磨损为主;水润滑条件下摩擦系数和磨损率均低于干摩擦,主要是由于水起到了润滑和冷却的作用,阻止了转移膜的形成,并在材料表面形成水膜起到了边界润滑的作用。     

石墨含量对石墨固体润滑涂层摩擦学性能的影响

利用简便的刷涂法在钢基体表面制备了石墨固体润滑涂层。利用MM-200型摩擦磨损试验机对不同石墨含量的固体润滑涂层进行了详细的摩擦学性能对比试验。结果发现．石墨固体润滑涂层的摩擦学性能与石墨含量之间呈“马鞍形”变化规律，当石墨的质量分数为28％时，固体润滑涂层的减摩、耐磨性能最佳。     

磷硼氮型润滑添加剂的制备及摩擦学性能研究

以蓖麻油酸为载体,引入磷、硼、氮元素,合成出一种新型的润滑添加剂PBN,对其理化指标进行了测定,并用红外光谱对合成样品进行了表征,同时考察了样品的摩擦学性能.结果表明,样品具有较好的抗磨减摩性、油溶性、抗腐蚀性,是一种综合性能较好的润滑添加剂.     

Tribological behavior of PEEK-based materials under mixed and boundary lubrication conditions

In modern industries, more and more mechanical components are exposed to mixed and even boundary lubrication conditions, inducing fast wear and even scuffing of the motion systems. In order to enhance the lifetime and reliability of the motion systems, replacing metal–metal friction pairs by metal–polymer ones can be one of the most effective approaches. The present work focuses on tribological behavior of pure polyetheretherketone (PEEK) and a formulated PEEK composite lubricated with diesel and engine oil. It was demonstrated that in mixed and boundary lubrication regimes the structure of PEEK materials affect significantly the tribological performance. Formation of a tribofilm on the surface of metallic counterbody plays an important role on the tribological behavior of the PEEK-based materials.     

Ultralow friction of DLC in presence of glycerol mono-oleate (GNO)

This paper presents a unique tribological system that is able to produce no measurable wear of material combination and that reduces friction markedly in the ultralow regime under boundary lubrication. Ultralow friction (0.03) was obtained by sliding hydrogen-free Diamond-Like-Carbon ta-C against ta-C lubricated with Poly-alpha Olefin base oil containing Glycerol Mono-Oleate (GMO) additive. The origin of ultralow friction in these conditions has been investigated by surface analysis techniques. Results are in agreement with the formation of a OH-terminated carbon surface. This new surface chemistry might be formed by the tribochemical reaction of alcohol function groups with the friction-activated ta-C atoms. The origin of low friction could be due to the very low-energy interaction between OH-terminated surfaces.     

半金属基粉末摩擦片摩擦磨损性能研究

在不同工况下研究半金属基粉末摩擦片与淬火45#钢配副时,载荷和转速对其摩擦磨损性能的影响,并分析其磨损机制。结果表明,在油润滑和水润滑下,半金属基摩擦片高速下的磨损量要明显低于低速下的磨损量,而干摩擦下其高载高速下的磨损要高于高载低速时的磨损量。油润滑下随载荷的增大,半金属基摩擦片的摩擦因数逐渐升高;水润滑下随载荷的增大,高速时摩擦因数先增大后减小,低速时则逐渐降低;干摩擦下随载荷的增大,高速时摩擦因数呈现出先升高后降低再升高的趋势,低速时则先升高后降低。干摩擦时摩擦面十分粗糙,有比较明显的沟状磨痕和硬质颗粒脱落后残留的凹坑;而水润滑和油润滑时摩擦面较为光滑。     

Effect of chemical structure of borates on the tribological characteristics of magnesium alloy during sliding

Effects of four borates with different chemical structure on the tribological properties of magnesium alloy in sliding contact with bearing steel were investigated under boundary lubrication using a Timken type tester. It was shown that the borate without active element is not effective at reducing the friction and wear of magnesium alloy, and the borates containing nitrogen, sulfur and chlorine are effective at improving the tribological properties of magnesium alloy. Different active elements have different action characteristics at improving the tribological properties of magnesium alloy. The rubbed surfaces were investigated using Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS), the wear mechanisms were also proposed.     

水润滑条件下制动材料摩擦学性能研究进展

汽车刹车片摩擦因数在雨天或湿润的环境里衰退到非常低的水平是一个很严重的问题,直接威胁到交通安全。但目前国内外关于摩擦材料的试验规范并没有涉及到水润滑条件,相关的研究应越来越受到人们的重视。介绍摩擦材料在水润滑条件下的摩擦性能及相关研究的现状,对比干、湿2种条件下的摩擦机制,表明水作为一种冷却介质和润滑介质,对摩擦材料性能产生了复杂的影响。提出水润滑条件下摩擦材料的研究方向。     

水润滑下偶件表面粗糙度对PTFE复合材料摩擦学性能的影响

通过水润滑下的摩擦磨损实验,研究了偶件表面粗糙度对MoS2/PTFE复合材料摩擦学性能的影响,分析了在不同的偶件表面粗糙度下的摩擦学行为.实验结果表明:在水润滑下,一般存在着一个较佳的偶件表面粗糙度范围,在这个范围内可以取得较低的摩擦因数和磨损率;当偶件表面粗糙度高于这个范围时,摩擦磨损机制主要是机械作用;而当偶件表面粗糙度低于这个范围时,则主要是由于分子作用导致摩擦磨损.即当偶件表面粗糙度超出某一范围时,摩擦磨损行为将发生转变.     

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.     

TiAlN涂层往复滑动的摩擦学性能研究

为研究硬质合金表面沉积的TiA lN涂层的摩擦学行为,在不同介质(干态、乳化液、冷却油)条件和试验参数(法向载荷和位移幅值)下,进行了往复滑动摩擦磨损试验。在动力学分析基础上,结合光学显微镜(OM)、激光共焦扫描显微镜(LCSM)、扫描电子显微镜(SEM)和电子能谱(EDS)等微观分析手段对摩擦学性能进行了研究。结果显示:在同样条件下,涂层在试验初期的摩擦因数较小;法向载荷增大,涂层的摩擦因数降低,而位移幅值对涂层摩擦因数的影响不明显;基体的磨损机制主要为磨粒磨损,而涂层剥落是剥层和氧化磨损共同作用的结果;在润滑条件下,涂层的摩擦学性能得到了很大的改善,使涂层寿命得到显著延长,其中冷却油的效果最明显。     

多孔UHMWPE的制备与摩擦学性能研究

用热压成型法制备多孔超高分子量聚乙烯(UHMWPE)和普通UHMWPE试样,在改制的摩擦磨损试验机上考察2种试样在水润滑和牛血清润滑下的摩擦磨损性能。结果表明:普通UHMWPE均处于边界润滑区域;多孔UH-MWPE在较低载荷下因可以获得额外的润滑而形成混合润滑,摩擦因数和磨损量较低,其磨损机制为轻微的擦伤磨损;随着载荷的增加,多孔UHMWPE试样的磨损量明显上升并高于同等条件下普通UHMWPE,呈现较严重的切削磨损;多孔UHMWPE只适合应用于低载工况下。     

Film Forming Behavior of Greases Under Starved and Fully Flooded EHL Conditions

Improving knowledge on the film forming behavior of greases is essential to be able to develop efficient greases. This article examines how operating conditions (e.g., temperature, lubrication condition [fully flooded/starved]) and base oil viscosity influence the film forming properties of greases by comparing the behavior of two lithium-based greases and their respective base oils in rolling point contact. It is found that the onset and degree of starvation is controlled by speed (u) × viscosity (ν)/load (W) factor (uν/W) and temperature and that low uν/W values promote entrainment of thickener into contact. Thus, grease with low base oil viscosity shows significant thickener entrainment in the low speed region compared to the one with high base oil viscosity, which leads to the formation of thickener-rich viscous material during extended running with the low base oil viscosity grease. The results suggest that the shape of the film thickness versus speed curve is viscosity and uν/W range dependent. Furthermore, for the test conditions used in this study, grease-lubricated contacts appear to shift from the initial fully flooded condition to starved condition over a prolonged running of 2 h. The results from this study concur with those reported in the literature that fully flooded oil elastohydrodynamic lubrication (EHL) theory or film thickness cannot be directly applied or taken as a guideline in grease-lubricated contacts.     

Mechanical and tribological properties of a novel aluminum bronze material for drawing dies

A new aluminum bronze material with aluminum content over the solubility limit and several trace elements, Cu-14Al-X alloy (X is trace elements), has been developed for drawing dies. The mechanical properties such as hardness, tensile strength and impact toughness were evaluated experimentally. The friction and wear behavior of the material was investigated under boundary lubrication conditions. The experimental results demonstrated that the developed alloy possessed higher tensile strength and hardness, lower friction coefficient and wear rate, compared to currently used aluminum bronzes, therefore it is expected to replace conventional iron-based materials that are commonly used for drawing dies. With the excellent anti-friction property and high carrying capacity, the new material, Cu-14Al-X alloy, will be able to provide precision drawing dies.