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。     

Calcium sulphonate and its interactions with ZDDP on both aluminium-silicon and model silicon surfaces

The boundary lubrication of an aluminium-silicon cylinder liner operating under mild wear conditions has been investigated. The interface was lubricated with synthetic six centistokes poly alpha olefin base oil, which contained either calcium sulphonate or calcium sulphonate and zinc dialkyldithiophosphate. Effective replication of silicon grains within an aluminium-silicon alloy using a silicon crystal substrate affords valuable reproduction of tribofilms. The physical and chemical characteristics of films generated on either substrate were comparable. A marked difference in structure was exhibited between the tribofilms formed from either lubricant. Detailed tribological and tribochemical analysis has been conducted on either substrate.     

The Friction and Wear Model of Steels and Their Probable Statistic Calculations

Based on a systematic analysis of steel wear surfaces by Scanning Electron Microscopy (SEM) and Auger Electron Microscopy (AES), a statistical model for friction and wear of steels is proposed. Three categories of contact are proposed; oxide-oxide, metal-metal, and metal-oxide. Each category of contact is related to a probability distribution on the real contact area. Using a new concept of nascently exposed metallic surfaces, this paper derived the mathematical expressions for the friction coefficient and wear rate by means of statistical methods. The calculated values are in good agreement with measured values.     

Tribological investigation of layered sodium silicate as lubricant additives prepared by freezing titration ion exchange

Two layered sodium silicate products were prepared using a new ion exchange method called the freezing titration ion exchange. The tribological properties of the ion exchange products as additives in mineral oil were evaluated using a four-ball tester. The products exhibited excellent friction behavior when used as additives in mineral oil. When 1 wt% was added, the tribological properties of the oils improved: the maximum non-seizure loads increased by over 27% and the wear scar diameter and friction coefficient decreased by over 50% and 25%, respectively. The friction and wear behaviors of the silicates were better than those of the typical lubricant additives.     

Friction reducing effect of multiply adsorptive organic polymer

The relationships among molecular structures of multiply adsorptive organic polymers, their friction reducing effects and the properties of boundary films formed on surfaces were investigated using polymethacrylates (PMAs) as model additives in order to set guidelines for designing new effective additives for reducing friction. It was found that PMAs can reduce friction by forming adsorbed boundary films that retain structures similar to that of PMA additives on rubbed surfaces. The friction reducing effects of PMAs became larger with increasing molecular weight and increasing adsorptive polar groups. It is speculated that the enhanced friction reducing effects were caused by increasing the coverage of the boundary films formed on the surfaces and by decreasing solid contact between opposing surfaces.     

固体润滑涂层在干摩擦及有油条件下的摩擦磨损性能

采用MRH-3环块磨损试验机对FM-510二硫化钼润滑涂层在于摩擦及有油条件下进行了摩擦磨损性能的考察和评价,评价结果表明：该涂层在干摩擦条件下具有低的摩擦系数、高的承载能力和长的耐磨寿命,摩擦系数随负荷增高而降低,随速度提高也降低。摩擦偶对双面涂膜比单面涂膜有更长的耐磨寿命,速度低时涂层的磨耗小,寿命长,可满足特定条件下的干摩擦工作要求,在有油润滑条件下二硫化钼基的FM-510润滑涂层可显减轻对偶磨损程度,摩擦系数比单独使用油润滑时大大降低。在难以形成连续的流体润滑薄膜,亦即不能形成流体动力润滑的情况下。摩擦偶对涂敷固体润滑涂层是解决其润滑问题的有效方案。     

Friction and adhesion in boundary lubrication measured by microtribometers

The measuring and modelling of friction are critically important for the motion control in nanopositioning, particularly when bearings are employed to cover the wide working distances. Since the positioning system usually operates at very low speed to achieve fine positioning, the boundary lubrication is the dominant regime. A detailed characterization of the friction of boundary lubrication formed by Poly–α–Olefin (PAO) with and without surfactant and a suspension of MoS₂ in base oil has been performed in reciprocating sliding tests by steel/steel point contacts, and correlated with adhesion measurements by silicon/silicon point contacts. A microtribometer based on laser interferometers and glass springs, which can resolve 100 nN force in a speed range of 1–1000 μm/s was employed to detect the minute changes in forces. We find that a simple linear function instead of a logarithmic function is possible to describe the relationship between the friction force and operating speed for all the lubricants tested, though the gradients are quite different and under the influence of normal load. Comparing to PAO+surfactant and MoS₂ suspension, PAO shows a much higher load-dependent coefficient of friction. This result is further confirmed by the repulsion force measurements, which shows a higher increase of contact pressure with the increase of normal load for PAO.     

The Structural and Tribological Properties of MoS2-Ti Composite Solid Lubricants

MoS ₂ -Ti composite solid lubricant films were deposited on an AISI D2 tool steel and silicon wafer by CFUBMS (closed field unbalanced magnetron sputtering). The deposition process was performed for nine different test conditions at various levels of target current, working pressure, and substrate voltage using the Taguchi L ₉ (3 ⁴ ) experimental method. It was observed that the chemical composition of MoS ₂ -Ti composite films was significantly affected by sputtering parameters. It was determined that the microstructure of composite films is neither crystalline nor amorphous; in other words, it is quasi-amorphous, and (002) and (100) planes characteristic of MoS ₂ occurred. The friction coefficients of the films were determined over 1800 s and at a loading of 10 N by means of a pin-on-disk tribotester. The changes in friction coefficient were related to structural changes based on Ti addition and the different levels of deposition parameters.     

On the effort to discriminate the principal function of tribofilm on friction under the boundary lubrication condition

Friction coefficient under boundary lubrication conditions is affected by many factors. In order to study the friction characteristic of tribofilm, friction coefficient of tribofilm formed on steel disk under the boundary lubrication conditions was separately measured under dry condition using a laboratory-made micro-tribometer to eliminate the hydrodynamic lubrication action of fluid. This paper introduces the approaching method to understand the friction characteristic of tribofilm. In this paper, sliding speed dependency of friction exerted by tribofilm was observed that could not be interpreted by the classical boundary lubrication mechanisms. The additives having long alkyl chain showed strong sliding speed dependency of friction.     

冷轧塑性加工中的摩擦性质

根据轧制时轧件金属发生塑性变形特点及摩擦副间的介质实际情况,经理论分析认为冷轧塑性加工中的摩擦性质是混合摩擦或边界摩擦,并得到了实验的验证。     

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.     

Boundary film formation from overbased calcium sulfonate additives during running-in process of steel–DLC contact

The initial stage of boundary film formation from overbased calcium sulfonate at steel–DLC (diamond like carbon) contact was studied. A running-in process was clearly observed by the combination of fresh DLC with fresh steel or fresh DLC with rubbed steel. On the other hand, rubbed DLC does not possess the running-in process. Surface analysis by TOF-SIMS was applied to investigate the formation process and structure of films. It was found that the transfer of iron from the steel ball on to the DLC surface plays a significant role in the formation of boundary film. The depth profile of the film was also obtained by means of an etching technique. The boundary film on steel ball and DLC are mainly composed of iron and calcium oxide. However the depth profiles indicate that distribution of calcium oxide on steel ball is different from that on DLC coated disk.     

Comparison of the Effects of Biodiesel and Mineral Diesel Fuel Dilution on Aged Engine Oil Properties

Dilution of engine oil occurs when fuel is injected late in the combustion cycle to regenerate the diesel particulate filter used for trapping particulate emissions. Fuel dilution reduces oil viscosity and the concentration of engine oil additives, potentially compromising lubricant performance. Biodiesel usage may compound these issues due to its oxidative instability, and its higher boiling point compared to mineral diesel potentially causes it to concentrate more in the oil sump.

In this work, different amounts of mineral diesel and biodiesel (soy methyl ester, SME) were combined with 15W-40 CJ-4 diesel engine oil in laboratory oil aging experiments. Fuel was added and oil samples were withdrawn at periodic intervals. The oils were analyzed using typical oil analysis procedures to determine their condition, and wear evaluations under boundary lubricating conditions were determined using a high-frequency reciprocating rig (HFRR). Results showed that fuel dilution accelerated engine oil degradation, with biodiesel having a larger effect. However, friction remained unchanged with dilution, and wear actually decreased for fuel-diluted oils after 48 h of aging compared to aging without fuel dilution. Examination of the tribofilms by ultraviolet (UV) and visible Raman spectroscopy as well as Auger electron spectroscopy showed that additional carbon-containing components were present on tribofilms formed from fuel-diluted oils. These fuel-derived components may be responsible for the decreased wear observed.     

外加电压对边界润滑下钢/铜摩擦副摩擦磨损的影响

利用球盘式摩擦试验机,针对150SN油润滑下的GCr15/ZCu10Fe3摩擦副,研究了不同极性的外加直流电压对其摩擦系数和磨损状态的影响,并结合磨痕的能谱分析,探讨了外加电压对其摩擦磨损性能的作用机理。     

The Friction Reducing Properties of Molybdenum Dialkyldithiocarbamate Additives: Part II - Durability of Friction Reducing Capability

Material characterization and wear evaluation of the original and replacement pistons and cylinder liners from a Tiger 131 are reported. The original piston and cylinder liner were operative in the Tiger engine during WWII. The replacement piston and cylinder liner were used as substitutes and were obtained after failure in 2 h of operation in the actual engine. Material characterization revealed that the original piston was aluminum silicon hypereutectic alloy approximately matching the specification of RSA-419 AE, with a silicon content of 19.92 wt%. The replacement piston was aluminum copper alloy with a low silicon content of 0.73 wt%, approximately satisfying specifications of Al 2031 and Al 2618-T6. Scuffing, material removal, and ploughing were observed in the replacement piston and cylinder liner. These failures were attributed to inadequate piston material and design. The replacement piston average surface roughness was 9.09 μm and for the replacement cylinder liner it was 5.78 μm. Characterization results showed that both the original and replacement cylinder liners consisted of mostly iron, which is indicative of cast iron, a common material for this application.     

Improved anti-shudder performance of ATFs—Influence of a new friction modifier and surface chemistry

Among OEM strategies for increasing fuel economy and reducing emissions, driveline performance optimisation by using automatic transmissions is particularly important. Technology advances in automatic transmission designs are leading to continued growth of the number of vehicles with automatic transmissions. In fact, over the next five years, it is expected that the market share for automatic transmissions will increase to greater than 60%, with Europe being the largest region for this growth.The performance of automatic transmissions, especially anti-shudder performance, is highly dependent on friction modifiers and other additives in automatic transmission fluids (ATFs). These additives, in a manner similar to engine oil additives, are expected to interact with the steel and clutch material surfaces to form surface films that provide the desired performance. Hence, understanding the tribochemical processes in this automatic transmission system is a very important step towards performance optimisation. While the tribochemistry of engine oil additives and the nature of tribofilms on metallic surfaces are relatively well researched, the tribochemistry of ATFs still remains largely unclear. One reason for this is the level of complexity in analysing the friction materials of automatic transmission systems. Separating lubricant-derived species from the composite clutch friction materials is not trivial.This paper presents a comprehensive look at the tribochemistry of a new friction modifier in ATF systems and assesses the nature of the tribofilms formed on steel and composite friction materials in a variable speed friction test (VSFT) apparatus, which was used to simulate the clutch friction process. The tribofilm evolution is correlated with the tribological response as ageing occurs. Functional groups from the friction modifiers were found on the friction couple surfaces after the test and the mode of their action is discussed. These groups were proposed to form a layer of tribofilm on the top surface after rubbing. The correlation between observed tribochemistry processes and the tribological performance are discussed in detail.     

Valvetrain Friction Reduction through Thin Film Coatings and Polishing

In a direct-acting mechanical bucket tappet–type valvetrain, the cam and tappet contact is responsible for about 85% of the total valvetrain frictional losses. Because this contact operates primarily in a mixed lubrication regime, it offers an opportunity for friction reduction through surface engineering. The friction reduction potential of thin Mn-phosphate coating, diamond-like carbon coating, and polishing on the bucket surface was explored using a motored valvetrain rig equipped with 3.5L V6 engine head. The durability of tappets and cam lobes was also evaluated using a different motored valvetrain rig consisting of a single lobe and a single tappet. The polished buckets demonstrated substantial friction benefit over current production buckets at all speeds investigated. The diamond-like carbon coated buckets did not show any additional friction reduction benefit. The wear data demonstrated much less wear with polished buckets and also for cam lobes when in contact with polished buckets compared to current production buckets and cam lobes. The composition of antiwear surface films on polished buckets was found to be similar to that on current production buckets.     

设计动压向心滑动轴承的膜厚系数法

提出了膜厚系数和温升系数的概念，并给出了它们和长径比、相对偏心率的关系线图。利用这些线图，可以很方便地进行液体摩擦动压向心滑动轴承的设计。