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.     

The Lubricity of Gasoline

A study has been made of the lubricating properties of gasoline fuel. A conventional HFRR diesel fuel lubricity tester has been modified to measure gasoline wear. Using this test equipment, a number of features of gasoline lubricity have been investigated, including the comparative lubricating behavior of gasoline, the influence of detergent additives and oxygenates on wear and the wear behavior of a series of refinery streams employed in gasoline blending.

The lubricity of a range of pure organic chemicals known to be present in gasoline has also been studied. From these measurements it has been shown that, except for components such as dienes and diaromatics, the HFRR lubricating properties of most gasoline hydrocarbon constituents are broadly independent of chemical structure bur depend significantly on viscosity. Using these measurements, predictive wear equations based on gasoline group analysis have been developed.

Because it has been found that viscosity plays a role in determining the wear properties of gasoline, the elastohydrodynamic (EHD) film-forming and friction properties of gasoline have been measured and compared to those of diesel fuels. This shows that the combination of gasoline's very low viscosity and low pressure-viscosity coefficient results in very thin EHD film thickness generation and also very low friction in full-film EHD conditions.     

纳米蒙脱石添加剂对45~#钢摩擦副摩擦学性能的影响

将KH550偶联剂修饰的纳米蒙脱石(MMT)按不同质量分数加入150N基础油中,制备质量分数1%~5%的5种纳米MMT润滑油体系,采用MMU-10G摩擦磨损试验机考察纳米MMT对45#钢摩擦副减摩抗磨性能的影响,采用SEM和EDX等分析试样形貌与表面元素成分的变化,分析影响摩擦学性能的机制。结果表明:质量分数3%的纳米MMT润滑油和具有最好的抗磨减摩性能,相对于基础油润滑体系,可使金属摩擦副磨损失重量最小降低45.5%;所有试样表面均形成了以MMT特征元素和Fe元素为主体组成的自修复膜层,使试样磨损损失获得补偿,其中质量分数3%的纳米MMT润滑油润滑时摩擦副表面MMT特征元素的含量最高,故试样磨损率最小;纳米MMT润滑体系润滑时的摩擦因数均低于纯基础油,但是不同含量的纳米MMT对改善45#钢摩擦副的减摩性没有明显的区别。     

Silicon Nitride Boundary Lubrication: Effect of Oxygenates

A ball-on-three-flat (BTF) wear tester was used to investigate the boundary lubricating characteristics of oxygenates on a commercial silicon nitride. A wide variety of oxygen-containing compounds were tested neat and/or at 1% by weight in a paraffin oil. Compounds containing hydroxyl functional groups were more effective compared to a base case of neat paraffin oil. Decreases of up to 58% in friction coefficient, and 95% in wear were obtained. In most cases, films were observed in and around the wear scar, suggesting chemical reactions had taken place in the contact.

Additional wear tests, conducted using neat shorter-chain linear primary alcohols, i.e., 6–10 carbons, demonstrated boundary lubrication protection, with longer chain length providing better antiwear performance. A study of several C₈ compounds with specific oxygen-containing functional groups (primary alcohol, secondary alcohols, acid, aldehyde, and ketone) demonstrated that the primary alcohol had the strongest boundary lubricating effect. Varying the amount of water in the alcohols had little effect on friction and wear, suggesting that the boundary lubrication effects observed were not merely due to dissolved water in these fluids, but some characteristic chemical interaction with the hydroxyl functional group of the alcohols and acids.     

Experimental assessment of textured tools with nano-lubricants in orthogonal cutting of titanium alloy

In this study, we investigated the effects of composite nano-Cu/WS₂ lubricating oil and single-point diamond indentation-textures on improving the cutting performance of YG8 cemented carbide tools, which is crucial for textures tool applications. The aims of the study were to improve wear resistance and reduce chip adhesion at the tool’s rake face in cutting of titanium alloys. Dot textures with different spacings were fabricated on the surface of YG8 cemented carbide tools through the single-point diamond indentation method, and composite nano-Cu/WS₂ lubricating oil was prepared. Orthogonal cutting tests were carried out under dry cutting and minimal quantity lubricated (MQL) conditions. Investigate the effect of different texture spacing on the cutting performance in the light of cutting forces, friction coefficient, the deformed chip thickness, tool adhesions, and chip morphology. The results show that the dot texture effectively improved the lubrication conditions in machining titanium alloys under the MQL conditions. The dot texture is effective at low speed in the dry cutting conditions. With the increase of cutting speed, the friction coefficient of dot texture tool is affected by texture spacing, and the friction coefficient of DT-200 tool is the smallest. In addition, composite nano Cu/WS₂ lubricating oil forms a lubricating film on the wear path by atomizing the lubricating oil and stores it in the dot texture, which enhances the anti-wear performance in the cutting process and reduces the cutting force and friction coefficient at the tool chip interface. By evaluating cutting force, friction coefficient, chip and tool morphology, it is concluded that DT-100 tool is more effective in improving lubrication conditions.

     

润滑条件对纳米SiO2填充尼龙复合材料摩擦学性能的影响

利用MM-200磨损实验机在干摩擦、水润滑和油润滑等条件下，研究了润滑条件对含量为10％的纳米SiO2填充尼龙1010复合材料与45^#钢对磨时的摩擦学性能的影响，并利用扫描电子显微镜对纳米SiO2-PA1010复合材料的磨损表面和磨损机理进行了观察和分析。结果表明水润滑时，纳米SiO2-PA1010复合材料的摩擦因数比在干摩擦时有一定程度的降低，但磨损量却比干摩擦时增加了很多；而在油润滑时，摩擦因数和磨损量均比干摩擦和水润滑时降低了许多；复合材料的磨损机制也随着润滑条件的不同发生了相应的变化。     

An investigation on tribological properties of graphite nanosheets as oil additive

Graphite nanosheets with average diameter of 500 nm and thickness about 15 nm were prepared by stirring ball milling. The tribological behavior of the graphite nanosheets as additive in paraffin oil were investigated with a four-ball and a pin-on-disk friction and wear tester. The wear surfaces of the steel ball lubricated with the additive-containing paraffin oil were analyzed by means of scanning electron microscopy (SEM). It has been found that the graphite nanosheets as additive in oil at proper concentration show better tribological properties than pure paraffin oil. The load-carrying capacity and antiwear ability of the lubricating oil were improved. Moreover, the friction coefficient of the lubricating oil was decreased by the addition of the graphite nanosheets. The optimal concentration of the additive in paraffin oil is about 1.0 × 10⁻² wt.%.     

The Conduction of Current in Bearings

The mechanism of the action of sulfur compounds during boundary lubrication has been studied by using S³⁵ as a tracer. A NACA type friction machine was used to study the chemical reaction between elementary sulfur or sulfur compounds and metals. All additives were added to cetane which was used as a lubricating oil.

It has been found that it is possible to study kinetically the formation of the iron sulfide and the rate of the wear of its film on the friction surface. Some good analytical results have been obtained.

The rate of wear of iron sulfide film for benzyl disulfide is lower than that for the elementary sulfur, because the former may adsorb effectively to the worn surface. The iron sulfide film formed on the friction surface seems to absorb the polar compounds more actively than the surface of iron oxide. These results Were revealed from the autoradiography of the adsorption.     

用SRV试验机评价柴油机油摩擦磨损性能

采用SRV^?4型摩擦磨损试验机为试验平台,以某商用车公司提供的发动机缸套-活塞环截取件作为摩擦副试验件,以15W-40 CF-4和15W-40 CI-4发动机油为润滑介质,建立评价柴油机油摩擦磨损性能的模拟试验方法,并使用该方法对油品配方中减摩剂的区分性及不同材质活塞环与润滑油的适配性等进行考察。试验结果表明:建立的模拟试验方法能较好地区分出具有优异抗磨性能的柴油机油,同样对油品配方中减摩剂和不同材质活塞环与润滑油适配性等有着较好的区分性,可以作为润滑油品开发者和OEM汽车厂家对油品配方开发和摩擦副材质筛选的模拟评价手段。     

润滑油纷乱中甄选——

工程机械润滑油的作用主要是在机械上发生相对运动的摩擦机件上形成油膜，使机构间的干摩擦变成油层之间的液体摩擦，减小摩擦阻力，减少机件磨损。同时，工程机械润滑油还起到冷却、清洗、密封、防锈和消除冲击负荷等作用。但是，由于各种原因，致使很多用户经常买到假冒或者劣质润滑油，或者选择的润滑油种类不符合设备的使用要求，导致设备润滑不良而发生机械故障，影响设备的使用寿命，给用户带来经济损失。本期我们就来分析和探讨如何为工程机械选择合格的、恰当的润滑油。     

Valvetrain Friction and Wear Performance of Polyalkylene Glycol Engine Oils

The application of polyalkylene glycol (PAG) as a base stock for engine oil formulation has been explored for substantial fuel economy gains over traditional formulations with mineral oils. Various PAG chemistries were explored by varying the feedstock material. All but one formulation have the same additive package. The friction performance of these oils was evaluated in a motored valvetrain rig with current production engine hardware in the temperature range 40–100°C and in the speed range 300–2,500 rpm. PAG formulations showed up to 48% friction reduction over GF-5 SAE 5W-20 oil depending on temperature, speed, and oil chemistry. The wear protection capability was evaluated using a radiotracer technique on another motored valvetrain rig where only one cam lobe rotated against a bucket tappet. The wear trend of some PAG oils was equal to or better than that of GF-5 SAE 5W-20 oil, whereas others showed high initial wear. The wear rate of the PAG oils was not significantly different from that of GF-5 oil. The bucket tappet surfaces were analyzed using scanning electron microscopy, auger electron spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectroscopy to characterize the tribofilm formed and to help explain the friction and wear performance.     

Solution and analysis of VL combined seal lubrication model under the effect of wear

Through the finite element calculation of VL combined seal models under different wear conditions, contact pressure distributions of models are obtained. Considering the coupling effect between seal deformation and lubricating oil film, a mathematical model of elastohydrodynamic lubrication for VL combined seal is established. Based on the theory of small deformation, the elastic deformation of VL composite seal under high pressure is obtained by the deformation influence coefficient matrix method. Considering the influence of sealing surface wear and surface roughness, the oil film thickness distribution and oil film pressure distribution of VL combined seal are solved by the finite difference method. The analysis results show the wear of VL combined seal, the decrease of viscosity, the increase of roughness and rotational speed can raise the thickness and pressure of lubricating oil film. The correctness of numerical simulation is verified by experimentally measuring the friction torque and leakage rate of seal.

     

Ultrasonic machining of engine lubricating oil during tribotechnical testing

The results of tribotechnical testing of brass–steel and iron–steel friction couples for both their running-in ability and wear resistance have been described. For brass and iron jaws of friction couples, it has been established that the load before tearing increased to 4.3 and 12.3%, respectively, in synthetic oil, while for semisynthetic oil, it increased to 12.5 and 25.0%. It has also been found that ultrasonic machining enabled a decrease in the coefficient of friction for brass and iron jaws in synthetic oil to 13.4 and 15.3%, respectively, and 25.0 and 28.1% in semisynthetic oil. Any features of the residual viscosity of engine lubricating oil after ultrasonic machining, which cannot be measured with a fluidmeter, have been found.     

Further investigation on the tribological behavior of Al2O3–20Ag20CaF2 composite at 650°C

The friction and wear behaviors of the self‐lubricating Al₂O₃–20Ag20CaF₂ disk against an Al₂O₃ pin pair have been investigated over a broad load range from 1 to 30 N and sliding velocities from 0.084 to 1 m/s at 650^°C. Four typical wear modes have been identified and the wear mode map was constructed to illustrate the influence of load and speed on the friction coefficient and wear rate. The results showed the effective self‐lubricating region (II) (continuous lubricating film) is almost independent of sliding speed, and mainly dependent on the load. It is suggested that the plastic deformation and plastic flow during sliding play an important role in the formation of the self‐lubricating film on the sliding surface. Furthermore, the worn surface in the region (II) (continuous lubricating film) was found to be much softer than the original surface and the distribution of Vickers hardness became more uniform due to the presence of the lubricating film on the worn surface. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of lubricants on the friction and wear of Al2O3 against gray cast iron

The tribological behavior of ceramic Al₂O₃ coupled with gray cast iron (PHT) with different lubricants was investigated using a ring-on-block wear tester. In the wear test, air, distilled water, emulsion and oil were used as lubricants respectively in order to check the lubricating effectiveness of lubricants and the friction mechanism of solid graphite in the cast iron. Wear testing of 0.8% C steel (T8) sliding with Al₂O₃ was also carried out to compare with the test using gray cast iron. From these data the tribological behavior of graphite in the iron can be evaluated. The results show that the friction and wear of tested couples are decreased using different lubricants in the following order: air, distilled water, emulsion and oil. When lubricating with air and water, graphite in the iron as solid lubricant can decrease the friction and wear of the couples. However, when lubricating with emulsion and oil, graphite does not show the advantage of decreasing friction and wear.     

纳米碳球作为合成酯抗磨剂的摩擦学性能研究

采用表面化学改性的方法得到硬脂酸修饰的纳米碳球,在四球摩擦试验机上考察纳米碳球在合成酯类润滑油中的抗摩擦性能,探讨纳米碳球的抗磨与润滑机制。结果表明,通过表面改性,显著提高纳米碳球在润滑油中的分散稳定性;纳米碳球作为合成酯润滑油抗磨剂表现出优良的抗磨减摩性能;在转速1.200 r/min,载荷150 N的实验条件下,质量分数0.07%的改性纳米碳球可使三羟甲基丙烷混酸酯平均摩擦因数减小幅度达到30%左右,磨损率降低33%,质量分数0.15%的改性纳米碳球可使季戊四醇油酸酯的平均摩擦因数降低幅度达到50%以上,磨损率降低14.6%     

离子液体对WS2纳米润滑油摩擦学性能的影响

纳米二硫化钨的润滑性能优异,但由于其在润滑油中易团聚沉降,影响了其在润滑油中抗磨减摩性能的发挥。为改善纳米WS2的抗磨减摩性能,将一种磷酸盐离子液体添加到WS2纳米润滑油中,通过四球摩擦试验机对其摩擦学性能进行测试,采用XPS、EDS和电子显微镜等表征方法对钢球磨损表面进行表征。结果表明：虽然添加离子液体后纳米润滑油的摩擦因数略微上升,但相对基础油,离子液体仍可使其摩擦因数最大降低28%,同时能显著地减小磨斑直径,最大降幅达到了44%。离子液体在摩擦过程中与WS2反应生成PW,该物质作为催化剂加速了摩擦过程中的氧化反应,生成的化合物作为化学摩擦膜减少磨损,提升润滑油抗磨减摩性能。     

重型汽车中桥减速器润滑油中磨损颗粒分析

重型汽车中桥减速器在工作过程中其摩擦副接触表面因相对运动而产生的磨损颗粒进入润滑油中,导致润滑油性能下降;磨损颗粒随润滑油进入摩擦副接触表面,摩擦副磨损加剧。根据重型汽车的运行特点,每隔一定里程数对减速器润滑油进行取样,综合分析在用润滑油中磨损颗粒物的大小、形貌及成分。结果表明：减速器在用润滑油中磨损颗粒主要成分是铁屑和铜屑,磨损颗粒主要来自于球面垫片（铜）及其配副的摩擦以及齿轮副间的摩擦。具体分析磨损颗粒产生过程及形成机制,为重型汽车中桥减速器中运动摩擦副的设计及制造提供理论依据。     

Effect of Bio-Lubricant and Biodiesel-Contaminated Lubricant on Tribological Behavior of Cylinder Liner–Piston Ring Combination

This article addresses the issue of friction and wear characteristics of diesel engine cylinder liner–piston ring combinations under different lubricating conditions using a pin-on-disc wear tribometer. The discs were made out of actual engine cylinder liner material using a casting process. Pins were made out of top compression ring material. The tests were conducted on a pin-on-disc tribometer for wear and friction characteristics of the cylinder liner and piston ring combination with diesel-contaminated rapeseed oil–based bio-lubricant, diesel-contaminated commercial synthetic lubrication oil (SAE 20W40), biodiesel-contaminated commercial synthetic lubrication oil (SAE 20W40), and used (150 h) commercial synthetic lubrication oil (SAE 20W40). Experimental results demonstrated that the rapeseed oil–based bio-lubricant and biodiesel-contaminated synthetic lubricant exhibited better performance in terms of wear, friction, and frictional force under similar operating conditions. Thus, usage of newly formulated bio-lubricant and biodiesel in the long run may have a positive impact on engine life.     

Palm oil and mineral oil based lubricants—their tribological and emission performance

A comparative study of wear, friction, viscosity, lubricant degradation and exhaust emissions was carried out on a palm oil and a mineral oil-based commercial lubricating oil. The wear and friction test was at first conducted using a reciprocating universal wear machine followed by a two-stroke gasoline Yamaha portable generator set, ET 950. The test conditions for the bench test were: pressure, 3.0 MPa; sliding speed, 0.20 m s⁻¹; sliding stroke, 80 mm; room temperature, 25°C. The test conditions for the actual engine were: constant load, 0.4 kW for wear of the piston ring but various loads for exhaust emissions and constant speed, 2800 rpm. Analysis of post bench test lubricating oils was performed using ISL viscometer, TAN/TBN analyzer and FT-IR spectroscopy to investigate viscosity, TAN value and the oxidation level, respectively. Exhaust emission analysis was also performed using a BOSCH exhaust gas analyzer. Experimental results demonstrated that the palm oil based lubricating oil exhibited better performance in terms of wears, and that the mineral oil based lubricating oil exhibited better performance in terms of friction. However, the palm oil based lubricant was the more effective in reducing the emmission levels of CO and hydrocarbon.