Tribological Analysis of a Hydrodynamic Journal Bearing under the Influence of Synthetic and Biolubricants

This study investigated the tribological characteristics of journal bearings exclusively for automotive applications under the influence of a synthetic lubricant (SAE20W40) and chemically modified rapeseed oil (CMRO) as a biolubricant, dispersed with TiO₂, WS₂, and CuO nanoparticles used as antiwear additive. The effects of synthetic and nanobased biolubricants on the tribological behavior of the hydrodynamic journal bearing were examined using a journal bearing test rig by measuring the coefficient of friction, oil film thickness, and wear under a load of 10 kN and a speed of 3,000 rpm. The test results show that CuO nanoadditives that are added to the biolubricant exhibit outstanding wear and friction reduction behavior, better than that with synthetic lubricants as well as other nanobased biolubricants. The inclusion of CuO nanoparticles in the biolubricant decreased the coefficient of friction by 27% and wear by about 47% compared to a synthetic lubricant. Additionally, investigations were performed using atomic force microscopy (AFM) and scanning electron microscopy (SEM) to study the surface morphology and surface roughness behavior of the tested bearing surfaces.     

Wear and friction of synthetic esters in a boundary lubricated journal bearing

This study concerns the case of a slow intermittent motion, conformal contact, high load bronze journal bearing against a hardened steel shaft lubricated in an oil bath at a temperature about of 13 °C. Three synthetic esters were used: one pure and two formulated ones. Worn surfaces were examined using SEM-EDS to determine the wear mechanism. The tested lubricants were examined using ICP-AES to identify the elements present.The results show the wear rate, friction and temperature in the subsurface of the journal bearing material. An initial bronze–steel contact develops into a copper–copper contact along the sliding distance. Wear element concentration in the oil and friction surfaces departs from the elementary concentration in the journal bearing bronze base material. The copper layer thickness depended on additives in the synthetic esters, load and wear rate.     

Effect of nanosilica additive particles on both friction and wear performance of mild steel/CuSn/SnBi multimaterial system

This paper presents an experimental study of the tribological behaviour of a multimaterial system using conventional powder metallurgy process with SiO₂ nanoparticles. Four configurations were studied with and without SiO₂. The tribological properties of the sintered materials were analysed by wear experiments at lubricated conditions on a ball disc wear test rig. The results are compared with those of conventional material for journal bearing. These show less variation of the friction coefficient and less wear rate for the materials with SiO₂ compared to the ones without SiO₂ and to those of the reference material. The dominant wear mechanism is adhesive wear, accompanied by mild abrasive wear.     

Tribological behaviour of steel‐alumina sliding pairs under boundary lubrication conditions

The tribological behaviour of oil‐lubricated steel‐alumina sliding pairs was investigated using a ball‐on‐disc tribometer at room temperature. Commercial bearing balls of 10 mm diameter were mated to 99.7% Al₂O₃ discs, and additive‐free mineral oil was fed into the contact area. The sliding speed and the applied normal load were varied, and the initial surface roughness of the Al₂O₃ disc was altered using different polishing and grinding procedures. The results showed that the surface roughness of the ceramic discs dominated the tribological behaviour under the given experimental conditions. The sliding speed as well as the normal load showed less effect on the friction behaviour, but the amount of wear depended strongly on the normal load. From the results it was concluded that improvement of the surface roughness and optimised surface machining of the ceramic material can be essential for improving the tribological performance for boundary‐lubricated steel‐ceramic sliding pairs.     

Tribological Performance of CuPb Alloy under Seawater Lubrication

In this article, the tribological behaviors of Cu–30wt% Pb (denoted as CuPb) alloy sliding against aluminum bronze ZCuAl9Mn2 lubricated by seawater were investigated. It was found that the friction coefficients decrease with increasing load and sliding speed, and the wear rates increase slightly with applied load but decrease with sliding speed. The low friction coefficient and wear rate can be attributed to the seawater as a lubrication medium, which has lubricating, cooling, and corrosive effects on the sliding couple.     

Friction and wear properties of Babbitt alloy 16-16-2 under sea water environment

The tribological behaviors of Babbitt alloy 16-16-2 sliding against aluminum bronze ZCuAl9Mn2 lubricated by sea water were systematically investigated in this paper. The results indicated that the friction coefficient decreased as the load increased to 30 N and then remained at a steady level at high loads, but decreased with increase in sliding speed. The wear rate increased with load, but decreased with sliding speed. The formation of basic lead carbonate Pb₃(OH)₂(CO₃)₂ during the sliding process played a critical role in the remaining low friction coefficient in sea water.     

黄铜全流量在线磨粒静电监测实验研究

为深入了解静电监测方法对黄铜的监测能力,采用自制的全流量在线磨粒静电传感器开展黄铜的静电监测方法研究。研究了润滑条件下轴承钢-黄铜滑动摩擦荷电磨粒的产生机理并设计了磨粒静电监测系统,开展了三种尺寸的轴承钢球和黄铜球的单颗粒注入实验、双颗粒注入实验以及相同载荷、不同滑动速度的轴承钢-黄铜滑动摩擦磨损实验,对摩擦因数、静电感应信号、静电信号均方根值进行相关性分析。研究结果表明:全流量在线磨粒静电传感器具有较好的检测一致性;静电监测方法对黄铜的监测能力强于对轴承钢的监测能力;摩擦因数与静电监测信号具有相关性,在磨损阶段,静电感应信号出现脉冲尖峰与持续上升。     

Embeddability behaviour of some Pb-free engine bearing materials in the presence of abrasive particles in engine oil

One of the tribological requirements on engine bearing material is its ability to safely embed contaminant particles onto its surface and minimise damage to both the bearing and crankshaft surfaces. In this work, a journal bearing test rig that operates under constant load has been employed to investigate the embeddability behaviour of selected multi-layered Pb-free engine bearing materials at three different rotational speeds using engine oil contaminated with SiC particles. Experimental results have shown that third-body abrasive wear is influenced by the lubricant film thickness. There was also difference in embeddability of the different materials. Bismuth-based overlay and MoS₂ containing polyamide-imide-based overlay-coated materials show higher wear compared to tin-based overlay and a polyamide-imide-based composite overlay-coated material. Steel counter surfaces sliding against bismuth-based overlay and MoS₂ containing polyamide-imide-based overlay exhibited higher wear than those sliding against tin-based overlay and polyamide-imide-based composite overlay.     

Tribological Behaviour of Polymeric Coatings: II. SCF‐Reinforced PEEK Nanocomposite Systems

This paper focuses on coatings based on poly(ether ether ketone) (PEEK) applied to metal substrates and their tribological investigation. Short carbon fibres (SCF), graphite, and 300 nm titanium dioxide (TiO₂) and zinc sulphide (ZnS) particles were used as filler materials for the PEEK. These filler materials and their combinations were found to have a significant influence on the tribological behaviour of the corresponding PEEK compounds. One of the compounds (PEEK6) was found, especially at higher temperatures and under higher normal loads, to be a good coating material showing superior tribological behaviour. For PEEK6, a specific wear rate and a coefficient of friction (COF) lower than those for the best commercially available PEEK compound (PEEK4) were measured. For specific test parameters, PEEK6 showed a COF of less than 0.1. The tribological results were also compared with those of a conventional sliding bearing material based on poly(vinylidene fluoride) (PVDF).     

Tribological Properties of Phosphor Bronze and Nanocrystalline Nickel Coatings Under PAO + MoDTC and Ionic Liquid Lubricated Condition

The friction and wear properties of phosphor bronze and nanocrystalline nickel coatings were evaluated using a reciprocating ball-on-plates UMT-2MT sliding tester lubricated with ionic liquid and poly-alpha-olefin containing molybdenum dialkyl dithiocarbamate, respectively. The morphologies of the worn surfaces for the phosphor bronze and nanocrystalline nickel coatings were observed using a scanning electron microscope. The chemical states of several typical elements on the worn surfaces were examined by means of X-ray photoelectron spectroscopy. Results show that the phosphor bronze and nanocrystalline nickel coatings exhibited quite different tribological behaviors under different lubricants. Phosphor bronze plate shows higher friction coefficient (0.14) and wear rate (3.2 × 10⁻⁵ mm³/Nm) than nanocrystalline nickel coatings (average friction coefficient is 0.097, wear rate is 1.75 × 10⁻⁶ mm³/Nm) under poly-alpha-olefin containing molybdenum dialkyl dithiocarbamate lubricated conditions. The excellent tribological performance of nanocrystalline nickel coatings under above lubricant can be attributed to the formation of MoS₂ and MoO₃ on the sliding surface. a quite a number of C, O and F products on worn surface of phosphor bronze than NC nickel coatings can improve anti-wear properties while using ionic liquid as lubricant.     

Wear properties of Saffil/Al,Saffil/Al2O3/Al and Saffil/SiC/Al hybrid metal matrix composites

The purpose of this study is to investigate the wear properties of Saffil/Al, Saffil/Al₂O₃/Al and Saffil/SiC/Al hybrid metal matrix composites (MMCs) fabricated by squeeze casting method. Wear tests were done on a pin-on-disk friction and wear tester under both dry and lubricated conditions. The wear properties of the three composites were evaluated in many respects. The effects of Saffil fibers, Al₂O₃ particles and SiC particles on the wear behavior of the composites were elucidated. Wear mechanisms were analyzed by observing the worn surfaces of the composites. The variation of coefficient of friction (COF) during the wear process was recorded by using a computer. Under dry sliding condition, Saffil/SiC/Al showed the best wear resistance under high temperature and high load, while the wear resistances of Saffil/Al and Saffil/Al₂O₃/Al were very similar. Under dry sliding condition, the dominant wear mechanism was abrasive wear under mild load and room temperature, and the dominant wear mechanism changed to adhesive wear as load or temperature increased. Molten wear occurred at high temperature. Compared with the dry sliding condition, all three composites showed excellent wear resistance when lubricated by liquid paraffin. Under lubricated condition, Saffil/Al showed the best wear resistance among them, and its COF value was the smallest. The dominant wear mechanism of the composites under lubricated condition was microploughing, but microcracking also occurred to them to different extents.     

Tribological Effects of Vegetable Oil as Alternative Lubricant: A Pin-on-Disk Tribometer and Wear Study

The investigation of lubricated friction and wear is an extended study. The aim of this study is to investigate the friction and wear characteristics of double fractionated palm oil (DFPO) as a biolubricant using a pin-on-disk tribotester under loads of 50 and 100 N with rotating speeds of 1, 2, 3, 4, and 5 ms^?1 in a 1-h operation time. In this study, hydraulic oil and engine oil (SAE 40) were used as reference base lubricants. The experiment was conducted using aluminum pins and an SKD 11(alloy tool steel) disc lubricated with test lubricants. To investigate the wear and friction behavior, images of the worn surface were taken by optical microscopy. From the experimental results, the coefficient of friction (COF) rose when the sliding speed and load were high. In addition, the wear rate for a load of 100 N for all lubricants was almost always higher compared to lubricant with a load of 50 N. The results of this experiment reveal that the palm oil lubricant can be used as a lubricating oil, which would help to reduce the global demand for petroleum-based lubricants substantially.     

Abrasive wear of bearing materials — a comparison of test methods

In a lubricated journal bearing, journal as well as bearing may suffer from wear if the lubricant contains hard abrasive particles. Wear may be particularly severe under conditions of boundary lubrication. Tests with 360° journal bearings show that, as far as friction and wear are concerned, the white metal SnSb8Cu4Cd and the bronze CuPb10Sn10 suffer equally from the addition of “air cleaner test dust” in the lubricant. In contrast, on addition of the abrasive, the composite process surface roughness of the bearing (which controls the ability of the bearing to re-establish thick film lubrication) remains virtually unaffected in the case of the white metal but increases considerably in the case of the bronze.The results of tests, performed with a block-on-ring method, do not agree well with those found with real journal bearings. Thus they are not suitable for qualifying materials for application in journal bearings lubricated with abrasive-containing lubricant.     

Assessment and application of TiB2 coating in sliding pair under lubrication conditions

The aim of the present work is to determine the influence of TiB₂ coating on the friction parameters in sliding pairs under lubricated friction conditions. The TiB₂ coating deposited on modified surface layers of ring specimens made of AISI 5045 steel was matched under test conditions with counterparts made from SAE-783 and SAE-48 bearing alloys. Tested sliding pairs were lubricated with 5 W/40 Lotos synthetic engine oil. Tribological properties of the TiB₂ coating were measured using a block-on-ring tribometer. The applied modification technology of the surface layer of steel allowed for obtaining construction material with pre-determined tribological characteristics required for the elements of sliding pairs in lubricated contact. The results showed differences in the wear of bearing alloys, as a result of the interaction between co-operating surface layers and of the physiochemical changes of their surfaces, induced by external forces. Friction resistance and temperature in the friction area in the pair with TiB₂ coating and the SAE-783 bearing alloy are considerably higher than in the pair with the SAE-48 bearing alloy. The SAE-48 bearing alloy is subjected to more intensive wear processes in contact with the TiB₂ coating than the SAE-783 bearing alloy.     

Electrical and tribological properties of composite material with copper matrix reinforced by superelastic hard carbon

Electrical and tribological properties of a copper-based composite material reinforced by superelastic hard carbon particles are studied. Composite material specimens have been produced using the hightemperature pressing of mixtures of copper and fullerene powders. Electrical and tribological reciprocal tests carried out using the plane-on-plane arrangement have shown that the coefficient of friction of the composite material–Ni pair is lower than that of the reference L63 brass–Ni pair at similar values of contact electrical resistance. The abrasive wear resistance of the composite material is 40 times higher than that of brass. The developed copper-based composite materials reinforced by superelastic carbon particles hold promise for use in sliding electrical contacts.     

添加剂对聚氨酯材料摩擦性能的影响

为改善聚氨酯水润滑轴承材料的性能,在聚氨酯预聚体中分别添加不同含量的润滑脂、消泡剂和合成蜡,制备3种聚氨酯复合材料;利用CBZ-1型船舶轴系摩擦磨损试验机测试复合材料在不同工况下的摩擦学性能,利用激光干涉位移表面轮廓仪和超景深显微镜观察不同聚氨酯复合材料对摩副的表面形貌,探讨材料在水润滑条件下的磨损机制。结果表明:润滑脂和消泡剂的添加提高了聚氨酯材料的稳定性,再添加合成蜡有效地改善其在高压工况下的润滑状态;在高压工况下,与纯聚氨酯材料对摩的铸铜盘磨损后出现犁沟现象,表现出磨粒磨损的特征并伴随着黏着磨损,而与复合聚氨酯材料对摩的铸铜盘磨损后仅出现黏着磨损的特征。润滑脂、消泡剂和合成蜡能有效提高聚氨酯材料的耐磨性以及降低对摩副的磨损损耗,从而提高了聚氨酯材料作为水润滑轴承的安全性和可靠性。     

Tribological Characteristics of Rubber-Based Friction Materials

This article deals with the rubber-based friction materials (RBFMs) which can be used in brake system. The physico-mechanical and tribological properties of a series of fiber filled RBFMs containing steel wool and aramid pulp at different concentrations along with a fiber-free reference material were characterized. Rubber–glass transition induced at higher sliding velocities was identified based on the friction fade behavior of the RBFMs. The rubber–glass transition which is inherently originated by viscoelastic response of polymeric binder was found to be influential on the tribological properties of the RBFMs. It was revealed that steel wool increased coefficient of friction (COF) and improved friction recovery behavior at low volume percent (7.5 vol.%) but it aggravated the COF at high concentration of steel wool (15 vol.%) and severe sliding conditions because of harsh abrasive mechanism. Aramid pulp improved the fade behavior at high sliding velocities and increased COF due to formation of sticky contact patches. It was revealed that steel wool increased the wear rate while aramid pulp did not affect the wear rate significantly, contrary to the increase in the friction coefficient of RBFM. SEM analysis was proved to be useful in correlating the wear rates of composites to the topographical changes on the worn surfaces.     

Friction and Wear Behavior of Irradiated Polyethylene Sliding Against a Rough Steel Surface

The aim of this study was to evaluate the tribological behavior of polyethylene crosslinked by gamma radiation sliding against a steel surface. Two high-density polyethylenes were irradiated to a total dose in the range of 2?20 Mrad under vacuum and at room temperature. After irradiation, the materials were annealed at 423 K and then cooled slowly to room temperature. The same thermal treatment was applied to the non-irradiated polymer. The wear behavior of the polymers was determined under controlled ambient temperature of 298 and 333 K using a homemade tribometer. Sheet-shaped specimens were loaded against the surface of a steel disc with different normal loads to generate nominal contact pressures in the range of 0.25–1.5 MPa. The tests were performed under dry conditions using a disc rotation to produce an average sliding speed of 0.6 m/s and during a period of time to provide an average sliding distance of 1,080 m. The wear rate was obtained as the mass loss by the sample divided by the sliding distance, and the friction coefficient was determined by measuring the friction force. The results indicate that the wear rate increases with load in the case of non-irradiated polyethylene and low-dose irradiated polymers, while the wear rate reaches a maximum value with the load in the case of the irradiated samples with high doses. The samples irradiated with a dose of 10 Mrad showed the lowest wear. The coefficient of friction (COF) increases slightly with the load in all the cases. Most irradiated polymers show higher COF than the non-irradiated material when compared at a given load. The results show that the irradiation dose applied to the polyethylenes produced no noticeable effect on the COF values when a comparison was made at a given applied load.     

Ultralow Friction Behaviors of Hydrogenated Fullerene-Like Carbon Films: Effect of Normal Load and Surface Tribochemistry

Friction and wear behaviors of hydrogenated fullerene-like (H-FLC) carbon films sliding against Si₃N₄ ceramic balls were performed at different contact loads from 1 to 20 N on a reciprocating sliding tribometer in air. It was found that the films exhibited non-Amontonian friction behaviors, the coefficient of friction (COF) decreased with normal contact load increasing: the COF was ~0.112 at 1 N contact load, and deceased to ultralow value (~0.009) at 20 N load. The main mechanism responsible for low friction and wear under varying contact pressure is governed by hydrogenated carbon transfer film that formed and resided at the sliding interfaces. In addition, the unique fullerene-like structures induce well elastic property of the H-FLC films (elastic recovery 78%), which benefits the high load tolerance and induces the low wear rate in air condition. For the film with an ultralow COF of 0.009 tested under 20 N load in air, time of flight secondary ion mass spectrometry (ToF-SIMS) signals collected inside and outside the wear tracks indicated the presence of C₂H₃ ⁻ and C₂H₅ ⁻ fragments after tribological tests on the H-FLC films surface. We think that the tribochemistry and elastic property of the H-FLC films is responsible for the observed friction behaviors, the high load tolerance, and chemical inertness of hydrogenated carbon-containing transfer films instead of the graphitization of transfer films is responsible for the steady-state low coefficients of friction, wear, and interfacial shear stress.     

Wear and friction of filled polyamide coatings

The aim of this article is to report wear and friction studies of cylindrical test steel pins coated with polyamide (PA6) incorporating fillers (iron, copper, aluminium, tin, lead) and solid lubricants (graphite, molybdenum disulphide (MoS₂)) to improve the mechanical, thermal, and frictional properties of polyamide (PA6). The coated testpins were loaded against a rotating cylinder of bearing steel in dry, lubricated, abrasive conditions at constant load and sliding speed. The test results show a significant reduction in wear and friction for both copper-filled polyamides and lead-filled polyamides.