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2018, Lubrication science
https://doi.org/10.1002/LS.1408…
14 pages
1 file
This work aims to study the effect of solid lubrication combined with a liquid lubricant in a cooperative lubrication regime. The solid lubricant consists of sintered composites, which contain solid lubricant dispersed in a metallic matrix. The durability of the lubricious regime (μ < 0.2) was studied. The combined action significantly increased the durability of the lubricious regime (3 orders of magnitude). Additionally, the use of 3D triboscopy made it possible, using an original approach, to verify a significant increase in the friction coefficient at the dead centres of the strokes. This difference between the friction coefficients was discussed in terms of the debris accumulation and the change in the lubrication regime. A preponderant role was assigned to the accumulation of debris.
The reduction of the interfacial friction between two surfaces in relative motion is a prerequisite for the proper functioning of many systems, ranging from machine parts to human joints. While the lubrication of two contacting surfaces primarily aims at the reduction of friction and wear, either by a separation of the surfaces by means of a fluid film or by introducing a layer of low shear strength between them, additional requirements such as the environmental compatibility of a lubricant or the energy efficiency of tribological systems have become important during recent years. This paper is limited to a discussion of the solid lubricants which comprise probably the largest single area. Although methods of attaching a lubricating solid to a wearing surface are many and vary considerably, the end result is the same, that is, a low friction medium is deposited to reduce friction and wear between two relatively moving surfaces under essentially dry conditions.
Wear, 2007
Solid lubricant films based on MoS 2 and WS 2 are widely used for dry air friction and aerospace applications. Different plasma deposition methods are widely used for formation of solid lubricant films on the contact surfaces. One of the simple methods of solid lubricant film deposition is cloth burnishing. The aim of this work is to develop new simple methods for burnishing of steel surfaces providing improved the tribological properties of solid lubricant films. For this cause the solid lubricant particles were burnished by the loading system of balls. MoS 2 as well as some binders were used for formation of lubricant layer. In order to improve the consolidation of particles in the layer, external excitation of loading system has been used. The friction coefficient and the longevity of solid lubricant film were assessed using ball-on-flat and pin-on-disk devices. The effect of burnished films on their tribological properties is discussed.
Advanced Rheology and Its Applications [Working Title]
Solid lubricants separate two moving surfaces and reduce wear. Materials’ ability to act as solid lubricants depends on their characteristics relative to contact surfaces. Chemically stable fluorides (BaF2, CaF2), boron nitride (h-BN), transition metallic sulphides (MoS2, WS2), soft metals (Au, Ag), binary and multi-component oxides, such as silver-containing sulphates, chromates, and oxides, and MXenes are effective solid lubricants. Solid lubrication depends on the material’s structure. Structure, mechanical properties, chemical reactivity, and kind of substance characterise these materials (refractories, ceramics, glass, etc.). High temperatures (>300°C) are obtained at asperities due to frictional heat produced when two surfaces rub. High temperatures can breakdown lubricants, but the resulting compounds must be lubricants; otherwise, corrosive vapours or abrasive solids can occur. High thermal conductivity helps lubricants remove heat generated by rubbing. Lubricants must no...
Wear, 1972
The object of this investigation was to determine the effect of lubricant film thickness on the coefficient of friction and on the wear life of solid lubricants. Bonded molybdenum disulphide and bonded graphite were the lubricants tested. Dow Corning's LFW-1 and Falex lubricant tester were the two machines used for testing these lubricants. The lubricants were sprayed on the specimen surface. ll Pretreatment, spraying and curlng were done according to standard or manufacturer's recommended procedures. During the entire research, the procedure for experimentation was followed according to ASTM No. 2625 on Falex and CRC recommendations on LFW-1 machine. It was found that the film thickness lS an important factor in deciding performance of a solid lubricant. The coefficient of friction increases with increase in film thickness for thicknesses in the range tested (0.0017 in. to 0.0007 in.). For a maximum wear life, there is a definite optimum film thickness, above and below which the wear life decreases.
Friction
This work is a review of previous works, presenting and discussing the most important results obtained by an ongoing research program towards the development of innovative, low-cost, self-lubricating composites with a low friction coefficient and high mechanical strength and wear resistance. Special emphasis is given to uniaxial die pressing of solid lubricant particles mixed with matrix powders and to metal injection moulding associated with in situ generation of solid lubricant particles. Initially, a microstructural model/ processing route (powder injection moulding followed by plasma-assisted debinding and sintering) produced a homogeneous dispersion of in situ generated solid lubricant particles. Micrometric nodules of graphite with diameter smaller than 20 μm were formed, constituting a nanostructured stacking of graphite foils with nanometric thickness. Micro Raman analysis indicated that the graphite nodules were composed of turbostratic 2D graphite having highly misaligned graphene planes separated by large interlamellae distance. Large interplanar distance between the graphene foils and misalignment of these foils were confirmed by transmission electron microscopy and were, probably, the origin of the outstandingly low dry friction coefficient (0.04). The effect of sintering temperature, precursor content, metallic matrix composition and surface finish is also reported. Furthermore, the influence of a double-pressing/double-sintering (DPDS) technique on the tribological performance of self-lubricating uniaxially die-pressed hBN + graphite-Fe-Si-C-Mo composite is also investigated. Moreover, the tribological behaviour of die-pressed Fe-Si-C matrix composites containing 5, 7.5 and 10 wt% solid lubricants (hBN and graphite) added during the mixing step is analysed in terms of mechanical properties and wear mechanisms. Finally, the synergy between solid lubricant particles dispersed in a metallic matrix and fluid lubricants in a cooperative mixed lubrication regime is presented.
Machines, 2019
Increasing the lifetime of machine elements whose operation involves the development of friction processes and diminishing energy losses by friction can be achieved by using solid lubricants. In this regard, a method applied to improve the friction behavior of machine elements is electrostatic coating of the surfaces of interest with polyester layers that include particles of solid lubricants, such as molybdenum disulfide or graphite. Experimental research was conducted to highlight the influence of normal force, the concentration of solid lubricant particles in polyester, and specific sliding between surfaces involved in the friction process on the deposited layer’s lifetime and on the friction coefficient. Grey analysis was employed to identify sets of input factors that would lead to the most convenient values of the lifetime and energy friction losses when using polyester layers that incorporate molybdenum or graphite particles. Specialized software was elaborated in a MATLAB en...
1992
In a study seekingto achieve low friction and low wear on ceramic materials,we Investigateda new lubrication concept that exploresthe synergisticeffect of a silverfilm and a recentlydeveloped syntheticoil on the boundarylubricationbehaviorof siliconnitride(SisN4)ceramics.Frictionand wear testswere performedon a wear test machine at temperaturesupto 380°C. Under thetest conditionsexplored,we foundthat thefrictioncoefficientsof SisN4/SisN4 test pairsduringoil-lubricatedslidingtestsrangedfrom 0.1 to 0.35, and the averagewear rates of ceramicpinswere between3 x 10 "7 and 10.6 mm3 N"1 m1, dependingon test temperature.Concurrentuseof lubricantoil witha silver film had a synergisticeffecton both frictionand wear. Specifically,it was observedthat when silverfilmsare used at oil-lubricatedslidinginterfaces,the wear rates of both pins and flats were reduced to unmeasurablelevelsand the frictioncoefficientswere reduced by factorsof twoto ten belowthose of the test pairswithoutsilverfilms.Beneficial synergisticeffects of silverfilms and syntheticoil on the boundary-lubricationbehavior of ceramics were more pronouncedat elevatedtest temperaturesthanat room temperature.
2020
Lubricants are substances placed between two movable surfaces or a fixed and a movable one, forming a protective film whose main function is to reduce friction, wear, temperature and sealing of machine and motor components, and may also be a force transmission agent And movement. Therefore the objective of this work is to contribute to the construction of materials on the subject, aiming to analyze the types of lubricants, their characteristics, as well as the innovation in the sector. Thus, the applied methodology is mainly a literature review followed by an analysis. It should be noted that each type of lubricant is important for different types of equipment but is not yet in the state of the art and new technologies such as liquid crystal must be developed, which is highly efficient but still has a very high cost.
industrial crops and products, 2009
Coefficient of friction Dry-film lubricant Microscopy a b s t r a c t Aqueous dispersions of starch-soybean oil (SBO) and starch-jojoba oil (JO) composites, prepared by excess steam jet cooking, form effective dry film lubricants when applied as thick coatings to metal surfaces by a doctor blade. This application method necessitates long drying times, is wasteful, requires the addition of sucrose to promote composite adhesion to the metal surface, and restricts the substrate geometry to planar surfaces. These issues represent important barriers to the commercialization of this aqueous biobased dry film lubricant technology. We now report an air-assisted spray method that uses readily available spray equipment to apply aqueous starch-oil composite dispersions as thin coatings (0.15-2.0 mg/cm 2 ) to metal surfaces quickly and efficiently. Aqueous dispersions of waxy maize starch-oil composites containing either SBO, JO or hexadecane (HD), having 0.020-31.7 wt% oil relative to starch, were applied by air-assisted spraying and could be dried to the touch in approximately 30 s. Additionally, sucrose was found unnecessary for adhesion of the sprayed coatings. Tribological ball-on-flat testing of metal specimens spray coated with starch-SBO, -JO, and -HD composites showed the thin films of starch-SBO and -JO performed better at reducing the coefficient of friction (COF) than the starch-hexadecane composites. A low COF ranging between 0.027 and 0.044 was obtained for the starch-SBO and -JO composites containing 4-5 wt% oil relative to starch. Above 4-5 wt% oil loadings, no further COF reductions were realized. Further results revealed that micrometer-sized oil droplets embedded within the dried starch matrix of the composite film are delivered "on demand". It appears that when pressure is applied to the dry film lubricant, the starch matrix ruptures and releases the entrained oil to the friction surface.
Lubricants, 2014
The role of surface protective additives becomes vital when operating conditions become severe and moving components operate in a boundary lubrication regime. After protecting film is slowly removed by rubbing, it can regenerate through the tribochemical reaction of the additives at the contact. However, there are limitations about the regeneration of the protecting film when additives are totally consumed. On the other hand, there are a lot of hard coatings to protect the steel surface from wear. These can enable the functioning of tribological systems, even in adverse lubrication conditions. However, hard coatings usually make the friction coefficient higher, because of their high interfacial shear strength. Amongst hard coatings, diamond-like carbon (DLC) is widely used, because of its relatively low friction and superior wear resistance. In practice, conventional lubricants that are essentially formulated for a steel/steel surface are still used for lubricating machine component surfaces provided with protective coatings, such as DLCs, despite the fact that the surface properties of coatings are quite different from those of steel. It is therefore important that the design of additive molecules and their interaction with coatings should be reconsidered. The main aim of this paper is to discuss the DLC and the additive combination that enable tribofilm formation and effective lubrication of tribological systems.
The performance of solids lubricants was evaluated for different materials, mixed to simple grease at 3 wt. %. The first material was commercial graphite. The second one was a graphitic material having special properties, that under intense load becomes electromagnetic , develops a film like diamond on the surfaces. The third one was Al 2 O 3 and finally It was studi ed a special lubricant, CIL ("Composto Intermetálico Lubrificante"), manufactured in cooperation between author and collaborators from UFSC (Federal University of Santa Catarina). The tests were performed in a four-ball machine and it was studied anti-wear property and EP activity of the solid additives. CIL showed best properties and can be used to increase reliability and decreasing maintenance costs.
Proceedings of the 11th International Conference on Tribology – SERBIATRIB ‘09
Because of their favourable properties composite materials with reinforcements are used in many industries. With the aim to additionaly improve some of their properties, especialy their tribological properties several solid lubricants are used in the process of composite production. Many authors have analysed an influence of different reinforcements on mechanical, thermal and tribological properties of metal matrix composites (MMCs). This paper gives an overview of investigations and possibilities of solid lubricant particles (such as graphite) applying as composite reinforcements mainly for aluminium base omposites that are nowdays common in use in automotive and aeronautics industry. Based on presented experimental results of tribological properties one can find some remarks and conclusions that could be useful for further investigation of solid lubricants applying in MMCs production.
CENTRAL ASIAN JOURNAL OF THEORETICAL & APPLIED SCIENCES, 2022
This article discusses the phenomena occurring in the zone of interaction of surfaces during friction and wear of lubricants in the presence of various liquid and gaseous media, as well as the analysis of the effectiveness of lubrication on surfaces during friction.
Wear, 2009
This paper reports on the results of a tribological study that compared the friction coefficient and wear volume of titanium alloy (Ti6Al4V) and 316L stainless steel samples, with and without DLC films, in contact with humidity, water and oils. Distilled water (DW), and synthetic motor oil (SO) were applied to some of the sample surfaces, while others were left uncoated or coated only with DLC. The DLC films were grown by using a Pulsed DC Plasma Enhanced Chemical Vapor Deposition (PE-CVD) technique. The friction coefficient and wear volume of various sample pairs were studied as a function of applied load with constant sliding speed, using sphere-on-flat configuration in the reciprocating mode. The sphere wear was measured using a very small pin approach, in agreement with the ASTM G99 norm. Also, the film's atomic arrangements and graphitization level before and after tribotests were analyzed by Raman scattering spectroscopy. Tribotests showed that the friction coefficient and the wear depend on boundary lubrication, suggesting that the chemistry of the fluid lubricant is an important parameter to be considered. Results showed that the lowest friction coefficient and no wear were obtained to DLC/DLC pair in contact with synthetic oil. The most significant aspect of our work is that with just one friction surface with DLC film it is possible to obtain a 56% reduction in the friction coefficients and no measurable wear, resulting in a 50% reduction in production cost.
SSRN Electronic Journal, 2018
Friction & wear in dynamic part is the core reason for energy loss in system like Engine, gearbox etc., and this can be controlled by using high performance lubricant. In current years, numerous inventive lubricant and new lubrication techniques have been established to attain healthier lubricity and extensive life in stimulating Tribological applications. This paper reviews latest progress in additives and effect of it on lubrication in applications like, Turbine gear box & Engine. In addition to revising the several orthodox and innovative analysis techniques required during experimental analysis, the paper also have presented Tribological properties of oil blended with additives. The motive of this study is to review modern progress in additives in lubricant for different areas. This review on additives has assembled publications about the research advances in Lubricant blended with Additives. The conclusions and key summaries were also given according to the records collected.
A large part of machines (85–90 %) (Garkunov, 2003) lose their efficiency due to wear of parts, which disrupts their normal interaction, causes additional loading, shocks and vibrations, leads to seizures and jams and to accidents in many cases. This paper presents research methods for tribological properties of restorative and preventive coatings in different lubricating media at sliding friction.
International Journal "Advanced Quality", 2017
Equipment quality and reliability improvement, and reducing environmental pollution trough tribological understanding are of the key challenges facing tribology and especially green tribology today. The paper deals with a question of huge importance in the application of tribology, namely the impact of lubricants and additives on tribological systems characteristics. Consideration is given to the influence of quality improvement of lubricants on the equipment reliability and life extending, as well as on the search for safety solutions to ecological tasks. An illustration of the current development of lubricants and additives is done by the study of the oil-soluble metal-plating composite additive Valena studied in the Tribology Laboratories of the Faculty of Industrial Engineering at the
Chemistry and Technology of Fuels and Oils, 1989
2009
The tribological behavior of composite coating incorporating solid lubricant reservoirs has been investigated in this study. A new method, termed " microbeading" was devised to create microscopic reservoirs on the surface of sputter-deposited hard coatings. Pin-on-disk tests were used to evaluate the lubricating performance of these newly devised composite coatings. Three sizes of the reservoirs were investigated: 1.5, 5 and 10 microm. The 10 microm-sized-reservoirs performed better in terms of reducing friction and extending wear life. These coatings were also evaluated with finite element models. It was found that during ball-coating surface interaction, the lowest stresses and calculated work done were obtained at a critical location at the bottom of hole on the coating with 10 microm holes. Further investigations were conducted using photolithography to fabricate the coatings, which allows a more controlled reservoir distribution on the surface. For these tests, silico...
Tribology International, 2016
Sintered bearings are widely used as machine elements due to their low costs in combination with a stable tribological performance. Given the current and future challenge of global conservation of energy and reliability of mechanically systems, the increase of energy efficiency of sintered bearings would have strong effect due to the tremendous number of mechanical devices. The approach of this investigation is to develop a complete system consisting of a lubricant, which is adapted for an optimized sliding bearing. Friction tests with a rotating ball-on-3-plates tribometer (m$ 0.005) and an application oriented component test (m$ 0.01) show that extremely low friction values can be realized using a liquid-crystalline lubricant in contrast to standard oils.
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