Solid lubrication in fluid film lubrication

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.

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.

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.

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.

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.

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.