Solid lubrication mechanism

Kanakia, M.D. and Peterson, M.B., Literature Review of Solid Lubrication Mechanisms, Interim Report BFLRF No. 213, US Army Belvoir Research Development and Engineering Center, November, 1986. (AD A185010). 

Figure 19.1 Schematic of solid lubrication mechanism. Reproduced with permission from Ref [3].

Calcium complex soap greases, obtained by the reaction of lime and a mixture of fatty acids and acetic acid. These greases offer good high temperature and anti-wear/extreme pressure properties related to the presence, in the soap, of calcium acetate that acts as solid lubricant they have good mechanical stability. 

UHMWPE possesses a unique combination of mechanical and technological properties and enjoys a variety of special applications based on low friction (solid lubricant), wear resistance (protection of metal surfaces), excellent chemical stability, as well as radiation and neutron resistance. UHMWPE is used in chemical processing, food and beverage industries, foundries, the lumber industry the electrical industry, as medical implants and in mining and mineral processing sewage treatment, and transportation. 

The most likely application of the chalcogenide nanotubes is as solid lubricants. Mo and W chalcogenides are widely used as solid lubricants. It has been observed that the hollow nanoparticles of WS2 show better tribological properties and act as a better lubricant compared to the bulk phase in every respect (friction, wear and life-time of the lubricant).142 Tribological properties of 2H-MoS2 and WS2 powder can be attributed to the weak van der Waals forces between the layers which allow easy shear of the films with respect to each other. The mechanism in the WS2 nanostructures is somewhat different and the better tribological properties may arise from the rolling friction allowed by the round shape of the nanostructures. 

Janes, Neumann and Sethna ° reviewed the general subject of solid lubricant composites in polymers and metals. They pointed out that the reduction in mechanical properties with higher concentrations of solid lubricant can be offset by the use of fibre reinforcement. Glass fibre is probably the most commonly used reinforcing fibre, with carbon fibre as a second choice. Metal and ceramic fibres have been used experimentally to reinforce polymers, but have not apparently been used commercially. To some extent powders such as bronze, lead, silica, alumina, titanium oxide or calcium carbonate can be used to improve compressive modulus, hardness and wear rate. 

The factors involved in choosing the best solid lubricant for a particular application are complex. Where the application is in an important mechanical system, it will be necessary to study the properties and performance of the various candidate materials In detail, and then to carry out realistic evaluations to ensure that the chosen material is suitable. 

Puchkov, V.N. and Pashkov, A.I., Determination of the Shear Resistance of Solid Lubricant Coatings, Mechanical Sciences, 2, 44, (1974). 

Finkin, E.F., Mechanical Aspects of Solid Lubricant and Elastomeric Coatings, Science and Technology of Surface Coatings, Academic Press, London, 1974. 

Tsuya, Y., Microstructure of Wear, Friction and Solid Lubrication, Technical Report No. 81 of Mechanical Engineering Laboratory, Tokyo, 1975. 

Gamulya, G.D., Dobroval skaya, G.V., Lebedeva, I.L. and Yukhno, T.P., Orientation of MoSj Particles on the Frictional Surface of a Solid Lubricant Coating, Mechanical Sciences, No. 6, 67, (1978). 

Bartz, W.J. and Xu, Jinfen, Wear Behaviour and Failure Mechanism of Bonded Solid Lubricants, Lubric. Eng., 43, 514, (1987). 

Fusaro, R.L., A Comparison of the Lubricating Mechanisms of Graphite Fluoride and Molybdenum Disulfide Films, Proc. 2nd Inti. Conf. on Solid Lubrication, (15 -18 August 1978), ASLE SP-6, p. 59. 

Fleischauer, P.D., Hilton, M.R. and Bauer, R., Effects of Microstructure and Adhesion on Performance of Sputter-Deposited MoSj Solid Lubricant Coatings, in Mechanics of Coatings, (Dowson, D., Taylor, C.M. and Godet, M., eds.), Elsevier Tribology Series 17, Amsterdam, 1990. 

Anderson, M.J. and Roberts, E.W., An Assessment of Solid Lubricant Films for Use in High Temperature Space Applications, Proc. 5th European Space Mechanisms and Tribology Symp., ESTEC, Noordwijk, Holland, (28-30 Oct. 1992). (ESA SP-334, Apr. 1993, p. 379). 

Wu, Y., Wang, F., Cheng, Y. and Chen, N., A Study of the Optimization Mechanism of Solid Lubricant Concentration in Ni/MoSj Self-Lubricating Composite, Wear, 205, 64, (1997),... 

Holinski, R., Lubrication Mechanism of Solid Lubricants in Oils, ASLE Trans., 18, 263, (1975). 

Campbell, M.E., Solid Lubrication Technology a Review, Mechanical Engineering, 90, 28, 1968. 

Figure 6.1 has been reproduced from the Proceedings of the Institution of Mechanical Engineers, Lubrication in Hostile Environments titled Influence of the Atmosphere on the Endurance of Some Solid Lubricants Compared at Constant Layer Thickness by A W J de Gee, A Begelinger and G Salomon 1968-69 Figure 3.3 page 21 by permission of the Council of the Institution of Mechanical Engineers. 

Porosity of Ceramics, Roy W. Rice Intermetallic and Ceramic Coatings, edited by Narendra B. Dahotre and T. S. Sudarshan Adhesion Promotion Techniques Technological Applications, edited by K. L. Mittal and A. Pizzi Impurities in Engineering Materials Impact, Reliability, and Control, edited by Clyde L. Briant Ferroelectric Devices, Kenji Uchino Mechanical Properties of Ceramics and Composites Grain and Particle Effects, Roy W. Rice Solid Lubrication Fundamentals and Applications, Kazuhisa Miyoshi... 

Extrinsic lubrication is provided via mechanisms that apply a lubricating substance, normally paraffin oil, to the tableting tool surface during processing. One method makes use of an oiled felt washer attached to the lower punch below the tip. This washer wipes the die cavity with each tablet ejection. To avoid having tablets stick to the punch faces, materials such as poly-tetrafiuorethylene or polyurethane have been applied to the faces. Another lubrication method sprays a thin layer of lubricant (either liquid or solid lubricant) onto the tool surfaces after one tablet is ejected and before the granulate of the next tablet enters the die cavity. 

The most important factor governing the tribochemical reactions under boundary friction is associated with the action of exoelectrons with lubricating oil components [21]. This is the basis of negative ion-radical action mechanisms, NIRAM. The general model of NIRAM assumes creation of two types of activated sites on friction surfaces, i.e. thermally activated sites and sites activated by exoelectron emission, FEE processes, Fig. 8.4. Comparison with thermally stressed solids and mechanically treated solids shows reactivity is often increased by several orders of magnitude, particularly in the low-temperature range. 

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