Solid Lubrication

Note that for certain older engines, small quantities lead deposits from combustion could have a positive effect as a solid lubricant and prevent exhaust valve recession. For these motors which still represented in 1993 from 20 to 30% of the French automotive fleet, the use of unleaded fuel is not possible. 

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. 

The role of anti-wear and extreme-pressure additives is to create a solid lubricant at the interface of the metal by chemical reaction. 

The growth of solid films onto solid substrates allows for the production of artificial stmctures that can be used for many purposes. For example, film growth is used to create pn junctions and metal-semiconductor contacts during semiconductor manufacture, and to produce catalytic surfaces with properties that are not found in any single material. Lubrication can be applied to solid surfaces by the appropriate growth of a solid lubricating film. Film growth is also... 

Sokd-liquid separations Solid lubricants Solid modeling... 

A variety of chemical additives can be incorporated in lubricating oils to improve their properties under boundary lubrication conditions. Some of these additives react with the surfaces to produce an extremely thin layer of solid lubricant, which helps to separate the surfaces and prevent seizure. Others improve the resistance of the oil film to the effect of pressure. 

Bearings in space vehicles operating in vacuum with fluid or solid lubricant (TiC). 

Hintermann, H., Coatings and Solid Lubricant Films for Extreme Conditions, in Engineering Ceramics, pp. 54-59, Sterling Publications, London (1988)... 

The expectation of the structural dependence of lubrication motivated great numbers of investigations that intended to prepare and use highly ordered organic films, such as the Langmuir-Blodgett (L-B) hlms and Self-Assembled Monolayers (SAMs), as solid lubricant, which will be discussed more specihcally in Section 4. 

Finally, there is another category of lubricants, including the laminated materials, highly ordered organic mono-layers, and various thin solid hlms, which provides effective lubrication via their properties of low shear strength or high wear resistance. Lubrication via ordered molecular films and other solid lubricants, which have been considered by some investigators as a sub-discipline of boundary lubrication, will be discussed more specifically in Section 4. 

The most commonly used amphiphiles to build L-B hlms for tribological applications are the straight chain hydrocarbon compounds with simple functional groups such as the fatty acids, including stearic acids, arachidic acids, and behenic acids [32], but other amphiphilic molecules, e.g., 2,4-heneicosanedione and 2-docosylamina-5-nitropyridine, are also applied in some cases. There are two major systems of self-assembled monolayers, namely the alkylsilance derivatives (e.g., OTS, octadecyltrichlorosilane) on hydroxylated surfaces and the alkanethiols on metal substrates, which have been investigated extensively to examine their properties as solid lubricants and protective surface films [31 ]. 

Molybdenum disulhde (M0S2), graphite, hexagonal boron nitride, and boric acid are examples of lamella materials commonly applied as solid lubricants. The self-lubricating nature of the materials results from the lamella crystalline structure that can shear easily to provide low friction. Some of these materials used to be added to oils and greases in powder forms to enhance their lubricity. Attention has been shifted in recent years to the production and use of nanosize particles of M0S2, WS2, and graphite to be dispersed in liquid lubricants, which yields substantial decreases in friction and wear. 

Soft metals such as In, Ag, Sn, Pb, and Au can lead to reasonably low friction coefficients, when used as solid lubricants, due to their low shear strength. The metals were generally applied as thin films prepared by the vacuum deposition process. Especially, in applications to the high temperature conditions where liquid lubricants fail due to the evaporation, the thin films of soft metals can provide effective protection to the surfaces in sliding. 

Miyake, S., Sekine, Y., Noshiro, J., and Watanabe, S., Low-Friction and Long-Life Solid Lubricant Films Structured of Nanoperiod Tungsten Disulfide and Molybdenum Disulfide Multilayer, Jpn. J. Appl. Rhys., Vol. 43, 2004, pp. 4338-4343. 

Several oxides and sulfides display the characteristics of network solids. The bond network of silica appears in Section 9-. Other examples are titania (Ti02) and alumina (AI2 O3). These two substances have extremely high melting points because their atoms are held together by networks of strong a covalent bonds. Like graphite, M0S2 is a two-dimensional network solid that serves as a solid lubricant. 

Laboratory experiments have been conducted with a chromium lignite-chromium lignosulfonate mud system both without and with solid lubricants. These studies include filtration loss, cake quality, and their impact on the formation. A comparative evaluation has led to the conclusion that Gilsonite is a better additive compared with sulfonated asphalt as it results in less filtration... 

V. Garg, M. Ralhan, H. C. Tewari, A. Srivastava, S. K. Nanda, and H. S. Rawat. Impact assessment of solid lubricants used in drilling fluids on the producing zone. In Proceedings Volume, volume 3, pages 55-60. 1st India Oil Natur Gas Corp Ltd et al Int Petrol Conf (Petrotech 95) (New Delhi, India, 1/9-1/12), 1995. 

Liquid paraffins, particularly those of low viscosity, have been used and are said to be of value for colored tablets, and even the use of modified vegetables has been attempted. However, they appear, in general, to offer little advantage over solid lubricants, and their incorporation into the precompression mixture is more difficult, requiring solution in a volatile liquid that is then sprayed onto the unlubricated material. Due to handling and EPA requirements, these materials are often rejected in the preformulation stage. 

The extrusion process requires the use of a lubricant to prevent adhesion of the aluminum to the die and ingot container walls. In hot extrusion, limited amounts of lubricant are applied to the ram and die face or to the billet ends. For cold extrusion, the container walls, billet surfaces, and die orifice must be lubricated with a thin film of viscous or solid lubricant. The lubricant most commonly used in extrusion is graphite in an oil or water base. A less common technique, spraying liquid nitrogen on the billet prior to extrusion, is also used. The nitrogen vaporizes during the extrusion process and acts as a lubricant. 

Kokkoris et al. (1991, 1995) suggested another method to impair catalyst attrition. In a small scale slugging bed they reduced the attrition rate of zeolites by addition of only very small quantities of various fine solid lubricants. In the case of graphite the reduction was up to 30%. The fines were assumed to reduce attrition by forming a protective coating that... 

Kokkoris, A., and Turton, R., The Reduction of Attrition in Fluidized Beds by the Addition of Solid Lubricants, AIChE Symp. Ser., 281(87) 20 (1991)... 

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