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Work efficiency of friction units in wide temperature range, especially when pressure is changed from atmospheric to deep vacuum, often is not supplyed by oil materials, as decomposition temperature of used in present time lubricating materials does not exceed 250...300 С. When liquid and plastic lubricating materials can be used, working temperature in vacuum turns out to be more low (bad heat sink, decomposition process is attended by evaporation).
Plastic greases application in vacuum is practically not possible.
As a result of sharp changes of the rheological properties, plastic greases turn out to be of little use even with cryogenic temperature. In terms of imponderability, liquid and plastic materials also can not provide normal friction unit work, as they are not able to flow to the friction places or on the contrary with good wettability are spread on the friction surface. When speed of sliding is low, when hydrodynamic greasing is difficult-to-accomplish, especially with exploitation of friction units in conditions of high temperature, usual lubricating materials also become of little use.
SLC does not have defects of plastic and
liquid lubricants in extreme conditions of work.
All this is has determine the development necessity of the new direction in lubricating technique - creation of principally new form of the lubricating materials - solid lubricating materials (SLC), in most cases lacking defects peculiar to liquid and plastic lubricating materials.
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Main distinction of solid lubricating compositions (SLC) from usual plastic greases and oil consists in fact, that they are integral part of friction unit. SLC should be strongly set aside of rubbing surfaces and provide full resource of product work during non-permanent laying.
Historically graphite is first material, which
has been served as base for SLC.
Crystalline graphite grate.
Solid lubricating compositions on the graphite and molybdenum disulfide base are used from 40-th of the XX century. Initially they have had limited area application, which has been combined with cosmic technique and military industry mainly because of high price on the raw materials.
Initially SLC have been used only in military and cosmic technique.
Historically, laminated hard materials have been used as solid lubricants but from the beginning of 60th, together with development of polymeric chemistry, has appeared steady tendency to use as solid lubricants multicomponent compositions on the base of synthetic resin (polymeric materials) and antifriction stuff.
SLC are used for decreasing the friction and wear coefficient between rolling and sliding surfaces in various friction units. During work such antifriction coatings provide gradual burn-in of the wear faces. At the same time polymeric coupling agent causes durable adhesion of lubricating material to the metal. As a result of dominant, wear of anti friction covering, the strong detail surface wear during contact "metal-metal" is prevented.
Basic requirements of SLC are low friction coefficient, high wearing capacity, then - durability of the covering, plating simplicity.
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