LUBRICANTSThe functions of a lubricant can be multiple: depending on the particular application in addition to the primary lubricant demand – maximum transfer of forces at minimum friction and wear – very often secondary requirements have to be met like resistance to water and chemicals, compatibility with plastics or food and corrosion protection.
Lubricants can be presented in different physical forms : oils, greases, pastes, dry films, solid lubricants.
OILSAs base for high-performance lubricants, mineral oils, synthetic oils, silicone oils, polyglycols, esters and other synthetic fluids are used. They differ from each other by thermal stability, miscibility, lubricating properties, oxidation resistance, materials compatibility and cost.
Careful selection of the base oil is a specific prerequisite to formulate high-performance oils and has considerable impact on the costs/performances ratio.
The composition of modern oils is such that film forming additives protect the surfaces whenever the liquid film cannot carry the load applied.
GREASESIn case design does not permit lubrication by oil a grease is the most appropriate lubricant. A grease is a thickened oil. The thickener acts like a sponge which releases the liquid under pressure.
The lubricating film of a grease is always thicker than that of the base oil alone!
At first glance the structure of high-performance greases is similar to the one of oils. It is the thickener which makes the difference. The amount of thickener and its chemical nature give the consistency wanted. The consistency is normally measured in NLGI grades
Various combinations of base oils and thickeners are possible and result in different performances according to specific applications.
PASTESThe structure of high-performance pastes is similar to the one of greases. The principal difference is the much higher solid content which is typical for both assembly pastes and threaded connections pastes.
With a high content of solid lubricants dispersed in oil they pastes perform really heavy duty in the lubrication process of tribosystems in the "mixed friction" stage (for hydrodynamic lubrication they are not suitable), when containing thermal extremely stable solid lubricants they separate the matching surfaces of high-loaded and temperature stressed threaded connections.
DRY LUBRICANTSDry lubricants or Anti Friction Coating are solid lubricants incorporated into a resin-like matrix of organic and/or inorganic binders in a solvent base.
For good adhesion the surfaces have to be pretreated. Coating methods are dipping, spraying or brushing. After drying and running-in, the sliding film is resistant to high pressures and extreme temperatures, does not absorb dust and remains reliable for a very long time.
SOLID FILMSSolid lubricants due to their structure and chemical-physical properties are materials that produce sliding and separating films on metal surfaces. These films are such thin that close-tolerances in mechanical engineering needs not to be changed.
Solid lubricants are used alone as dry powder fine particles or in the formulation with other lubricating materials to obtain high performance specialty products. They can be classified in structure-effective, chemically effective and physically effective substances. They prevent extreme wear in the critical stages of boundary and mixed friction.