Benefits of Dry Film Lubrication: -
Dry Film Lubrication
Coatings designed for Low Friction and Dry Lubrication provide permanent lubrication with consistent low friction performance over the wear life of the coating. Correct coating selection coupled to appropriate bearing design ensures low friction for the life of the mechanism or machine. There are many examples which can vary from an edge cutting tool used for tough materials, to a pedal shaft on a car where squeaks must be eliminated for life coupled with ease of actuation or a seat belt locking mechanism which must release every time despite the load applied.
The Indestructible range of Low Friction Coatings incorporates blends of solid lubricant bonded permanently to a substrate. The selection of the correct coating take account of the bearing abrasive condition, the smoothness of the mating surface, the pressure or load and the relative speed of the two surfaces. These factors are all vital to a successful bearing which should ensure the lowest possible friction and consistent lubrication for the duration of the design life of any bearing.
When bonded to either metal, plastic substrates, these coatings will extend the lifetime of components whilst eliminating annoying squeaks, chatter, fretting galling or scuffing.
Frictions in a dynamic situation causes heat, wear, and absorb energy. Bearing failure is often caused by overheating and subsequent bearing seizure. The bearing property of a dry lubricant coating has the ability to withstand high temperature without catastrophic failure through sudden melt or breakdown.
Indestructible Low Friction Coatings are based on thermosetting polymers, which withstand a wide temperature range and exceed the operating limits of most conventional mineral and synthetic oils.
Most Indestructible Low Friction Coatings are based on PTFE as the solid lubricant whilst others use MoS2 or Graphite with binder systems to match the prevailing conditions. Polytetrafluoroethylene (PTFE) offers the lowest friction coefficient of any known solid with an equally low static coefficient of friction to dynamic. This unique low static friction ensures that mechanisms, which are required to operate intermittently, function on demand. Such products as fire extinguisher plungers or screw-threaded fasteners with low “break out“ torque
are perfect examples. Low dynamic friction on bolt will also ensure that the design tension in the bolt is achieved from the applied torque without it being dissipated in overcoming thread friction.
Indestructible Paint Limited will ensure the correct selection and application of a coating to give permanent lubrication, low dynamic friction and equally low static friction in a variety of corrosive environments. Advice on the correct choice of coating is part of the Indestructible service.
Dry lubrication suggests low constant friction with permanent protection from damage “pick up”, fretting or bearing seizure under a given load and speed range of two sliding surfaces.
For many applications an Indestructible coating ensures that this will be achieved thus providing the most cost effective solution. Other proprietary systems, some requiring lubricant maintenance programmes, can be complicated and more costly though not necessarily more reliable.
Coatings provide permanent lubrication and protect from corrosion in inaccessible locations or arduous conditions such as high temperatures where oils or greases cannot be used. For example the lubrication of an electric toaster mechanism benefits from the use of a coating on two counts. First it has to work at high temperature and secondly cannot employ any greases due to both the operating temperature and potential contamination of the food.
Apart from low dynamic friction, Indestructible coatings also offer a low static coefficient of friction and release. This ensures the intermittent or occasional operation after long periods of time when not in use. For example, a fire extinguisher actuation mechanism or the moving parts in an air conditioner are required to operate on demand after long periods of inactivity. In these applications, a coating not only guarantees lubrication at the sliding surfaces but also provides protection against any corrosive seizure. The coating of a threaded fastener provides corrosion protection and constant friction to the threads, which enables the design tension to be achieved in each case from a pre set torque-wrench.
It is important that the fastener or nut cannot “back–off”.
By coating one surface of any sliding or potentially moving part, one can ensure that lubrication is retained at any union when otherwise it could fail at some time in the life of the plant or mechanism.
Indestructible Low Friction Coatings can be specified to achieve protection against corrosion whilst providing permanent dry lubrication to moving components. Bearing load and velocity determine the type of coating to be used and systems to protect from certain corrosive conditions can be specified. Taking account of the mating surface and the tolerance within the bearing, wear can be predicted at the design stage pf the component to optimise system reliability throughout its operational life.
Indestructible Low Friction Coatings can be applied inexpensively, easily and to within exacting tolerances to enhance the performance as well as to eliminate any possibility of fretting, squeaking, galling or chatter. Coatings can be applied to virtually any metal substrate and also plastics. In any design a coating can be specified to provide permanent dry lubrication to any area that could be subject to wear. In locations where precise tolerances are necessary, a coating can be applied to within a few microns thickness. In certain cases, coatings can be machined back to even more exacting limits.
An Indestructible low Friction Coating is applied to one of two sliding surfaces. If wear life is to be extended, both surfaces can be coated but there are no advantages in terms of lubricity. For example : To provide dry lubrication to a bearing comprising a shaft and journal, the coating would normally be applied to the shaft for reasons of economy and ease of application. The mating surface of the journal should be within a certain tolerance for the optimum wear rate which in general should be 0.2-0.3 microns rms (8-12 micro-ins). Smoother or rougher surfaces outside this tolerance, would give higher wear rates for the same coating.
Coatings can be used in conjunction with wet lubrication such as on an internal combustion engine piston to prevent wear or “pick up” at the ends of its stroke when the hydrodynamic oil lubrication no longer protects the moving surfaces. Piston skirts in heavy diesels can also be coated to prevent this kind of wear whilst in high performance racing engines; coatings will reduce friction and increase performance.
The application of these coatings is not complicated. They are normally spray coated and heat cured to substrate. Systems are available where lower cure temperatures are needed as with certain plastics. Different surface pre-treatments can also be employed to promote increased wear resistance or higher corrosion protection. Coatings can be either applied on “in house“ O.E.M spray plants or by specialist trade coating companies. These service companies have evolved to provide excellent geographical coverage.
Indestructible Low Friction Coatings are also used for coating small components in bulk, where dip-spin or Quadrant coating techniques are employed. Dip-Spin is used for small fasteners, particularly in the automotive field, where coating has now virtually replaced electro-plating. Quadrant coating is carried out in an automatic bulk spray-coating machine, which provides greater accuracy and flexibility.
Indestructible coated surfaces compare and even out perform proprietary dry bearings at a fraction of the cost. By re-engineering the surface properties in terms of surface friction and release with the addition of corrosion protection to the substrate, the designer is able to specify a dry lubricant bearing surface in locations difficult if not impossible for any proprietary bearing. To coat components at still less cost than the use of a bearing shell but with the advantage of providing overall corrosion protection, is a considerable design advantage.
Indestructible Low Friction Coatings save the cost of specifying exotic metals and materials to withstand corrosive environments. A dry lubricant, low friction or release coating whilst selected primarily for these mechanical properties will also protect the substrate from corrosion or degradation.
Basic metals and plastics selected for strength or resilience is often the most economic and cannot only be maintained in any design but improved by adding surface lubricity. Metals specified for there dimensional stability, toughness or weight, can be protected from corrosion and selectively “surface engineered” to eliminate the need for an extensive design change.
For example, hot-dip galvanising can protect B7 stud Bolts, specified for chemical plant and offshore applications. PTFE based coated bolts, over phosphate or plating, have now largely replaced this demanding market. B7 steel has the tensile strength and properties required for undersea and “splash zone” offshore uses but corrode rapidly in those environments. Galvanising gave good corrosion protection but threads had a tendency to gall making it difficult to achieve the design tensions of the bolt and often impossible to disassemble. Stainless steel, ten times more expensive than a coated bolt was one solution. The coated B7 bolt, however, has proved to be the most economical with the added advantage of a thread lubricated permanently to ensure that the design tensions are achieved with ease of “break out” torque.
Engineered dry lubricant coatings offer a permanent solution to most lubrication problems.
Many materials are used as dry bearings. These range from nylon (polyamide), polyacetal, polyethylene, polyimide, peek and fillers such as Graphite, MoS2, PTFE and combinations all of which are selected for optimum performance at the required load/speed range.
Nothing, however, compares with a PTFE filled system where the binder provides the restraint for the relatively soft filler and prevents the cold flow of the PTFE under load. PTFE systems offer the lowest coefficient of dynamic friction with an equally low static coefficient of friction. The measure of a bearing is determined by the durability and consistency of the dynamic coefficient of friction during the life of the coating. This must be constant and bearing failure will occur when friction increases from that constant.
Indestructible Low friction Coatings provide combinations of solid lubricants including PTFE and other fluoropolymers in a composite coating designed to restrain and release lubricant consistently throughout the wear life.
Solid plastics, used as dry bearings, do not possess the dimensional stability of a coated metal bearing. Moreover, some plastics do not have very high temperature properties, which reduces their bearing capabilities still further. Other plastics can be selected for their high temperature capability but these have poor frictional properties and little inherent lubricity.
Friction generates heat, which can cause bearing failure and seizure. Indestructible Low Friction Coatings offer the lowest possible static and dynamic friction for the load and speed characteristics of the bearing condition combined with the highest temperature resistant thermosetting binder systems available.
In comparing many materials used as dry bearings, composite bearing shells or sheet, an Indestructible Low Friction Coating selected for the load and speed prevailing, not only compares but often out performs at a fraction of the cost of a proprietary bearing,
Please contact our sales office for more information or investigate our Ipslip Range.
Please contact our sales office for more information.
