Known as Hardide and originally developed in Russia, the gas phase process is a world first, in that it is the only low temperature, super hard coating technology to be able to coat "out of sight" surfaces and complex shapes uniformly, while at the same time providing a 'self-lubricating' finish that is homogeneous, solid and virtually pore-free. The coating - with a thickness that can be varied for individual requirements - also allows for facilitated finishing.
Hardide, the composition of which is based on tungsten carbide, is also able to challenge all existing coating methods such as PVD, thermal or plasma spraying due to a unique combination of credentials including a hardness of up to 3,500 HV that out-performs spray coatings, hard chromium, nitriding and cementation by a ratio of three to one.
It has a porosity of less than 0.4% and an ultralow-dry friction coefficient (from 0.1 to 0.2) that offers enhanced lubricating capabilities while providing chemical and corrosion resistance to water, salt and acids, plus a wear factor of between 40 and 100 times less than case hardened steel - and up to 10 times less than cemented carbide hardmetal.
Another feature of the Hardide coating, which can be varied for best results between five to 50 microns, is the outstanding erosion resistance that has been shown to outperform steel by a factor of 10 when subjected to water/sand jet tests at a speed of 10 m/sec, and by 100 when the speed is increased to 20 or 30 m/sec.
The Hardide technology produces a family of more than 20 coatings offering a variety of parameters to meet specific application requirements. All these coatings can be produced at one plant, while the composition and structure of each is controlled by process conditions.
Where factors have previously dictated the use of costly hardmetal (also called cemented carbide) or special case hardened steel, these can now make way for coated steel, which is easy to machine and costs less.
One benefit of Hardide is that during the coating process it fills and closes micro cracks and restores the shape and size of worn parts, while the smooth nodular texture ensures quality finishing results. This technology, which has the potential to replace most traditional coating methods including heat treating, has an immediate benefit for internal die tools as it eliminates traditional problems such as droplets sticking to the extrusion die and scratching the extrusion section surface.
Hardide's non-porous coating can also facilitate the release of any molded product in that it has non-stick characteristics. It is also inert and so does not interact with other materials.
Accelerated wear tests showed that five pairs of piston sleeve hydraulic parts coated with 30 microns of Hardide outperformed case-hardened piston sleeves by a factor of seven when subjected to the rigors of oil with diamond abrasive grit. Other more common abrasives like sand would make the difference much more significant.
With the potential to dramatically reduce manufacturing and maintenance costs - Hardide coated parts can last up to 100 times longer - the process offers a major new technological weapon for industrial companies fighting cheap imports from China, Latin America and the Pacific Rim.
Hardide has the potential to provide major benefits for coating companies serving all industry sectors, with specific areas already pinpointed including automotive, aviation, construction and agricultural equipment.
In the automotive sector, the fact that Hardide provides a slippery low friction surface without lubrication will make it attractive to crankshaft bearing manufacturers among others. Its extreme wearability makes it ideal for components such as gudgeon pins and precision parts such as those found in fuel injection systems where there are very strict tolerance issues.
Power steering boxes and suspension components are others in a list of potential applications in the automotive arena. The technology, in theory at least, may even pave the way for a new look at ceramic engines which have previously failed to make the grade because of brittleness limitations.
Areas where Hardide will play a significant role have already been identified as providing a superior coating option for undercarriages, and the internal surfaces of fuel valves can be given the super hard treatment, while hydraulic systems - including actuators - can be made smaller and lighter but will produce a greater performance due to the extra strength.
The Hardide technology also scores heavily over hard chrome coating traditionally used in the manufacture of construction and agricultural equipment. Not only is the Hardide process environmentally friendly (chrome salts solution is so dangerous it is due to be restricted in Europe), it also offers a coating that is three to four times harder and has a much higher resistance to corrosion and aggressive media such as dust and abrasive sand. These are a constant problem for machinery in the agricultural and construction industries.
Tests undertaken by Cronks of Moscow, a Russian and Dutch joint supply venture for road machinery and spare parts, showed it came out on top when used to coat hydraulic systems for forklift trucks.
Meanwhile, the Hardide coating on the internal working surfaces of dies greatly extends their durability (four to five fold greater than that of cemented carbide dies). The reduced friction coefficient enhances the quality of the wire surfaces a factor that will appeal to companies who are using standard dies made of hard materials that are expensive and have a limited operational life.
Hardide's composition, structure, coating method and applications have been protected by international patents covering 67 countries including the United States and Canada, the EU, Japan, Korea, Brazil and Mexico.
It has taken 20 years for Hardide to come to the coatings market after being researched and developed, initially in Russia and more recently in Oxford, England, where the first application development center in the West and only the second in the world - the other being in Moscow -has just been unveiled and from where samples can be obtained on request.
Heading up the team at the new United Kingdom center of excellence are two leading Russian scientists. Professor Yuri Lakhotkin, technical director of Hardide Ltd., is one of the world's leading authorities on chemical vapor deposition used in the Hardide process; while Dr. Yuri Zhuk, Hardide Ltd.'s managing director, is not only a renowned academic but an expert in international technology transfer - and a prime mover in bringing Hardide's benefits to the West.
"What we have with Hardide is not another coating but a solution to problems not solved by existing materials," says Graeme Hitchen, business development manager. "We are looking for suitable partners among the coating industry worldwide to ensure that Hardide achieves its global potential."
For more information on wear-resistant coating, contact Hardide Ltd., phone 44 (0) 1865-309677; e-mail info@Hardide.com; or visit www.Hardide.com.
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