Tungsten carbide coatings, known for their hardness and resistance to corrosion, high temperatures, and abrasion, are widely used throughout industries such as machinery, metallurgy, oil & gas, and aerospace. For use in other, more general industries throughout the world, protective coatings are formed by the use of raw material tungsten carbide sprayed onto iron-based materials or nickel surfaces.
Before getting into the many ways tungsten carbide coatings can benefit aircraft parts, let’s look at the material itself. Tungsten carbide is a chemical compound containing equal parts tungsten and carbon atoms. In its basic form, tungsten carbide is a fine gray powder, but can be pressed and formed into many shapes for uses in things like industrial machinery, cutting tools, abrasives, jewelry, and armor-piercing projectiles. It is both twice as stiff and twice as dense as steel. The hardness of tungsten carbide is similar to that of corundum, and it can only be polished or finished with abrasives of superior hardness.
Tungsten carbide is made through a reaction of tungsten metal and carbon at 1400-2000°C. It can also be produced by heating tungsten oxide with graphite - either directly at 900°C or submerged in hydrogen at 670°C followed by carburization in argon at 1000°C. Tungsten carbide has many unique physical properties. For one, it has a very high melting point of 2,870°C and a high boiling point of 6,000°C when under standard atmospheric pressure. Despite this, its electrical resistivity is relatively low and is comparable with that of many other metals. The material is wetted, the ability of a liquid to maintain contact with a solid surface, by molten nickel and cobalt.
Oxidation of tungsten carbide begins between 500-600°C, though it is resistant to acids and only vulnerable to mixtures of hydrofluoric and nitric acid above room temperature. It reacts with fluorine gas at room temperature and chlorine above 400 °C, but remains unreactive to dry hydrogen until it reaches its melting point. In terms of its chemical structure, there are two forms of tungsten carbide: a hexagonal form and a cubic high-temperature form with a rock salt structure. The hexagonal form can be visualized as a hexagonal lattice of layers of metal atoms sitting directly over one another, with carbon atoms filling half of the space between them.
Admittedly, implementation of tungsten carbide coatings is expensive. However, compared to the cost of repair or replacement of a damaged component, the savings are significant. In the constantly-evolving aerospace field, surface enhancement coating is a technology that is rapidly growing in popularity. Here, tungsten carbide is among the most important coatings. The constant development of new technology necessitates the development of higher performance requirements, but also brings a myriad of possibilities. Current coating processes include tungsten carbide explosion spraying, tungsten carbide physical vapor deposition, hard chromium plating, and supersonic flame spraying tungsten carbide, to name a few. Although they have their benefits and drawbacks, any of these applications can be considered viable.
Tungsten carbide coatings are most commonly applied using a technique called chemical vapor deposition. Chemical vapor deposition, more commonly known as CVD, is a low temperature coating technique used by many major aviation manufacturers throughout the United States and Europe. Both a technical and practical commercial solution, CVD is a process of tungsten carbide coating depositing. It has been used in three generations of aircraft, but is most commonly used in jet engines where it markedly increases the life expectancy of many different parts.
As cobalt is needed in basic, hard alloy spraying technology, CVD is an extremely popular technique. Thanks to a tungsten carbide material bonding phase, the compactness of a given material can be greatly improved. However, CVD can also result in a reduction of resistance to wear and corrosion. It should be noted that CVD coating is possible with materials other than cobalt. Through the addition of a tight protective layer of tungsten carbide components and tungsten bonded together, even the complex shape of many aircraft components and their inner surfaces can be evenly coated without holes. This is especially helpful for complex geometric shapes and designs that can’t be serviced by ordinary spraying technologies.
There are many more benefits of CVD tungsten carbide, such as the fact that they have no wear quality on anti-body parts including bearings, seals, and others. Even in normally corrosive and abrasive environments, CVD tungsten carbide coating can improve the surface finish and will wear evenly on uniform nanostructures. Furthermore, in bearings, rotating shifts, and hydraulic actuators, a well-coated surface will reduce aircraft actuator and transmission maintenance requirements, help prevent oil from leaking, and reduce the wear of PTFE (Polytetrafluoroethylene) and elastomeric seals. Throughout the aerospace industry, CVD coatings are used on parts and components including flaps, track & plate strips, landing gear, catches, hooks, bearings, bushings, pins, backward thrust rods, and more.
Protecting your aircraft parts with tungsten carbide will not only ensure you can fly safely, but it will also greatly improve the service life of your aircraft as a whole. For aircraft parts of all types and much more, look no further than Aviation Store Online, a trusted supplier of parts for a wide range of industries. We are an online distributor of aircraft parts as well as parts pertaining to the aerospace, civil aviation, defense, electronics, and IT hardware markets. We’re always available and ready to help you find all the parts and equipment you need, 24/7-365. For a quick and competitive quote, call us at +1-714-705-4780 or email us at [email protected]. Our team of dedicated account managers is standing by and will respond to your inquiry in 15 minutes or less, 24/7/365.
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