Tungsten Carbide Coating
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Tungsten carbide coating and sprays have increasingly become the most preferred method for improving or salvaging components. Thermal spraying is a process of coating that involves spraying melted materials onto the surface of another component with the aim of coating it. It is the nature of machines to undergo corrosion and wear. Throughout history ways to minimize and ultimately eliminate the effect of friction and other physical elements, has been researched with no success often because it is impractical. For many years, several techniques have been developed to curb the wear and corrosion of industrial gear with each being an improvement of the previous one. From polishing to electroplating in the 1850s, chrome plating and finally thermal spraying. The later has proven to be the most efficient and reliable and with a few improvements over the years, has become the most superior.
Tungsten Carbide Powder
Coating materials are always often available in powder or wire form and made from metal, plastics alloys or composites. These substances are then heated by an electrical arc, plasma or by mechanical means to a molten state and are then discharged onto a surface. The coat depth can vary from about 25 micrometers to a few millimeters.
The success or quality of the coat is measured in the form of its bond strength, general and micro hardness, oxygen content, porosity among other physical parameters. This present day cutting-edge technology employ the use of tungsten carbide (WC) to produce the best and the most scratch and corrosion resistant coats in this day. To understand why, here are a few properties tungsten carbide possesses that make it a cut above the rest. Tungsten carbide is known to be twice as stiff as steel with a remarkable young’s modulus of 640 Gpa. This makes it denser than titanium. It exists in fine gray powder, and its common uses include, industrial machinery, armor piercing high-velocity rounds, and cutting tools placing it on top of the list of substances suitable for protective coating.
Tungsten carbide coating is done through a process known as High-Velocity Oxygen Fuel spraying (HVOF). This tungsten carbide coating process involves the use of combustive thermal spray at high velocity to develop exceptional wear and corrosion resistance. It is by far the most preferred method of coating owing to the many benefits it presents. Besides bringing better adhesion to substrates, High-Velocity Oxygen fuel coating delivers a better toughness coefficient and remarkable wear resistance. Its high temperature ensures extremely low porosity that goes a long way in providing impressive resistance to corrosion. The high velocity and temperature combine heat and pressure to provide a clean and smooth coating finish, hard to come by through other coating methods. Unlike other forms of coating, tungsten coating does not require special conditions. It can, therefore, be performed in virtually any industrial setting or workshop.
Different HVOF guns employ varying means to achieve high-velocity thermal spraying, the most common method being basically a high-pressure water-cooled HVOF incineration cavity and long nozzle. Here, the use fuel such as, acetylene, hydrogen or kerosene and oxygen are injected into the chamber with combustion producing a hot, high-pressure flame that is then funneled into a nozzle and as result, increasing its velocity. In this method, the powder may also be fed into the HVOF ignition chamber when under very intense pressure or even injected into the side of the nozzle where the force of the substrate is significantly lower. However, there is another technique that utilizes a simpler system. It makes use of an air cap and a high-pressure combustion nozzle. The fuel gas (hydrogen or propane) and oxygen are delivered at great pressure, combustion then occurs outside the gun’s nozzle, within an air-cap that has been supplied with the compressed air. The high pressure air squeezes and quickens the flame and acting coolant for the HVOF-gun. The powder is then added at high pressure from the center of the gun’s nozzle. The molten particles, often under very high pressure, strike the substrate surface possessing high kinetic energy and often do not need to be completely molten to form high-quality coatings synonymous with HVOF processes. This is without doubt advantageous for carbide-cermet type coatings. This is among the common areas in which where this process performs exceptionally well. Coatings produced through HVOF Processes are generally very strong and dense and often exhibit a superbly reduced residual tensile stress and stress. This unique feature certainly enables thicker coatings to be used than was previously possible with all the other processes. A remarkable new improvement.
These coatings can, therefore, be utilized in any applications that require the highest strength and density not commonly found in most of the other thermal spray treatments. As a result, more new applications that were previously not appropriate for this type of coating are becoming increasingly viable. HVOF, though a subset of flame spray has two basic and distinct differences with the conventional flame spray. First, this type of spraying utilizes confined combustion and a cleverly extended nozzle that heat and accelerate the powdered coating material, in this case, tungsten carbide. Typically, these devices operate at very high velocities usually greater than MACH 5 (5 times the speed of sound). At these extreme speeds, tungsten carbide provides kinetic energy that then helps produce coatings that are dense and very well adhered or stuck. A number of industries and mechanical workshops that initially preferred other means of surface treatment are now increasingly using thermal sprays to protect and proof their systems against attack by wear or corrosion agents. This has subsequently inspired improvements and the present thermal spray system is nothing short of engineering perfection.
These differences are quite significant as are mark the superiority of HVOF to the traditional flame spray. Typical applications for tungsten carbide powder for tungsten carbide coating include; gate valves, stems, actuators, drive shafts, actuators, stabilizers, enclosures and hydraulic rams. This basically sums up all the heavy machinery industry. Tungsten carbide coating is, therefore, one the most influential pieces of technology and one who’s significant cannot be overstated. It breaks all the thermal barriers and challenges previously presented before by the technology that came before it. It is a leader in this market and opens up possibilities in the galvanization and coating business that previously not viable. Due to attributes that are formed from tungsten carbide properties, it make it a definite compound that each and every major industry player must explore.
National Alloy Solutions stocks and sells a wide variety of high-quality custom engineered HAI thermal spray powders and cold spray powders. These materials are ready-to-ship for all your coating applications.
We offer a wide range of HAI MCrAlYs, metal alloys, carbides, ceramic oxides, and precious metals along with custom engineered, APT and proprietary HAI powders for your most demanding markets. NAS also stocks and sells our own Chromium Carbide and Tungsten carbide based HVOF powders. Contact for a full list of powder inventory.