Tungsten Carbide Coatings: Applied by the High Velocity Thermal Spray Processes
At ASB Industries, tungsten carbide coatings are the most frequently-applied wear resistant surface treatments. Using an array of HVOF systems allows us to choose the best powdered feedstock for your application, enabling consistent production. Our spray rooms are designed to accommodate a wide range of components, utilizing large turning capabilities and equipment ranging from robots and X-Y gun manipulators to overhead cranes. Specialty-built fixtures are used to handle repetitive production; complex masking fixtures protect uncoated areas.
HVOF Thermal Spray
In the continuous-combustion HVOF (High Velocity Oxygen Fuel) thermal spray process, a fuel gas and oxygen are combusted in a high-pressure chamber reaching temperatures from 4500° to 5600°F. The resulting hot, high-pressure gas is ejected through a small-diameter nozzle and accelerated down a long barrel at supersonic speeds. Powder, such as tungsten carbide, is also injected into the nozzle, where the particles mix with the speeding gases, reaching velocities up to 3000 ft/s.
These high speeds impart tremendous amounts of kinetic energy into the powder particles. When these highly energetic particles strike the substrate, their velocity drops to zero and they absorb their kinetic energy, which causes them to bond instantly. Subsequent particles arrive almost simultaneously, rapidly building up the coating. This results in very dense, very adhesive and cohesive tungsten carbide coatings, with comparatively very high bond strength, low residual stress, low porosity (typically less than 0.5%), and high wear resistance.
Specialized Tungsten Carbide Coatings
To produce our tungsten carbide coatings, we use tungsten carbide powder mixtures with a binder material. Tungsten carbide melts at 5200°F and is extremely hard (Vickers hardness number 2242). Cobalt, on the other hand, has a melting point of 2460°F and a Vickers hardness number of 1043.
Coating properties such as hardness, wear resistance, and strength depend primarily on the grain size and volume fraction of the tungsten carbide particles. Therefore, tungsten carbide coatings can be designed to provide the specific properties needed for an application by controlling the grain size of the tungsten carbide particles and their volume relative to cobalt.
ASB Industries’ on-site and in-house capabilities in paper mills allow us to apply long lasting, grip surface tungsten carbide coatings to roll surfaces used in different paper production processes. Using our flame spray equipment, we adapt our carbide spraying parameters to best accommodate the quality and thickness of the paper being produced.
Erosion, abrasion, and corrosion are considerations when choosing different chemistries and binder materials. Tungsten carbide coatings are typically used for extreme wear conditions.
In steel and metals production, tungsten carbide coatings and tungsten weld coatings are widely used from ore production through finished product. A multitude of accepted applications show dramatically reduced maintenance costs and improved production quality.
In power generation where coal is the fuel source, components must be protected from extreme abrasion under demanding production seasonal schedules. ASB Industries has a wide variety of solutions for mission-critical components.
If your application requires a specific finish, then ASB Industries in most cases will be able to apply your tungsten carbide coatings to varying surfaces finishes or Ra. From large to small components, we will most likely be able to finish your project with our diamond grinding and diamond super finishing equipment.