HVOF (High Velocity Oxy-Fuel) & Carbide Coatings
What is HVOF
High-velocity, oxy-fuel, (HVOF) devices are a subset of flame spray. There are two distinct differences between conventional flame spray and HVOF. HVOF utilizes confined combustion and an extended nozzle to heat and accelerate the powdered coating material. Typical HVOF devices operate at hypersonic gas velocities, i.e. greater than MACH 5. The extreme velocities provide kinetic energy which help produce coatings that are very dense and very well adhered in the as-sprayed condition.
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HVOF is most commonly used to produce very wear resistant coatings such as cermets (ceramic and metal mixes) like tungsten-carbide cobalt, see figure above. Coatings of this type have wear resistance similar to sintered carbide materials. Because HVOF produces very dense coatings (porosity levels typically less than 0.5%), it can be used to produce very good corrosion resistant coatings made from materials such as Inconel®, Stellite®, stainless steel, and ceramics. Some unique coatings produced by TST using HVOF technology are ultra-high density ceramics that provide excellent dielectric strength.
Like most of the thermal spray processes HVOF coatings can be found in several diverse industries. Industries needing wear resistance such as agricultural and construction equipment, food processing, aerospace, etc., HVOF coatings are common. TST also uses the technology for highly sophisticated electronic devices and medical instruments that require high performance dielectric properties.
HVOF coatings can be incorporated into the design of complex components such as high-tech medical devices used for performing complex surgeries, to simple components such as bolts used in agricultural combines. Combines process incredible amounts of crops during harvesting. The wear created by the crop going through the machine can be extreme and in those cases the bolts that are used to attach critical internal components are coated with carbide materials to greatly extend the life of the bolt. The improved bolt assures the component that the bolt is holding remains attached.