HVAF – High Velocity Air Fuel process description
HVAF Process Inputs
Carbide or Metal Powder is fed into a Kermetico HVAF thermal spray system. The gun burns the compressed air and fuel gas generating a high-velocity jet of gases. The powder is heated and accelerated in the gun. The powder impacts a work-piece (substrate) to form a coating.
Kermetico HVAF systems produce coatings high quality and efficiency is a result of
Powder acceleration occurs in the large diameter nozzle. The large diameter of the nozzle assures that the nozzle walls do not contact powder. No contact reduces the nozzle wear dramatically. That means that Kermetico can design a nozzle that is as long as needed for powder acceleration to over 1,200 meters per second.
HVAF Combo (HVOF / HVAF) costs 1/2 the running cost of the Diamond Jet or JP5000
HVAF vs HVOF
The HVAF process and HVAF coatings are better quality compared to HVOF coatings . The HVAF process is cooler than HVOF by 1,000 C . The air fuel combustion produces much less oxides than high temperature oxygen fuel HVOF.
The HVAF process runs on a fuel gas such as Propane, LPG, or Natural gas (supplied at 140 psi), and compressed air (supplied by a 400 CFM air compressor at 125 psi). There are no additional requirements for water cooling.
|WC/Co/Cr Coating Feature||Typical HVOF||Gun Economy setup|
Gun Balanced setup
|Gun Ultra-quality setup|
|Deposit efficiency, %||40-55%||60-70||48-58||36-42|
|Hardness, HV300||1050-1250 HV300||1050-1250||1350-1450||1500-1700|
|Apparent metallographic porosity||<0.8 percent||<0.8 percent||<0.5 percent||<0.1 percent|
|Bond strength (@0.040” thickness), PSI||+12,000 PSI|
|Range of as-sprayed roughness, µm||3.5-4.5 micron||1-3.2 |
|Maximum coating thickness, mm ||12.7 mm||12.7 mm||3 mm||1.5 mm|
HVAF Coating are better quality than HVOF:
HVAF air-fuel combustion temperature is typically 1000°C lower than in HVOF oxygen-fuel combustion. This lower HVAF temperature is ideal for the gradual heating of the powder to or slightly above the metals’ melting temperature.
The oxygen content in the HVAF combustion gas mixture is 80% lower compared to any HVOF process.
Low Oxygen and lower temperatures prevent the oxidation of metals and the decomposition of carbides and their dissolution into the metal binder. HVAF process retains the original ductility of the powder feedstock material in the final coating. The ductility is kept even when the hardness of the tungsten carbide coating exceeds 1700 HV300.
Kermetico HVAF Benefits
Kermetico HVAF system sprays tungsten carbide HVOF coatings