HVAF Coating are better quality than HVOF:

Low temperature
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.

Low oxygen

The oxygen content in the HVAF combustion gas mixture is 80% lower compared to any HVOF process.

Ductile Coatings

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.

HVAF – High Velocity Air Fuel process description

HVAF Process Inputs

  • Compressed Air
  • Fuel (propane, propylene, natural gas, etc.)

Carbide or Metal Powder is fed into a Kermetico HVAF thermal spray system. The gun combusts the compressed air and fuel gas generating a high-velocity jet of gases. The powder is heated and accelerated in the jet and, when impacting a work-piece (substrate), forms a coating.

Kermetico HVAF systems produce coatings high quality and efficiency  is a result of

  1. Low combustion temperature of the air-fuel mixture
  2. Axial injection of the feedstock through the long combustion chamber.  In this long combustion chamber the controlled gas velocity provides sufficient time for the powder particles correct heating.

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 C (HVOF and HVAF) is 1/2 the operating cost of Standard HVOF

 Kermetico HVAF Benefits to you

The Kermetico AK HVAF system deposits coatings with

  1. 5-6 times higher spray rate,
  2. 20-30% higher deposition efficiency,
  3. 30% less deviation than any HVOF system.

Definition: High Velocity Air Fuel
HVAF meaning "High Velocity Air Fuel " is a high velocity combustion thermal spray process.  HVAF is used for coatings of tungsten carbide, chrome carbide, metals, and special materials like gold, silver, platinum.

The HVAF process and HVAF coatings are generally comparable (and typically better quality)  to coatings produced by HVOF and Cold Spray. 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 can also apply metals with almost zero oxidation, similar to Cold Spray.

Process Requirements
The HVAF process runs on a fuel gas such as Propane, Propylene, or Natural gas (supplied from cylinders or gas line at 140 psi), and compressed air (supplied by a 400 CFM air compressor at 125 psi). There are no additional requirements for water cooling.

Kermetico HVAF Carbide Coating Process

HVAF Thermal Spray Coatings

HVAF HVOF Process Benefits
WC/Co/Cr Coating Feature
Typical HVOF
Gun Economy setup

Gun Balanced setup

Gun Ultra-quality setup
Deposit efficiency, %
40-55%              60-7048-5836-42
Hardness, HV300
1050-1250 HV300
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
Maximum coating thickness, mm 
12.7 mm12.7 mm3 mm1.5 mm

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