HVAFvs HVOF Coating Technology Comparison

  • The whole point of “versus” gets eliminated by choosing the good characteristic from both the breakthrough technologies and giving more inputs on customer wear problem to give optimum solutions rather than suggesting an expensive affair.
  • “Form follows function” approach wins in all extreme conditions.

HVOF vs HVAF Process Representation Chart Format

Parameter HVOF HVAF
Fuel Kerosene, Gas Gas
Oxidant Oxygen Compressed Air
Combustion chamber temperature, °C 2500-3200 1800-2000
Spray Rate, kg/h 4-5 15-30
Oxide contents in the coating 0,1-0,5% 0,01-0,1%
Hardness of TC Coating 1050-1400 HV 1050-1600 HV
Ductility Moderate High
Metal vaporisation in process Yes No
  • HVAF|HVOF Convertible equipment / technology lets us define coating quality/ cost ratio before we start the process.
    WC-10Co-4Cr Coating Features Coating Hardness, HV300 Coating Porosity, % Deposition Efficiency, Rolls OD 350+ mm, % Young’s Modulus
    Good HVOF 1,050-1,250 <0.8 45-50 300
    HVAF Economy (E) 1,050-1,250 <0.8 65+ 400
    HVAF Balanced (B) 1,250-1,450 <0.5 48 – 58 450
    HVAF Ultra (U) 1,450-1,700 <0.1 36 – 42 450
  • HVAF equipment uses the energy of gas combustion in air to spray metal alloy and carbide.
  • the combustion temperature in anHVAF gun is typically 1000˚c cooler than that in anHVOF coating system.
HVOF coating system

The Adiabatic Combustion Temperature of Fuels in Oxygen and Air (a=1, 20°C, 1 Bar)

  • This lower tempe¬rature is ideal for the gradual heating of the feedstock particles of metals and cemented carbides to or slightly above the metal’s melting temperature.
  • The initial oxygen content in the combustion gas mixture is 5-fold lower in our HVAF process compared to any HVOF coating process.
  • Both factors prevent the oxidation of metals and the decomposition of carbides.
oxidation process
oxidation process

The Kermetico HVAF Gun Schematics

  • The ceramic catalytic insert is used in the combustion chamber to provide stable combustion.
  • The material’s acceleration occurs in the nozzle that has a large diameter.
  • The large diameter of the nozzle ensures that the particles do not interact with the nozzle walls, allowing the use of the longer nozzles for feedstock acceleration, typically from 800 to over 1,000 m/s (2,600-3,300 ft./sec.)
  • The quality and efficiency the Kermetico HVAF process is the result of the relatively low combustion temperature of an air-fuel mixture combined with the axial injection of the feedstock through the wide combus¬tion chamber, where the low gas velocity provides sufficient time for the gentle heating of the powder particles.
  • These factors allow the retention of the original ductility of the powder feedstock in the applied coating, even when the hardness of the cemented carbide coating exceeds 1,600 HV300.
HVAF gun process

Phase Diagram of WCCoCr Powder and the HVAF-Sprayed Coating.

The result is higher hardness, higher ductility, higher corrosion, erosion and cavitation resistance of Kermetico HVAF coatings.

Discover the benefits of the new HVAF Coatings

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