HVOF Processes

HVOF Processes

The high temperatures and high velocity present in High-Velocity Oxygen Fuel processes make safety paramount.

Thermach HVOF systems are the perfect mix of safety and performance. Easy-to-use controls, high-impact visual alarms, and a NEMA 12 enclosure provide accurate control over gauge and flow of ceramic and metallic coatings for the optimum corrosion resistance your customers expect.

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How HVOF Spray Works

How HVOF Spray Works

HVOF, High-Velocity Oxygen Fuel, is a process that excels in producing very dense, low porosity, hard-wearing coatings. Unlike other thermal spray processes, where the coating material is melted and sprayed onto the substrate, the HVOF process plasticizes the coating particulate before it hits the substrate. The process works by mixing a fuel gas (commonly hydrogen, propane, or propylene) with oxygen in the torch’s combustion chamber. When the gas mixture is ignited, the combustion gases are accelerated through the nozzle at supersonic speeds, often producing shock diamonds in the exiting flame. The powder is then injected into the gas stream axially or radially, where it softens and gathers speed. Upon impact, the high kinetic energy of the particulate transforms into thermal energy, further aiding in the deformation and interlocking of the particulate with the surface profile. The results are coatings that exhibit density, hardness, and bond strengths that other methods of thermal spray cannot produce.

HV2000 Torch Nomenclature

  1. Spark igniter
  2. Oxygen
  3. Fuel Gas
  4. Powder supply and carrier gas
  5. Water outlet
  6. Water inlet
  7. UV scanner/flame detector

Where HVOF Spray Excels

Tungsten Carbide Sprayed with HV2000 Torch

Where HVOF Spray Excels

HVOF coatings not only produce denser and harder coatings than other thermal spray processes, but they also produce coatings with lower residual stress. Due to lower particle temperatures, the particles spending less time within the heat source, and the peening effect of the high-velocity particles striking the substrate, there is less shrinkage, porosity, and oxidation. These unique properties make HVOF coatings superior at wear resistance and an excellent choice when spraying carbide and cermets.

  • Corrosion resistance
  • High bond strength, > 82 MPa
  • Low compressive stress
  • Minimal porosity, < 1%
  • Very hard coatings, up to 1400 HV
  • Minimal decarbonization
  • Ability to spray carbides (Tungsten carbide coatings are 10x harder than chrome plated)
  • Retention of powder chemistry due to reduced temperature
  • Smoother as-sprayed and ground surface finishes
  • Powder chemistry retention due to the reduced time in heat
  • Lower oxide content because of less particle dwell time

HVOF Applications

HVOF Applications

Thermach thermal spray equipment is a smart, reliable choice for coatings, in the factory and in the field. Here are the applications where High-Velocity Oxygen Fuel (HVOF) Spray is typically used.

  • Agitator Paddles
  • Aircraft Landing Gear
  • Ball Valves
  • Calendar Rolls
  • Compressor Seals
  • Corrosion Protection
  • Crank Shafts
  • Electrical Insulation
  • Gate Valves
  • Hard Chrome Replacement
  • Hard Surfacing
  • Low Friction Surfaces
  • Paper Rolls
  • Pelton Turbines
  • Piston Rods
  • Pump Rotors
  • Repair and restoration
  • Shaft Repair
  • Turbine Blades
  • Turbine Shafts
  • Wear Resistance