High Velocity Oxygen Fuel (HVOF) is the process by which a gaseous or liquid fuel and oxygen are combined within a controlled environment in order to create an energy source that is capable of depositing various Metallic and/or Ceramic surface coatings.
The fuel and oxygen are fed into a combustion chamber, where they are ignited and combusted continuously. The fuels can be gases (hydrogen, methane, propane, propylene, acetylene, natural gas, etc.) or liquids (kerosene, Ethanol etc).
The resultant hot gas expands rapidly and emanates through a converging–diverging nozzle, at a pressure close to 1 MPa. It then continues on through an intermediate, straight section before exiting via the barrel of the chosen Gun or Torch. The jet velocity produced at the exit of the barrel, (>2000 m/s), exceeds the speed of sound. A powder feed stock is injected into the gas stream at various locations, dependant on the chosen Gun or Torch. It is then accelerated up to approx 700 m/s. The jet of hot gas and powder (spray stream) is directed towards the surface to be coated. The powder partially melts in the stream, and deposits upon the substrate. The resulting coating has, among other attributes, very low porosity and high bond strength.
A wide variety of materials can be applied using the HVOF process, in thicknesses ranging between 0.05mm to few mm.
Coatings applied via HVOF process include:
- Ni-/Co-based alloys/Stainless
- (Stellite, Triballoy, Inconel, …)
- Carbides / Cermets
- (WC-Co, Cr2C3-NiCr, …)
Typical applications of the HVOF process:
- (High) Wear resistance
- Sliding, abrasive, erosion, …
- Corrosion resistance (dense)
- Gasses, acids, salt water, …
- HT oxidation / corrosion