In the High Velocity Oxy Fuel (HVOF) process, powder is introduced axially into a chamber in which a gas flame is constantly burning under high pressure. The exhaust gas exits through an expansion nozzle which produces a high velocity gas stream. The powder particles are heated in this gas stream and transferred by it with kinetic energy to the surface of the work piece, forming a dense coating with excellent bonding properties.
Due to the moderate transfer of heat to the powder particles and to the work piece, which remains relatively cool, there is little metallurgical change to either the sprayed material or work piece.
Advantages:
- Very Dense Coatings
- Excellent Bonding
- Minimal Metallurgical Changes
- Minimal Temperature Effects
High Velocity Oxygen (Gas) Fuel
Depending upon your requirements, propylene, propane, hydrogen, or natural gas may be used as the fuel in our High Velocity Oxygen (gas) Fuel (HVOF) thermal spray systems. As a result of the high kinetic energy transferred to the particles through both HVOF processes, the coating material generally does not need to be fully melted. Instead, the powder particles are in a molten state and flatten plastically as they impact the workpiece surface. The resulting coating has a very predictable chemistry that is homogeneous and has a fine granular structure.
Process basics
| Heat source | Fuel (gas) and Oxygen |
| Material | Powder (Metal) |
| Flame temperature | Approx. 2,800 °C |
| Particle velocity | 400 – 800 m/s |
| Spray performance | 40 – 150 g/min |
Key characteristics
- Produces coatings that are very clean, hard, and dense with fine, homogeneous structures
- Coatings are tenaciously bonded to the substrate
- Has low compressive stress, which results in very thick coatings
High Velocity Oxygen (Liquid) Fuel
For High Velocity Oxygen (liquid) Fuel (HVOF) spraying, we use an oxygen-kerosene mixture. We axially feed the coating material, in powdered form, through the gun, generally using nitrogen as a carrier gas. The fuel is thoroughly mixed with oxygen within the gun and the mixture is then ejected from a nozzle and ignited outside the gun. The ignited gasses surround and uniformly heat the powdered spray material as it exits the gun and is propelled onto the workpiece surface.
Process basics
| Heat source | Fuel (liquid) and Oxygen |
| Material | Powder (Metal) |
| Flame temperature | Approx. 2,800 °C |
| Particle velocity | 400 – 800 m/s |
| Spray performance | 70 – 200 g/min |
Key characteristics
- Produces coatings that are very clean, hard, and dense with fine, homogeneous structures
- Coatings are tenaciously bonded to the substrate
- Has low compressive stress, which results in very thick coatings
