Technologia HVOF/HVAF
HVOF
HVOF: High Velocity Oxygen Fuel
The HVOF process is a thermal spray technology utilizing the kinetic and thermal energy of fuel combustion (kerosene, hydrogen, propane) in oxygen. The gas mixture is accelerated in a de Laval nozzle to supersonic speeds (Mach 3+). Powder particles, injected into the stream, reach speeds of 600-800 m/s and impact the substrate in a plastic state, creating a coating of extraordinary density and mechanical adhesion.
HVAF
HVAF: High Velocity Air Fuel
HVAF technology is an evolution of the HVOF process, where oxygen is replaced by compressed air. This lowers the flame temperature (to approx. 1900°C), preventing carbide decomposition and material oxidation. At the same time, due to the larger gas volume, particles reach even higher velocities (up to 1200 m/s). The result is coatings with zero porosity, higher ductility, and resistance to fatigue cracking.
Technological Advantages
Density & Porosity
Porosity < 1% (often < 0.5%). Tight barrier against corrosion.
Bond Strength
Bond strength > 80 MPa. Coating integral with substrate.
Thickness & Finish
Precise thickness control (50-500 µm). Can be ground to Ra < 0.05 µm.
Materials and Applications
Tungsten Carbides (WC-Co / WC-Co-Cr)
Most popular wear-resistant material. Hardness 1100-1400 HV0.3. Ideal for shafts, piston rods, valves, and drilling tools.
Chromium Carbides (Cr3C2-NiCr)
Wear resistance at high temperatures (up to 850°C) and gas corrosion. Used in power generation (boilers, screen tubes) and aerospace.
Metal Alloys (Inconel, Hastelloy, MCrAlY)
Anti-corrosion and dimensional restoration coatings. Protection against chemical corrosion (acids, bases) and high temperatures.