Thermal Spray
Thermal spraying involves the projection of small softened particles onto a cleaned and prepared surface where they adhere to form a continuous coating. Thermal spraying applied with high kinetic energy causes the particles to flatten or ’splat’ onto the surface, and onto each other, to produce a cohesive coating of successive layers.
Thermal coatings, such as Zinc Coating, Tungsten Carbide coating, Ceramic Spray coatings, PCB coatings or any other thermal spray coating) are very specific in use and require a close and thorough analysis.
Other types of spraying include plasma spraying, wire arc spraying, HVOF, HVAF and cold spraying.
Get in touch with us to find out which application is best suited for your needs.
High Velocity Oxy Fuel (HVOF)
This coating process was invented in the 80’s by Browning & Witfield. The HVOF coating process has been invented on the basis of jet engines. Just as in a jet engine, gasses are mixed and ignited to create a very hot stream of air. In this stream material particles are added and blasted on a surface to create a thin layer of material enhancing greatly the characteristics of the treated part. According to the usage or the characteristic needed the mix of particles can be adapted.
HVOF process
Within the gun used to project the molten material particles in the hvof coating process there are several parts. In the combustion chamber of the gun Oxygen and combustibles (a mix of Hydrogen, Propylene, Propane, Methane, Tetrene or Kerosene) are mixed and ignited. Under the heat (between 2500°C and 3200°C) and the high pressure (0,5 à 0,7 MPa) of the ignition a flow is created.
The second part of the gun mixes the material particles (ceramics, plastics and alloys) is mixed. In direct contact with the particles melt.
The third part of the hvof coating gun consists of a tunnel to increase the speed of the flow even more (300m/s to 360m/s). These particles then are projected on the surface to be treated creating a uniform layer.
There exist 2 types of HVOF spray coating types:
- A low pressure coating process: The gas mixture consists of Oxygen and a gas combustible. This gives a lower pressure (between 2MPa and 4MPa)
- A high pressure coating process: in this process a liquid combustible is used (kerosene, white spirit, …) creating a much higher pressure (around 8MPa) resulting in a faster flow (700m/s to 900m/s).
The type of vhof coating process is determined by the expected characteristics of the treated surface. The higher the speed of the projected particles the denser (and more resistant) the surface will be.
HVOF applications
Hvof coatings are used to reduce the wear on parts or to improve the thermal resistance of the primary material of the surface. Hvof coatings can be applied in several layers making the surface more resistant. The more coating layers used the more the surface will reach the characteristics of the particles used.
Why do you need Rafinato Metal Services?
The quality of hvof coatings depends on a number of factors (pressure in the compression chamber, the mixture Oxygen/combustible, the flow of particles and the distance of the gun relative to the treated surface).
All these variables are very hard to master and critical in production of a durable and reliable part you can use.
At Rafinato Metal Services we have a highly qualified staff ready to study the details of your project/needs. We also created a network of 30 metal workshops in western Europe (spread over 5 countries) ready to treat the surfaces of your parts in the best conditions.
Do you need advice?
Rafinato is the solution! Go to our contact form, fill in your details and we will reach out to you to find will find the adequat supplier for you.