It was now possible to spray ceramic materials such as Aluminium Oxide (Al2O3), Titanium Dioxide (TiO2), Chromium Oxide (Cr2O3) and many more. These “Oxide Ceramics” enabled engineers to create almost totally chemically inert coatings that had a low coefficient of friction and were hard wearing.
It was also now possible to spray carbide coatings, the most common being Tungsten Carbide (WC). Although Tungsten Carbide in isolation cannot be thermally sprayed because it doesn’t “soften” with heat, it can however be sprayed in a “matrix” metal allowing extremely hard coatings to be deposited with particles of Tungsten Carbide embedded within a more ductile matrix material.
Due the Combustion Powder system using a powder as it’s feed material, there is no requirement for compressed air to atomise the particles as in the case of the Combustion Wire system. This makes the Combustion Powder system much quieter and was often used in open workshops where the Combustion Wire system would be too noisy.
The most common fuel gas used with this type of system is acetylene (C2H2) but hydrogen (H2) is sometimes used when “cleaner” coatings are required.
Combustion powder properties table
Principle of operation
The Combustion Powder system feeds a powdered material into the centre of an Oxy-Fuel Gas flame. The flame provides both the Thermal and Kinetic energies (Heat and Speed) for the particles.
The powder is transported to the nozzle on a “carrier flow”. In the lower cost systems this can be a tapping from the oxygen feed. In the case of the more expensive systems a dedicated Powder Feed Unit is used to transport the powder on an Argon or Nitrogen carrier gas flow.
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