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Combustion Wire (Flame) Thermal Spray Process
The Combustion Wire Thermal Spray Process is the spraying of molten metal onto
a surface to provide a coating. Material in wire form is melted in an oxy-acetylene
flame and atomized using compressed air to form a fine spray. When the spray contacts
the prepared surface of a substrate material, the fine molten droplets rapidly solidify
forming the coating. This process is referred to as a cold process (relative to the
substrate material being coated) as the substrate temperature can be kept low during
processing avoiding damage, metallurgical changes and distortion to the substrate material.
First invented in 1910 by Schoop in Switzerland, this process has been
extensively used in the past and today for machine element work and anti-corrosion coatings.
Common Materials
- Zinc and Aluminum for anti-corrosion cathodic coatings on steel.
- Nickel/Aluminum composite wire for bond coats and self-bonding coatings.
- Molybdenum for bond coats.
- Molybdenum for hard bearing applications, excellent resistance to adhesive wear, often used on piston rings, syncromesh cones and journals.
- High-Chromium Steel for many applications requiring hard and wear resistant coating.
- Bronzes, babbitt for bearing applications.
- Stainless steel, nickel and monel for anti-corrosion and wear.
- Aluminum and Nickel/Aluminum for heat and oxidation resistance.
- Ceramics and Cermets can also be used in rod or composite wire form.
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Advantages
- Wire form is typically less expensive than powder.
- Deposit efficiency is very high.
- Widely considered the best method of applying pure molybdenum coatings for wear resistance.
- Cold process avoids damage, metallurgical changes, and distortion to substrate material.
- High system portability.
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Limitations
- Limited to materials supplied in wire or rod form.
- Not capable of the low oxide, high-density, and high-strength coatings such as those obtained by plasma spray.
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