Thermal Spraying Processes

Detonation Spray

Oxygen and fuel (acetylene most common) is fed into the barrel along with a charge of powder. A spark is used to ignite the gas mixture and the resulting detonation heats and accelerates the powder to supersonic velocity down the barrel. A pulse of nitrogen is used to purge the barrel after each detonation. This process is repeated many times a second. The high kinetic energy of the hot powder particles on impact with the substrate results in build up of a very dense and strong coating.

Characteristics of Detonation Spray Coating :

Material Form Powder
Heat Source Charge Detonation
Flame Temperature (°C) 1,500 to 4,000
Particle Velocity (m/sec) 600 to 1,200
Porosity (%) < 1
Coating Adhesion (MPa) > 70

Advantages :

  • Excellent bond strength
  • Very dense coatings
  • Better coating characteristics of hardness, wear & corrosion resistance
  • Versatile process, ensuring wide range of coatings
  • Low process temperature enables spraying of precision components
  • Higher thickness coatings easily possible

Disadvantages :

  • Very slow process as the coating is intermittent
  • Comparatively low coating efficiency
  • Very high noise emission

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