Flame powder spraying

In this process the spray material is fed in powder form through the gun using a transport gas injecting it centrally into a burning gas/oxygen mixture, where it is melted and delivered onto the substrate.

Flame powder spraying2

Because nickel-based and cobalt-based meltable alloys and ceramic materials cannot be produced in wire form powder spraying was developed in 1956. Over the years powder spraying has been enhanced to include many other types of spraying powders. The way the powder spraying system works is similar to that of a wire spraying system (see Autogenous wire spraying).

Process properties

Material Form: Powder
Thermal energy source: by combustion of a fuel and oxygen
Process fuel: propane, hydrogen, acetylene
Process temperature: < 4,000 ºC
Spray particle speed: < 50 m/s

Features

  • Micro porous lamellar structure
  • Relatively high degree of oxidation in the coating
  • Moderate tensile strength
  • Good compressive strength
  • Low elongation properties
  • Versatile and with a wide choice of materials
  • Relatively inexpensive thermal spraying process
  • Transportable process, spraying on location is possible

Features of fused coating

  • Metallurgical bond with the substrate
  • Resistant to line and point loads
  • Low resistance to impact loads
  • Homogeneous and closed structure

Typical coatings

  • Fused alloys NiCrBSi (Fusing, Self-fluxing)
  • Nickel-based alloys
  • Various stainless steel alloys
  • Cermets, carbides (hard metals)
  • Ceramic coatings (oxides)
  • Abradable coatings (abradables such as nickel graphite, AlSi polyester)

Applications

  • Sealing moving surfaces to prevent seals from leaking
  • Improvement of wear resistance and chemical protection of ball valves
  • Boiler walls of incinerators against high-temperature erosion and chemical degradation
  • Repairs and dimension corrections of worn drive shafts and bearing seatings with nickel-based alloys

Autogeen Poederspuiten

 

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