AP&C

Coatings

Powdered metal coating techniques are generally classified under two types:

  • Cold spray coating
  • Thermal spray coating

 

Cold spray coatings

This is a solid-state coating process. A high-speed gas jet is used to accelerate cold powder particles towards a surface where metal particles are deformed and consolidate on the surface upon impact.

The process takes place at a temperature much lower than the melting point of the spraying material. Cold spray coating is especially useful for applications where parts are sensitive to the temperature of the process. A low oxygen content powder is very important for this process.

Applications

  • corrosion mitigation of sensitive materials
  • surface restoration and sealing
  • manufacture of sputtering targets
  • fabrication of busbars on heated glass
  • electrical and thermal conductive coatings
  • biomedical and biocompatible materials on orthopaedic implants, prosthesis and dental implants

Advantages

  • Safety due to low temperature process
  • Gradient deposits
  • Suitable for many substrate materials
  • High density, low porosity coatings
  • Minimal substrate distortion even at very low thickness
  • Minimal surface preparation needed
  • Safer for the environment
  • Metastable alloys can be deposited

Thermal spray coatings

With this process, coated materials are melted or heated, then sprayed onto a surface. This is mainly used for so-called thick coatings (over 50 micrometers). Thermal spray coatings are mainly classified in 4 categories according to the source of energy used:

  • Flame spraying
  • Wire-arc spraying
  • Plasma spraying
  • High-velocity oxy-fuel coating spraying (HVOF)

Applications

  • Gas turbine technology
  • Electronics industry
  • Aircraft industry
  • Biomedical
  • Carbon fibres composites
  • Electronics
  • Energy

Advantages

  • Versatility, almost any metal, ceramic or plastic can be thermal sprayed
  • Cost effective mean to repair worn components and incorrectly machined parts
  • Rapidity, around 3 to 60 lb/hr depending on the material and spray system
  • Good for parts that require porosity
  • Technology offers good wear and heat resistance
  • Clearance and dimension control
  • Corrosion and oxidation resistance
  • Good electrical properties (resistance and conductivity)

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