What Does Cold Spraying Mean?
Cold spraying is a high-kinetic-energy, solid-state coating process in which a high-speed gas jet is used to accelerate metal particles toward a metallic or non-metallic substrate upon which the particles plastically deform and consolidate on impact. The applications range from rebuilding worn-out parts, providing corrosion protection, abrasion protection and other surface protection coatings, to improving properties such as thermal and electrical conductivity.
Cold spraying is also known as gas dynamic spraying, kinetic energy metallization, high velocity powder deposition and kinetic spraying.
Corrosionpedia Explains Cold Spraying
Cold spraying is a material deposition technique where tiny particles of 1 to 40 microns diameter are propelled to a substrate using high-pressure gases. The particles, which start at temperatures below the material's melting point, are placed in a nitrogen or helium gas stream which is then heated and accelerated through a supersonic nozzle at speeds of 500 to 2500 meters/second.
As the particles impact the substrate, they experience rapid plastic deformation and disrupt the thin surface oxide film usually present in metal and alloy surfaces. The kinetic energy stored in the particles deforms them and heats their surfaces to the point that they weld to the substrate.
A cold spraying system can be designed as a fixed, portable, manual or robotic system. A typical system consists of:
- Powder feeder
- Source of compressed gas
- Gas heaters
- Supersonic nozzle
- Spraying chamber with motion system
- Spray parameters monitor
- Control system
The quality of the cold-spayed coating and the deposition efficiency depend on:
- Gas type
- Particle size
- Substrate and feedstock material characteristics
- Nozzle design
- Standoff distance
- Deposition kinetics
Advantages of cold spraying include:
- Low-temperature process that does not involve bulk particle melting
- Forms dense deposits with low oxygen content, free of residual tensile stress, no grain growth and no re-crystallization zones
- Ability to deposit temperature-sensitive and advanced materials
- Oxygen-free coatings desirable for corrosion protection
Cold spraying processes are used for corrosion protection, restoration and production of parts in the medical, electronics, aerospace, automotive, petrochemical, energy, military and other industries.