• 1
  • 2
Prev Next
Thermal Spray Intelligence Platform
FOC
Coatings for the Aeronautic Industry
Riblet-Surfaces for Improvement
PROCETS
TECNIOSPRING EUROPEAN PROJECT
CPT Opportunities
3D Tooling

Cold Gas Spray - CGS

Cold spray is a solid-state deposition process in which small powder particles (in the range of 5 to 50um) are accelerated to velocities in the order of 500 to 1200m/s in a supersonic jet of compressed gas onto a substrate where the powder particles deform and bond together rapidly building up a thick layer of deposited materials.

The metal powder particles are fed centrally, by a separate gas stream typically introduced into the high-pressure side of a de Laval converging-diverging nozzle where a preheated gas (usually air, He, N2, or mixture depending on the deposition material and gas temperature) in the range of 300-800ºC is compressed and will expand to supersonic velocities while decreasing in pressure and temperature. Such velocities can be reached due to the changes of geometry and Mach inside the nozzle. It has to be noted that the gas is heated not to heat or soften spray particles, but instead to achieve higher sonic flow velocities, which ultimately result in higher particle impact velocities. Since the contact time of the injected particles with the hot gas is short and the gas cools as it expands, it is considered that the particles temperature remains below its melting temperature. The term “cold spray” has been used to describe this process due to the gas stream’s exiting temperature (-100 to 100ºC).

The fact that this is a solid-state process will allow for a uniform, thick, porosity and oxide free coating and usually maintaining the same proprieties as those of the bulk material. Unlike the conventional deposition techniques, which require both kinetic (particle velocity) and thermal (temperature) energy in order to promote coating formation onto a substrate, the cold spray process simply uses the kinetic energy of the powder particles for the coating formation. The kinetic energy of the impinging particles is sufficient to produce plastic deformation and high interfacial pressures. Furthermore, because cold spray is a low-temperature process, i.e., does not use thermal energy, the obtained coatings are less porous, and present less oxidation and higher hardness. A wide variety of materials such as pure metals, metallic alloys, polymers and composites onto various substrate materials obtaining very high coating deposition rates, can be obtained using this novel deposition process.

 

 

Advantages:

- Low porosity and low oxide content coatings are obtained.

- Lower jet temperatures prevent decarburization and high impact velocities produce a relatively pore-free coating.

- High density, phase purity and homogeneous microstructure of cold spray coatings promote exceptional corrosion characteristics.

- Ability to deposit a wide range of materials with a stable molten phase.

- Ability to deposit on an wide range of substrates, even to temperature-sensitive materials: thermal energy in a single droplet is quite limited therefore avoiding thermal contraction.

- Very high deposition rates (the material is deposited as 10-100µm molten droplets).

 

Applications:

Applications in aerospace, defense, automotive and electronics industries.

- High-performance applications such as electrical/thermal conductivity, high-temperature oxidation protection and corrosion resistance and also electronic applications;

- Automotive industry in copper coatings as current-carrying thick films, zinc coatings for selective galvanizing to protect weld spots, production and repair of rapid tooling and thermal layers;

- Aerospace industry in oxidation-resistant coatings, high-thermal conductivity coatings for thermal management, and production and repair of critical components and parts.