ARL Center for Cold Spray

Advantages

Cold spray offers several advantages over other coating systems and deposition processes. Because it is a low-temperature process, cold spray operates below the melting point of metals, requires no combustible fuels or gases, and results in very low porosity deposits. Its solid-state bonding feature, similar to explosive bonding, allows mechanical mixing of particles and substrate. High velocity impact results in plastic deformation of particles to disrupt oxide films and provides compressive residual stresses. Low temperatures assure that the crystalline structure of the particles does not change and that initially nano-structured particles result in nano-structured deposits. Cold spray can also be used to form high-density deposits, producing thick coatings with low oxide and porosity content and/or free-standing structures. These advantages are summarized as follows:

Low Temperature Process

  • Below Melting Point of Metals
  • No Combustion Fuels, Gases
  • Nano-structured particles do not fuse by melting
  • Crystalline structures not altered

Solid State Bonding

  • Mechanical Mixing of Particles and Substrate
  • Similar to Explosive Bonding
  • Plastic Deformation of Particles Disrupt Oxide Films

High Density Deposits

  • Form Thick Coatings at High Deposition Rates
  • Low Oxide and Porosity Content (‹1%)
  • Form Free-Standing Structures
  • Compressive Residual Stresses

The following figres show how these abilities can yield exceptional results.

Low Temperature Process

 

Comparison of Cold Spray and Thermal Spray:

The following graph presents the operating window for common metal spray technologies. Compared to conventional thermal sprays, cold spray is characterized by the lowest temperature and the highest velocity. The operating temperatures of conventional plasma, detonation, and High Velocity Oxygen Fuel produce melted particles, which shrink upon cooling, leaving high tensile residual stresses. Since particles are not melted for cold spray, the resulting deposits exhibit moderate compressive residual stress. In addition, the crystalline structure of cold sprayed particles remains largely unchanged during deposition, unlike that of the melted and resolidified particles in conventional thermal sprays.

Comparison of Cold Spray and Thermal Spray

The figure below illustrates how operation at the conditions above affect the deposited material.

 

Last Update / Reviewed: May 31, 2018