The Cold Spray Revolution
The deposition of metal powders onto surfaces has been done by thermal spray for over 100 years. In this process, metal particles are melted and blown onto the coated surface. Thermal spray processes thus apply engineered coatings to modify the surface properties of an item. These coatings can provide such properties as enhanced wear resistance, thermal barriers, electrical/thermal conductivity, hard-chrome replacement, and corrosion protection. The coatings can be applied to turbine blades, shaft seals, medical implants, etc.
The extreme heat required in thermal spray can compromise the powder and substrate characteristics. Cold spray was introduced 30 years ago as a solution to prevent heat damage. Cold spray accelerates powder particles to very high velocity in a supersonic nozzle, and a deposit is formed when the particles impact on the surface. Cold spray material deposition differs significantly from thermal spray deposition systems in that the cold spray process does not melt particles, particle velocities are very high, and the gas/particle jet plume has a relatively low temperature. Cold spray can thus be used in applications with heat-sensitive substrates, or applications that do not allow heat-modified deposits. The impact of the consolidation of high-velocity, solid state particles yields cold spray depositions with high strength, low porosity, and minimal residual stress.
The Army Research Laboratory (ARL) was the first Department of Defense (DoD) facility to employ cold spray, and has demonstrated its use for many military and commercial applications. This presentation will describe the cold spray process and the coatings that it can produce. Several applications developed at ARL will be shown.