Cold spray (CS) is a relatively new deposition method, whereby materials can be deposited onto surfaces in a solid-state manner without heating above the melting temperature [6–8].
In this process, the feedstock material (in the form of powder) is accelerated to supersonic speeds in a converging–diverging nozzle using an inert carrier gas.
The gas and powder mixture is fed at high pressure into the nozzle inlet and made to expand in the internal channel; powder speed levels in excess of 1000 m/s can be reached at the nozzle exit.
When particles impact on a surface a plastic deformation process occurs.
Above a critical impact velocity for the powder-substrate combination the particles will bond to the surface, and form a coating.
CS has been tested with a number of materials, including high performance metals and alloys [6–9], composite materials [10,11] and also pure ceramics [12,13].
Using CS it is possible to produce oxygen- and thermal-sensitive coatings on different substrates without the necessity of special environmental conditions.