Cold spraying belongs to the new generation of HVOF (high velocity oxy-fuel spraying). In cold spraying, the kinetic energy (i.e. the particle speed) is increased and the thermal energy reduced, resulting in nearly oxide-free spray coatings. This new development has become known as CGDS (the cold gas dynamic spray method).
Laboratory studies have shown that the coatings produced by CGDS bond extremely tightly and are extraordinarily dense. Whereas in hitherto conventional thermal spraying methods the powder needs to be heated in the spraying process to above its melting point, in CGDS the temperature of the gas must be kept significantly below the temperature at which the material melts. This means that the oxidation of the coating material and the oxide content of the sprayed coating are far lower. Furthermore, coated substrates do not undergo any material changes due to heat exposure.
The spray additive is heated by a gas jet at the right pressure to particle velocities of up to 1,000 m/s and coated on the surface as a continuous jet. The particle beam can be focused on cross-sections of about five millimetres. The spraying rate varies between 3 to 15 kg/h.