High pressure cold spray additive manufacturing

​Cold spray is a technique that accelerates powder particles towards a substrate using a supersonic compressed gas jet. Upon impact, the particles travelling at high velocities (200 to 1000m.s-1) experience extreme and rapid plastic deformation. They stack up to form a solid state deposit that is well bonded to the substrate and free of oxides (disturbed at impact).

cold spray setup [8]

The basis of the cold spray process [2–5] is the gas-dynamic acceleration of particles to supersonic velocities and hence high kinetic energies. It is also important to emphasize that the particles are not subjected to heating or melting mechanisms but to plastic deformations only. The substrate is not really heated by the gas exiting the gun (up to 200C). 

Particles adhere to the substrate only if their impact velocity is above a critical value. This varies between ~500 and 900 m/s, depending on the material and on the particles’ size (1 to 50µm).

Spray rates reach about 3–6 kg/h with deposition efficiency rates in the range of ~70/90%. 

Given the impact-fusion coating mechanism, only ductile metals or alloys are sprayed [6]:

• Metals (Al, Cu, Ni, Ti, Ag, Zn, Ta, Nb)
• Refractory metals (Zr, W, Ta)
• Alloys (steels, Ni alloys, MCrAlYs, Al-alloys) 

Blends of ductile materials (>50 vol.%) with brittle metals or ceramics are also used:

• (Cu-W, Al-SiC, Al-Al2O3)

A range of applications can be explored [7]:

• Repair of lightweight aerospace parts;
• Hard wear, anti-corrosion or biocompatible coatings;
• Thick metallic coatings of thermally sensitive components;
• Layer by layer additive manufacturing

 
They span across sectors such as aerospace, medical, automotive and motor sports, oil and gas, power generation…

References
[1] thermal spray fundamentals, springer, Pierre L. Fauchais, Joachim  V.R. Heberlein, Maher I. Boulos ISBN 978-0-387-28319-7
[2] Ga¨rtner F, Stoltenhoff T, Schmidt T, Kreye H (2006) The cold spray process and its potential for industrial applications. J Therm Spray Technol 15(2):223–232
[3] Champagne VK (ed) (2007) The cold spray materials deposition process. Woodhead Publishing Limited, England
[4] Alkhimov AP, Papyrin AN, Kosarev VF, Nesterovich NI, Shushpanov MM. Gas-dynamic spraying method of applying a coating. US Patent 5, 302,414, April 12.
[5] Stoltenhoff T, Kreye H, Richter HJ (1994) An analysis of the cold spray process and its coatings. J Therm Spray Technol 11(4):542–550
[6] Cartier M (2003) Handbook of surface treatments and coatings. ASME Press, New York, NY
[7] Davis JR (ed) (2004) Handbook of thermal spray technology. ASM International, Materials Park, OH
[8] Champagne VK Jr, Helfritch D, Leyman P, Grendahl S, Klotz B (2005) Interface material mixing formed by the deposition of copper on aluminum by means of the cold spray process. J Therm Spray Technol 14(3):330–335