4. Powder

Even more so than in other thermal spray processes, the powder that ultimately leads to the coating plays a major role in cold spray, due to the specific characteristics of this deposition method: low temperature and very high spray velocity. Low temperature means that the particle's microstructure imposes a high degree of metallurgical heredity on the deposit, while the particle's shape and size (summarized under the Goethian term morphology) strongly influence the spraying speed, and therefore the conditions of deposit formation and, consequently, its properties. Some might call this the nobility of the particle. More generally, knowledge of the characteristics of particles/powders is essential to the development and control of their processing conditions.

Given the size of the particles, certain characteristics may require the use of special techniques to determine...