9. Cold Sprayed Metal Coatings

Among various types of surface treatments available, thermal spraying techniques have been used for the past century in many industrial fields owing to their ability to produce coatings of several tens of micrometers to several millimeters in thickness. Such techniques use flames, arcs, plasma, and other methods to heat and accelerate particles. In contrast, cold spray (CS) techniques [1‐7], which have been attracting attention during the past 20 years, apply a deposition technology based on impacting particles at high velocities. That is, accelerating the particles using a relatively low-temperature and high-velocity working gas results in a significant difference from other thermal spraying methods. Because the gas temperature is lower than the melting point of the material particles, this technique is called a “cold” or low-temperature spray. It has also been called a kinetic spray, because of the coating formation through the kinetic energy of the particles. In this chapter, as an outline of the CS method, the basic principle, equipment, features, materials, application examples, and issues in the use of a cold spray are described. In addition, CS technology has been systematized to a certain extent, and readers are encouraged to refer to other specialized materials [2‐7] focusing on this area. In addition, as an additive manufacturing technique, a nearly net-shaped formation is also being studied using a thick coating as a possible feature of CS technology, which is briefly explained in the following.