Abstract
Understanding the deposition mechanism of fine solid particles is essential for the effective use of the cold spray (CS) technique, which is used to synthesize dense and thick metallic coatings. As such, in this study, the deposition behaviors of spherical pure aluminum particles were investigated in detail in order to understand the deposition mechanism; these particles had a diameter of 1 mm and were deposited on five metallic substrate materials, during the CS-emulated high-velocity impact process. A single particle impact testing system, which is a modified single-stage light gas gun, was used to evaluate the deposition process. This evaluation confirmed that the critical velocities of Al particles vary significantly with the substrate material. In order to identify the dominant factors, the bonding energies, rebound velocities, plastic deformation experienced by the particles and substrates, and removability of the natural oxide films were evaluated. The results revealed that the critical velocities increased significantly with increasing Ar sputtering time required for complete removal of the natural oxide film; this time represents the removability of the film. This result confirms that, of the factors considered, the removability of the natural oxide film exerts the most influence on Al particle deposition on metallic substrates.
