Effect of Substrate Surface Oxide Film Thickness on Deposition Behavior and Deposition Efficiency in the Cold Spray Process

The mechanism of cold spray deposition is not yet completely understood. The impinging velocity and deformation behavior of the particles are believed to be critical deposition conditions. However, such substrate conditions as oxide-film thickness and mechanical properties may also affect cold spray deposition. In this study we investigated the effect of substrate conditions, especially oxide film thickness, on the deposition process. The efficiency of deposition and the relationship between the impinging position of the particles and the number of particles deposited were investigated for two substrates coated with oxide films of different thickness; the particles were deposited sparsely on the substrates. Results showed that efficiency of deposition was lower for the oxide film with the greater thickness. Deposition tendency was also associated with impinging velocity, i.e., the critical velocity on which oxide film thickness depends; this is the reason for the different efficiency of deposition. An oxide film may inhibit deposition on a new surface. These results indicate that oxide film thickness has a substantial effect on the efficiency of deposition on the substrate. They also imply that creation of a newly-formed surface is important to the deposition process.