Effect of particle materials on deposition behavior and microstructural features of films prepared via vacuum kinetic spraying

Vacuum kinetic spraying (VKS) is a particle deposition process by which various materials can be deposited as films, even at room temperature. In this study, Al 2 O 3 (ceramic, completely brittle), Fe-based bulk metallic glass (BMG, brittle with some plastic deformability), and Ag (metal, completely ductile) were used as powder materials, and the effects of the particle materials on the deposition behavior and microstructural features of the film were investigated. Deposition tests were performed under identical experimental conditions, and the microstructural features were comprehensively analyzed. The deposition behavior and film microstructure of the three materials were completely different. The Al 2 O 3 film formed at the lowest deposition rate was extremely dense and comprised nanocrystals with a relatively low surface roughness, indicating fragmentation-dominant deposition. The deposition rate of Ag was between those of the other two materials, and the film consisted of relatively dense large grains with nanopores and a smooth surface, resulting from plasticity-dominant deposition. The deposition rate of BMG was considerably high, and the resulting film consisted of a porous structure with relatively large fragments and an extremely rough film surface. These features of BMG were attributed to the insufficient fragmentation or plastic deformation of the particles. Consequently, even under identical deposition conditions, the deposition rate and behavior and the resulting film microstructure vary depending on the particle materials. Therefore, the microstructural features of the film must be examined before selecting powder materials and fabricating films through process optimization for each material. • Three types of materials were used for coating; fully brittle (Al 2 O 3 ), ductile (Ag), and brittle with some plastic deformability (bulk metallic glass, BMG). • The impact velocities and deposition behaviors of each particles were evaluated using computer simulations and actual experiments. • The microstructures of each film were compared in detail. • Based on these findings, the deposition processes for each material with different characteristics were hypothesized.