Roles of Particle Size Distribution in Bimodal Feedstocks on the Deposition Behavior and Film Properties in Vacuum Kinetic Spraying

Vacuum kinetic spray (VKS), also called aerosol deposition method, is a spray process that makes it possible to fabricate dense ceramic films at room temperature. Although the deposition rate of VKS is better than conventional ceramic coating processes, the deposition properties are still poor for industrial use. In this respect, this work investigates the role of particle size on the deposition behavior by blending two alumina powders having different sizes. It results in suggestions for increasing the deposition efficiency and rate. The microstructure and mechanical properties of films revealed that nanosized particles directly took part in deposition and participated in increasing the deposition rate despite the low adhesion between crystallites. In contrast, relatively large submicron-sized particles mainly contributed to the coating consolidation via severe friction, which strengthened the fragment bonding. Submicron-sized particles also were indirectly deposited as crystallites after sufficient fragmentation. Therefore, it is suggested that the deposition behavior and film properties in VKS can be controlled by adjusting the mixing ratio of two alumina powders with different particle size ranges.