Ultrasonic atomization - a novel powder producion method with low cooling rates advantageous for CS

Thermal spray technologies benefit from spherical powder shapes with a narrow particle size distribution. Metal powders with such properties can only be obtained via gas atomization, which usually requires industrial facilities and a high investment in materials and inert gas for single atomization processes. Typically, such processes are characterized by a wide particle size distribution (PSD), limiting the amount of powder usable for thermal spray processes from each atomization run. Ultrasonic atomization, on the other hand, offers the ability to atomize materials economically on a smaller R&D scale, which is suitable for novel powder alloy development. It is also capable of atomizing metals and metal matrix composites across all ranges of materials, from Sn and Mg to refractory materials and high-entropy alloys. Thanks to arc melting capabilities and low-frequency induction furnaces, recycled feedstock can be converted into high-value spherical powders. During atomization, cooling rates are 2-3 orders of magnitude lower than gas atomization, which might benefit cold spray processes thanks to the lack of metastable phases and lower hardness of atomized powders. Two case studies, including X65Q steel and aluminum alloy, will be presented, indicating the differences in powder production methods for cold spray coatings.