Lucas M. Erich, Logan D. Winston, Daniel Oropeza
The field of powder metallurgy relies heavily on metal powder atomization to commercially produce suitable powder for subsequent processing. Atomization is unique among powder production techniques in offering both scalability and high quality. The process involves the breakup of a liquid into droplets, specifically molten metal into particles that subsequently solidify, by means of a secondary fluid or mechanical force. However, the mechanisms underlying this process are intricate, differ for each atomization technique, and are not fully understood. This review begins with an examination of the major atomization techniques (water, gas, plasma, centrifugal, and ultrasonic), describing the process fundamentals, historical development, governing mathematics, industry standards, current capabilities and limitations, and future outlooks of each. The literature review provides a comprehensive summary of the current state of atomization. Further, given the scarcity of direct comparisons between powders produced by different atomization techniques, this work provides an original experimental contribution. Ubiquitous powder metallurgy alloys 316 L stainless steel and Ti-6Al-4 V are examined, each sourced across four different atomization techniques in the same size fractions, including ultrasonic powder synthesized in-house. Powder size, morphology, and rheology are characterized via microscopy and ASTM rheology standards, illuminating the interplay between these powder properties and rheology, as well as their relation to the fundamentals of their respective atomization processes. The article concludes with an overarching outlook for the powder metallurgy and additive manufacturing communities, identifying key gaps (particularly the disconnect between industry and academia) and opportunities for enhanced collaboration to advance both atomization technology and fundamentals.