Investigation of the rotating drum technique to characterise powder flow in controlled and low pressure environments

Abstract

Powder bed fusion, the most popular technique in metal additive manufacturing, utilises two main energy sources: laser or electron beam. The laser powder bed fusion process is typically conducted under inert gas-filled environment, while electron beam melting (EBM) process is operated in vacuum. Regardless of energy source, powder flowability is a major concern as it affects the final product quality. The rotating drum, a tool to characterize flowability and assess powder behavior during recoating, is conducted in ambient air environment, which inaccurately mimics these processes. This work investigated Inconel 625 and Ti6Al4V in atmospheric (air/argon) and low-pressure environments. The gas type did not affect the powders' dynamic flow behavior, however, a systematic difference existed in low-pressure environment especially with smaller particle size. As current research explores finer powder cut in EBM processes, new ways to characterize powder flow in vacuum should be considered to optimise powder spreading in EBM environment.