This review summarizes the electrodynamic mechanisms governing powder flowability in powder bed fusion (PBF) metal additive manufacturing, focusing on how surface oxide-film characteristics control electrical dissipation and recoating behavior. Based on in-situ particle image velocimetry (PIV) and electrical impedance spectroscopy (EIS) of representative gas-atomized (GA) and plasma rotating electrode (PREP) powders, we outline experimental evidence that oxide-film thickness and charge-relaxation characteristics strongly influence flow regimes, layer renewal, and powder-bed quality. We further organize a theoretical framework integrating electric-field–driven stress, dynamic cohesive effects, and nonlocal stress transmission, and show that it can account for plug-like regions observed in GA powders (effective plug thickness on the order of millimeters) using parameters obtained from EIS. In addition, the streamwise persistence length of the aligned flow region (Leff) is discussed as a diagnostic metric for assessing the limitation of local exponential-decay assumptions and the need for nonlocal stress transmission. The review provides a unified view linking oxide-film morphology, electrical properties, flow structure, and powder-bed quality, and discusses practical implications for designing high-flowability metal powders and managing recycled powders.
Akihiko CHIBA (Thu,) studied this question.