| Résumé | Additive manufacturing community recognizes that better powder flowability leads to better final products. However, there is presently no agreement on what constitutes a good flowability. Indeed, AM machine users have reported that powders appearing to be identical may exhibit different spreading behavior in the machines. Flowability is not an intrinsic property and depends on many different factors including the conditioning of the powder, the measurement method and the environmental conditions during the tests. Consequently, significant variations have been reported from laboratory to laboratory but also within a same laboratory when using standard procedures to measure flow. Thus, there is a need to better understand flowability and develop reliable and relevant methods to qualify powders. One of the important factors affecting the flowability is the relative humidity. However, the impact of humidity on the flowability of powders for additive manufacturing has not been well documented and current standards are not taking this effect into account. This paper presents the impact of humidity on the flowability of titanium powders using various tests (Hall, Carney, apparent density, angle of repose, rheology, avalanche, spreadability). While the effect of humidity is significant, not all methods have the same sensitivity to the level of humidity. The paper also presents methods to measure the level of humidity and the effect of measurement method on the results. |
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