Assessing the robustness of powder rheology and permeability measurements

• Published in: Additive manufacturing 2020-10, Vol.35, p.101203, Article 101203
• Main Authors: Lefebvre, L.P., Whiting, J., Nijikovsky, B., Brika, S.E., Fayazfar, H., Lyckfeldt, O.
• Format: Article
• Language: English
• Subjects: Compressive strength; Elasticity; Environmental conditions; Flow charac-teristics; Intrinsic property; Limited information; Measurement conditions; Measurement methods; Permeability measurements; Powder flowability; Powder metallurgy; Powder metallurgy process; Repeatability; Reproducibility; Rheology; Round robin
• ISSN: 2214-8604; 2214-7810; 2214-7810
• DOI: 10.1016/j.addma.2020.101203

[Display omitted] •Variations were observed when measuring powder resistance to flow in different laboratories.•Deformation rate and aeration impacted the resistance to flow of the powders.•Humidity and powder sampling had limited impact on flow energy for the conditions investigated.•Powder handling affected the measurements and led to significant variations.•Permeability measurements were more robust and little affected by applied pressure. Powder metallurgy processes rely on powder flowability. However, flowability is not an intrinsic property and depends on the measurement conditions. Standards have been developed to adjust measurement methods to various flow conditions but there is presently questions whether current methods are adapted to the specific requirements of powder bed additive manufacturing. Rheology has been used to assess powder flowability but there is still limited information available on the robustness of the method. This paper presents the flow characteristics measured in five laboratories with a powder rheometer. Attempts were made to understand the sources of intra and inter laboratory variations and find ways to reduce them. The variations do not seem to be associated with sampling or environmental conditions. Experimental setup, calibration and/or the modification of the powder during handling could be associated with the variations observed. However, additional tests would be required to confirm the sources and improve the repeatability of the measurements.