(2b) Characterization of Powders for Additive Manufacturing

Powder-based additive manufacturing (AM) processes like selective laser sintering (SLS) of polymers, selective laser beam melting of metals (SLM) or selective electron beam melting of metals (SEBM) allow for freedom of design and the manufacture of parts with adequate mechanical properties and dimensional accuracy. Within this contribution, powder requirements for AM processes, resulting structure-property relationships and appropriate methods for powder characterization will be discussed.

The effect of particle size, particle shape and surface functionalization on bulk solid properties (flowability, packing density) will be outlined in detail for polymer powder systems including commercial PA12 laser sintering powder and PE powders, and TiAl6V4 powder for SEBM. Possibilities to assess AM processability are exemplarily demonstrated for polymer powder systems to be used in SLS. The capabilities of a Schulze ring shear tester, a powder tensile strength tester to assess powder flowability and a model experiment mimicking the powder deposition process in AM are discussed. The possibilities of dry particle coating as an efficient method to optimize powder flowability and bulk density are demonstrated. Moreover, the effect of structural properties of the polymer (e.g. crystallinity, molar mass) on thermal and rheological properties (melting behavior, coalescence), appropriate analytical methods for characterization and the resulting implications for SLS processability are addressed.

Powder properties, AM processability and part properties are closely connected: powders of good flowability and high bulk density are mandatory to obtain dense devices.

Schmidt, J.; Sachs, M.; Fanselow, S.; Zhao, M.; Romeis, S.; Drummer, D.; Wirth, K.-E.; Peukert, W., Chemical Engineering Science 156 (2016) 1–10.

Blümel, C.; Sachs, M.; Laumer, T.; Winzer, B.; Schmidt, J.; Schmidt, M.; Peukert, W.; Wirth, K.-E., Rapid Prototyping Journal 21 (2015) 697–704.