Additive manufacturing: powders at the heart of material-laser interaction

What is additive manufacturing?

Additive manufacturing consists in elaborating a part by successive stacking of powder fused by a laser beam. As opposed to traditional processes based on the removal of material, additive manufacturing has several advantages.

Indeed, benefiting today from a good level of maturity, this technology offers an unequalled freedom of design and has found numerous applications in demanding markets such as aeronautics, space, medical, automotive, …

The quality of the powders, which can be metallic, ceramic or polymeric, is a crucial point for this process. At the heart of the material-laser interaction, the powders must respect a chemical composition, a morphology, a granulometry and a minimal intraparticle porosity.

How to guarantee the quality of additively manufactured parts?

In order to guarantee the quality of the parts produced, the control of recycled or non-recycled metal powders is a major challenge to achieve the expected performance. Therefore, the parameters regularly assessed are :

  • the chemical composition determined by ICP-AES, ICP-MS and elemental analyzers (C/S, N/O and H). These analyses make it possible, to begin with, to obtain the chemical composition of the powder initially used but also of that progressively recycled,
  • the granulometry, generally carried out by laser granulometry according to the ISO 13320 standard,
  • the flowability characterized by a flow time, it can be measured by means of a calibrated funnel of the cone type:
    1. Hall funnel according to ISO 4490 and ASTM B 213
    2. Carney cone according to ASTM B 964 (this last cone being of interest for aluminium powders for example)
  • the apparent density and the tapped density allowing to characterize by mechanical effect the aptitude of a powder to organize itself by chasing the air between the grains. These tests are carried out using a volumetric compaction meter according to ASTM B 527 and ISO 3953. The Hausner index corresponds to the ratio of the packed density and the apparent density,
  • the true density determined by pycnometry according to ISO 12154 or ASTM B 923. This value allows to calculate, with the help of the theoretical density (of a massive material for example), the internal porosity rate, 
  • the morphology qualified by Scanning Electron Microscopy (SEM-FEG) and Optical Microscopy. It allows to appreciate the granulomorphology, the sphericity, the satelliteness, the presence of contaminant, …
  • the microstructure characterized by a metallographic examination. It has a significant impact on the final mechanical properties of the parts produced.

As suggested by the NF E 67-010 standard presenting the technical specifications of powders for additive manufacturing applications, these tests can also be completed by measurements of specific surface, humidity, …

FILAB supports you in the analysis and characterization of your metal powders.

FILAB dispose d’une expérience significative dans la mise en œuvre de ces différentes techniques et bénéficie d’un réel savoir-faire d’expertise reconnu dans le cadre de nos accréditations COFRAC et de l’agrément SAFRAN (notamment selon les spécifications Ma-0015). FILAB peut vous accompagner dans vos besoins d’analyse de poudres métalliques et d’expertise associés aux activités de fabrication additive.

Pour plus d’informations, contactez notre expert Emmanuel Buiret

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