Comparison of porosity evaluation techniques for L-PBF manufacturing
Résumé
Porosity is a major concern in additively manufactured (AM) parts; therefore, its accurate detection and
measurement becomes extremely crucial for ensuring the safety of the part. In this work, we have manufactured
several AM samples of AlSi7Mg in the form of small cylinders (10 mm diameter) by modifying each time few
relevant fabrication parameters.
The Archimedes method is traditionally used as a classical and low cost technique for density (or porosity)
determination. Although fast in terms of time and data processing steps, its accuracy is somewhat limited and it
gives only a global information. Especially, it does not provide information about the distribution and sizes of
the pores.
X-ray computed tomography, on another hand, is a powerful but expensive tool for holistic measurements of
pores. We have analysed the AM samples first with laboratory micro-tomography and we have compared the
results to those of the Archimedes method. In addition, an ultra-high resolution (2.3 µm) tomography has been
obtained from synchrotron CT to cross-check the effect of resolution on porosity determination when compared
with laboratory X-ray CT.
On a different line of investigation, the Resonant Ultrasound Spectroscopy (RUS) technique is also suitable for
fast porosity evaluation, since the density reduction modifies the resonance spectra. In this work, the focus is
on the validation of the information obtained from all the techniques in order to assess the practical limitations
of each of the techniques for density evaluation.
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