High resolution pore size analysis in metallic powders by X-ray tomography

TLDR

Additive manufacturing quality hinges on the absence of internal defects, yet porosity in powder feedstock—though very low—has been linked to such defects and cannot be quantified by standard techniques. The study aims to quantify micro‑sized porosity in metallic powders to better understand defect origins and support quality control. High‑resolution (3 µm) X‑ray tomography visualises pores in large powder volumes, allowing their geometric features and volume fraction to be measured through image‑analysis routines. The approach outperforms conventional powder characterisation methods and demonstrates its strengths and limits across different imaging devices, materials, and analysis procedures.

Abstract

The deployment of additive manufacturing processes relies on part quality, specifically the absence of internal defects. Some of those defects have been associated with porosities in the powder feedstock. Since the level of porosity in the powder is generally very low, standard characterisation techniques such as pycnometry and metallography are not suitable for quantification. However, the quantification of such micro sized porosity in metallic powders is crucial to better understand the potential source of internal defects in final components and for quality control purposes. X-ray tomography with a 3 μm resolution offers the possibility to visualise pores in large volume of powder and to quantify their geometrical features and volume fraction using image analysis routines. This combination is unique and demonstrates the power of the approach in comparison to standard powder characterisation techniques. Results presented show the prospects and limits of this technique depending on the imaging device, material and image analysis procedure.