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

- The internal porosity of the powder feedstock is analysed.
- X-ray tomography is introduced and used as non-destructive testing tool.
- Quantification by image processing is applied.

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.