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Materials Science in Additive Manufacturing Measuring the porosity of AM components

Table 2. Methods for determining the open or total porosity depending on the pore size.
Procedure Pore size Porosity Density Advantages Disadvantages
range (nm) measurement measurement
Gas adsorption <50 Indirect Indirect Allows for specific measurement of No direct determination of porosity and
surface area and pore size; provides density; closed pores not measurable
additional information on porosity
Mercury intrusion 4 – 60,000 Direct Indirect Covers large pore area, direct Hazardous to health and environment;
measurement of open porosity and destructive process; closed pores not
indirect measurement of apparent measurable
density above it
Neutron and X-ray 1 – 100 Indirect Indirect Examination of the part structure at Very complex, expensive procedure;
scattering atomic level; allows conclusions to be radiation exposure
drawn about porosity and density
Scanning electron >10 Direct Indirect High resolution and depth of field for High costs and labor-intensive; no
microscope qualitative pore information direct density measurement
Light microscopic >2,000 Direct Indirect Measurement of open and closed pores; Only local porosity measurement;
image analysis wide application for many materials complex; no direct density measurement
Computed >1,000 Direct Direct Non-destructive density and porosity Only radiolucent materials measurable;
tomography analyses; spatial resolution and 3D expensive; time-consuming
imaging
Helium gas >1 Indirect Direct Very fast measurement, good No determination of pore distribution;
pycnometry reproducibility; non-destructive; highly limited sample size; closed pores cannot
accurate be measured
Volume saturation >2 Direct Indirect Simple and inexpensive measurement of No determination of pore distribution;
method open pores; non-destructive and accurate time-consuming and slow; closed pores
cannot be measured
Archimedes >100 Indirect Direct Simple and fast measurement; Inaccurate with very small or porous
method non-destructive; complex samples can be samples; influenced by surface tensions;
measured closed and small open pores cannot be
measured

When determining density and porosity, a distinction 2.3. Porosity evaluations of AM structures
must be made between direct and indirect measurement Within the scope of the materials for AM components
methods. Direct porosity measurement methods aim examined in this study, manual density measurements
to determine the porosity by direct measurement of according to Archimedes, specific micrograph analyses, and
the pore structure, for example, by imaging methods investigations with the gas pycnometer to determine density
(light microscopic image analysis, CT, scanning electron and porosity were most frequently documented. 6,7,17,21,22
microscope analysis) or mercury intrusion. Indirect
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measurement methods determine the porosity by Damon et al. carried out porosity tests
measuring another physical part property, such as density, specifically on FDM-printed parts made of 316L
and then calculate the porosity from this, for example, using stainless steel. The sintered parts were analyzed with
gas pycnometry, volume saturation methods, or gravimetric the help of micrographs, among other things. During
density measurement methods based on Archimedes’ the tests, a porosity of the parts of 0.5 – 1.7% was
principle. This density measurement method, also known determined, whereby a part density of the sintered
as the Archimedes method, is also a direct measurement 316L components of up to 99.5% can be achieved. The
method for determining the (apparent) part density. Neutron microstructure and pore structure of the components
and X-ray scattering are indirect methods for determining were also analyzed using micrographs. However, the
porosity, as they provide information about the structure of porosity of the parts was not validated using other
the material at an atomic or molecular level and then allow analytical methods, and the unsintered 316L green
conclusions to be drawn about the porosity. Gas adsorption parts were not analyzed.
is also an indirect measurement method that measures Gong et al. investigated the density of sintered 316L
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the specific surface area and pore size of components and FDM parts using a gas pycnometer and micrograph
provides additional information for characterizing porosity. analysis. A part density of 7.88 g/cm³ was measured for

Volume 4 Issue 2 (2025) 5 doi: 10.36922/MSAM025090010