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Practical application of an automated 3D metallography system for the reconstruction and microstructural analysis of porosity in a sintered steel

  • A. Lemiasheuski

    Anton Lemiasheuski (born in 1992) graduated in mechanical engineering at HTW (Hochschule für Technik und Wirtschaft) Berlin in 2023 and start his PhD in the same year. Since 2023 he is an employee at HTW Berlin and do his research at BAM (Bundesanstalt Für materialforschung und -prüfung) in 3D-metal-lography.

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    , F. Wehrkamp

    Fabian Wehrkamp (born in 2000) completed his bachelor's degree in mechanical engineering at the HTW (Hochschule für Technik und Wirtschaft) Berlin in 2024. From January to May of that year, he researched at the BAM (Bundesanstalt für Materialforschung und -prüfung) on the topic of “Three-dimensional quantitative microstructural analysis of a sintered material made of Astaloy” for his bachelor’s thesis.

    , E. Bajer , M. Buchheim , E. Sonnenburg , A. Göbel , I. Porohovoj , D. Bettge and A. Pfennig
Published/Copyright: July 25, 2025
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Abstract

In the 3D microstructural analysis of a digital twin of porosity in the sintered steel Astaloy CrA, pore shape, average pore size as well as pore distribution will be analyzed. Porosity plays a major role in powder-metallurgical materials since it greatly impacts the mechanical properties of these materials and therefore represents a key parameter in their characterization. Based on the robot-assisted automated serial sectioning and imaging (RASI) system of the Federal Institute for Materials Research and Testing (BAM, Bundesanstalt für Materialforschung und Prüfung) in Berlin, the technique of metallographic serial sectioning will be used to image the microstructure and reconstruct a digital 3D twin from the stack of images obtained. Compared with an individual 2D microsection, the quantitative microstructural analysis of this 3D twin will enable more accurate conclusions on the shape, size and distribution of pores. This paper will detail the key steps in 3D microstructural analysis, including the metallographic preparation routine, the imaging technique, image alignment as well as the segmentation of pores. After the methodology has been described, the results of the quantitative microstructural analysis will be presented and the validity of quantitative parameters of 3D and 2D images will be compared and discussed. The analysis of more than 10,000 pores revealed a correlation between pore shape and pore size. It was also found that a 2D representation of the material surface is insufficient for a precise quantitative characterization of porosity.

Kurzfassung

In der 3D-Gefügeanalyse eines digitalen Zwillings von Poren in einem Sinterstahl des Typs Astaloy CrA werden sowohl die Porenform als auch die durchschnittliche Porengröße und -verteilung analysiert. Die Porosität spielt in pulvermetallurgischen Werkstoffen eine große Rolle, da sie erheblich die mechanischen Eigenschaften beeinflusst und daher bei der Charakterisierung dieser Werkstoffe ein wichtiger Parameter ist. Basierend auf der Verwendung des Robot-Assisted Automated Serial-Sectioning and Imaging (RASI)-Systems der Bundesanstalt für Materialforschung und Prüfung (BAM) in Berlin, wird das metallographische Serienschnittverfahren genutzt, um das Gefüge aufzunehmen und aus dem Bildstapel einen digitalen 3D-Zwilling zu rekonstruieren. Verglichen zu einem 2D-Einzelschliff ermöglicht die quantitative Gefügeanalyse dieses 3D-Zwillings präzisere Aussagen zu Porenform, -größe und -verteilung. Diese Arbeit beschreibt die wesentlichen Schritte, die für eine 3D-Gefügeanalyse nötig sind, darunter die metallografische Präparationsroutine, das Bildgebungs-Verfahren, das Alignment der Bilder sowie die Segmentierung der Poren. Im Anschluss an die methodische Darstellung werden die Ergebnisse der quantitativen Gefügeanalyse präsentiert und ein Vergleich zwischen der Aussagekraft der quantitativen Parameter von 3D- und 2D-Abbildungen diskutiert. Bei der Analyse von über 10.000 Poren konnte eine Korrelation zwischen der Form und der Porengröße aufgezeigt werden. Weiterhin konnte aufgezeigt werden, dass eine 2D-Abbildung der Werkstoffoberfläche nicht ausreichend für eine eindeutige quantitative Beschreibung der Porosität ist.

About the authors

A. Lemiasheuski

Anton Lemiasheuski (born in 1992) graduated in mechanical engineering at HTW (Hochschule für Technik und Wirtschaft) Berlin in 2023 and start his PhD in the same year. Since 2023 he is an employee at HTW Berlin and do his research at BAM (Bundesanstalt Für materialforschung und -prüfung) in 3D-metal-lography.

F. Wehrkamp

Fabian Wehrkamp (born in 2000) completed his bachelor's degree in mechanical engineering at the HTW (Hochschule für Technik und Wirtschaft) Berlin in 2024. From January to May of that year, he researched at the BAM (Bundesanstalt für Materialforschung und -prüfung) on the topic of “Three-dimensional quantitative microstructural analysis of a sintered material made of Astaloy” for his bachelor’s thesis.

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5 Acknowledgements

The authors would like to thank Evgenia Bajer for preparing and providing the meta data and Romeo Saliwan Neumann for the images obtained by scanning electron microscopy which formed the basis for the results presented in the paper Challenges and possibilities of the manual metallographic serial sectioning process using the example of a quantitative microstructural analysis of graphite in cast iron (original title: Herausforderungen und Möglichkeiten des manuellen metallografischen Serienschnittverfahrens anhand einer quantitativen Gefügeanalyse der Grafite eines Gusseisens). The authors also acknowledge Ms. Bajer’s and Mr. Neumann’s support throughout the entire project.

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5 Danksagung

Hiermit wird Evgenia Bajer ein großer Dank für das Präparieren und Bereitstellen der Metadaten ausgesprochen und Romeo Saliwan Neumann für die erzeugten Bilder am Rasterelektronenmikroskop, die in der publizierten Arbeit Herausforderungen und Möglichkeiten des manuellen metallografischen Serienschnittverfahrens anhand einer quantitativen Gefügeanalyse der Grafite eines Gusseisens für die Ergebnisfindung verwendet wurden. Ebenfalls wird beiden für die Unterstützung während des gesamten Projekts gedankt.

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Received: 2024-11-16
Accepted: 2025-01-15
Published Online: 2025-07-25
Published in Print: 2025-07-28

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