Recommendations for the metallographic preparation of crack-like defects in PBF-LB/M additively manufactured alloy 625 builds
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Madeleine Giller Apprenticeship as a materials testing technician at the welding institute SLV Berlin-Brandenburg. After that, she studied materials science at the Berlin Institute of Technology. She graduated with a masters degree in materials science in 2012. Since November 2012 employment as engineer at the Metallography Laboratory of the Siemens Gas Turbine Works in Berlin. She has been appointed laboratory manager within the Berlin Testing Center of the Large Gas Turbine Engineering Group in 2014. Her main fields of expertise comprise failure analysis and microstructural investigations using the field emission scanning electron microscope.Erhan Cagliyan trained as a state-certified technical assistant for metallography and physical material analysis at the Lette-Verein in Berlin. He has been working in the laboratory of the Siemens gas turbine plant in Berlin for 6 years, where his work focuses on fibre analysis, quantitative image analysis, microstructure characterisation with the field emission scanning electron microscope and X-ray fluorescence analysis.
Abstact
Crack-like defects were found in powder bed fusion-laser beam/metal additive manufacturing built gas turbine burner components. This was somewhat surprising, since the subject material, Alloy 625, is readily weldable. The original equipment manufacturer responsible for the print job had a good track record and excellent experience with this particular alloy. From the findings obtained in the metallographic investigation that is the subject of this contribution it can be concluded that i) the crack-like defects may not be liquation or solidification cracks as initially thought (both hot cracking phenomena), but possibly lack of fusion defects, ii) after a first preparation step, the defects were not detectable with light optical microscopy, even after etching with Kalling’s II reagent, iii) only after re-polishing using oxide particle suspension, or, alternatively, after reverse electrolytic etch with the anode and cathode swapped, using Kalling’s II reagent as electrolyte (Kalling’s II modified, a.k.a. Ätzen von Alloy 625 – Ätzlösung nach Boromir – Boromir’s etch), defects became detectable, and iv) only observation in the scanning electron microscope allowed characterization of the defects as lack of fusion rather than hot cracking.
Kurzfassung
In durch pulverbettbasiertes Schmelzen von Metall mittels Laserstrahl (PBF-LB/M) additiv gefertigten Gasturbinenbrennerkomponenten wurden rissartige Defekte festgestellt. Angesichts der Tatsache, dass der entsprechende Werkstoff Alloy 625 gut schweißbar ist, war das etwas überraschend. Der für den Druckauftrag verantwortliche Erstausrüster (OEM) hatte mit der entsprechenden Legierung eine gute Erfolgsbilanz und sehr gute Erfahrungen vorzuweisen. Aus den Ergebnissen der metallographischen Untersuchung, dem Gegenstand dieses Beitrags, können folgende Schlussfolgerungen gezogen werden: i) Bei den rissartigen Defekten handelt es sich unter Umständen nicht wie zunächst angenommen um Wiederaufschmelz- oder Erstarrungsrisse (beides Heißrissmechanismen), sondern möglicherweise um Bindefehler; ii) nach einem ersten Präparationsschritt waren die Defekte selbst nach dem Ätzen mit Ätzmittel nach Kalling II nicht im LOM erkennbar; iii) erst nach erneutem OPS-Polieren oder alternativ nach einer umgekehrten elektrolytischen Ätzung mit vertauschter Anode und Kathode und Ätzmittel nach Kalling II als Elektrolyt (Ätzmittel nach Kalling II, modifiziert, auch bezeichnet als Ätzen von Alloy 625 – Ätzlösung nach Boromir) waren die Defekte zu erkennen; iv) nur die Betrachtung im Rasterelektronenmikroskop ermöglichte eine Charakterisierung der Defekte als Bindefehler und nicht als Heißrisse.
About the authors
Madeleine Giller Apprenticeship as a materials testing technician at the welding institute SLV Berlin-Brandenburg. After that, she studied materials science at the Berlin Institute of Technology. She graduated with a masters degree in materials science in 2012. Since November 2012 employment as engineer at the Metallography Laboratory of the Siemens Gas Turbine Works in Berlin. She has been appointed laboratory manager within the Berlin Testing Center of the Large Gas Turbine Engineering Group in 2014. Her main fields of expertise comprise failure analysis and microstructural investigations using the field emission scanning electron microscope.
Erhan Cagliyan trained as a state-certified technical assistant for metallography and physical material analysis at the Lette-Verein in Berlin. He has been working in the laboratory of the Siemens gas turbine plant in Berlin for 6 years, where his work focuses on fibre analysis, quantitative image analysis, microstructure characterisation with the field emission scanning electron microscope and X-ray fluorescence analysis.
References / Literatur
[1] Ramsperger, M.; Eichler, S.: Electron Beam Based Additive Manufacturing of Alloy 247 for Turbine Engine Application: From Research towards Industrialization. Metallurgical and Materials Transactions 54 (2023), 10.1007, s11661-022-06955-0.10.1007/s11661-022-06955-0Search in Google Scholar
[2] Shaji Karapuzha, A.: Personal communication, August 26, 2024.Search in Google Scholar
[3] Heidloff, A.: IN 625 Powder Lot #68 Cracking Issue. Linde AMT internal communication, August 12, 2024.Search in Google Scholar
[4] Neidel, A., Giller, M., Cagliyan, E.: Metallurgical Failure Investigation of Small-bore Piping (SBP) in Diesel Hydrotreating Unit (DHT). Internal report BLN MT/2023/0118. Berlin, April 28, 2023.Search in Google Scholar
[5] Cagliyan, E.; Fischer, B.; Giller, M.; Neidel, A.: Metallurgical failure investigation of small-bore piping (SBP) inadieselhydrotreatingunit(DHT) ofanoilrefinery. Pract. Metallogr. 61(2024) 8, pp. 522–542. DOI:10.1515/pm-2024-004610.1515/pm-2024-0046Search in Google Scholar
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[7] Fischer, B.: PeziDat Etchant Recipe, published in September 2023.Search in Google Scholar
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[9] Cagliyan, E.; Giller, M.: Metallographic Specimen Preparation and Evaluation of PBF-LB/M Printed Samples. Implementing Procedure LAB-10001, Revision 03, January 9, 2024.Search in Google Scholar
© 2024 Walter de Gruyter GmbH, Berlin/Boston
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- Recommendations for the metallographic preparation of crack-like defects in PBF-LB/M additively manufactured alloy 625 builds
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- Cloeren Technology’s 20th anniversary
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Articles in the same Issue
- Contents
- Editorial
- Editorial
- Optimizing the design of the selective melt dispersion (SMD) process based on metallographic investigations of additively manufactured 316L steel samples
- Comparison of etchants for corrosion-resistant stainless steels in medical engineering
- Investigation on the impact of parameters of FSW on microstructural transitions and the strength of CDA 101 joints
- Failure Analysis
- Recommendations for the metallographic preparation of crack-like defects in PBF-LB/M additively manufactured alloy 625 builds
- Picture of the Month
- Picture of the Month
- People
- Cloeren Technology’s 20th anniversary
- News
- News
- Meeting Diary
- Meeting Diary
