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Analysis of the Crack Initiation at Non-Metallic Inclusions in High-Strength Steels

  • P. Grad , B. Reuscher , A. Brodyanski , M. Kopnarski and E. Kerscher
Published/Copyright: May 23, 2013
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Practical Metallography
From the journal Practical Metallography Volume 49 Issue 8

Abstract

High-strength steels exhibit different fracture surface characteristics under cyclic load when failure is initiated by non-metallic inclusions depending on the lifespan. These can be attributed to different crack propagation mechanisms. These characteristics are correlated with the short and long crack propagation. As far as the short crack is concerned, the mechanism of the discontinous decohesion of carbides in the immediate vicinity of the inclusions and the merging of the resulting microcracks to form a macrocrack is discussed. This postulated mechanism is investigated by means of a combination of scanning electron microscope (SEM) analyses of the fracture surface and target preparation by means of focused ion beam (FIB) by a detailed resolution of the local microstructure around the crack-initiating inclusion and the crack path.

Kurzfassung

Unter zyklischer Beanspruchung zeigen hochfeste Stähle bei einem Versagen initiiert von nichtmetallischen Einschlüssen in Abhängigkeit von der Lebensdauer unterschiedliche Bruchflächenmerkmale auf, die auf unterschiedliche Rissausbreitungsmechanismen zurück zu führen sind. Diese Merkmale werden mit dem Kurz- und dem Langrisswachstum korreliert, wobei im Kurzrissbereich als Mechanismus die diskontinuierliche Ablösung von Karbiden in der näheren Umgebung der Einschlüsse und ein Zusammenwachsen der so gebildeten Mikrorisse zu einem Makroriss diskutiert wird. Durch Kombination von Bruchflächenanalysen im Rasterelektronenmikroskop (REM) und Zielpräparationen mittels Focused-Ion-Beam (FIB) wird dieser postulierte Mechanismus überprüft, indem die lokale Mikrostruktur um den rissauslösenden Einschluss und der Rissverlauf detailliert aufgelöst werden.

Translation: E. Engert

Patrick Grad born in 1985, studied mechanical engineering at the University of Kaiserslautern. Since 2011 he has been a scientific assistant in the Working Group of Materials Testing at the University of Kaiserslautern, Germany. His research is focused on the fatigue behaviour of high-strength steels in the VHCF-regime

Eberhard Kerscher studied physics and wrote a doctoral thesis about fatigue of high strength materials at the University of Karlsruhe. Then he was head of the department “Microstructure and Properties” and the materialography lab before he became a Professor for Materials Testing at the University of Kaiserslautern.

References / Literatur

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[4] Kerscher, E.; Lang, K.-H.; Löhe, D.: Rissausbreitung in hochfesten Stählen, in: Proc. Int. Conf. Metallography, 2008, G. Petzow (Ed.), Jena, 2008Search in Google Scholar

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Received: 2012-4-25
Accepted: 2012-6-5
Published Online: 2013-05-23
Published in Print: 2012-08-01

© 2012, Carl Hanser Verlag, München

Articles in the same Issue

  1. Contents/Inhalt
  2. Contents
  3. Editorial
  4. Editorial
  5. Technical Contributions/Fachbeiträge
  6. Analysis of the Crack Initiation at Non-Metallic Inclusions in High-Strength Steels
  7. Evaluation of Diffusion Bonding (Welding) Process Temperatures of AISI 1010 Plain Carbon Steel with AISI 430 Ferritic and AISI 420 Martensitic Stainless Steels
  8. Effect of Austempering Temperature and Time on the Kinetics and Microstructure of Austempered Compacted Graphite Cast Irons
  9. Corrosion Damage to a Dropped Handlebar Made of AA7075
  10. Meeting Diary/Veranstaltungskalender
  11. Meeting Diary
https://doi.org/10.3139/147.110190

Articles in the same Issue

  1. Contents/Inhalt
  2. Contents
  3. Editorial
  4. Editorial
  5. Technical Contributions/Fachbeiträge
  6. Analysis of the Crack Initiation at Non-Metallic Inclusions in High-Strength Steels
  7. Evaluation of Diffusion Bonding (Welding) Process Temperatures of AISI 1010 Plain Carbon Steel with AISI 430 Ferritic and AISI 420 Martensitic Stainless Steels
  8. Effect of Austempering Temperature and Time on the Kinetics and Microstructure of Austempered Compacted Graphite Cast Irons
  9. Corrosion Damage to a Dropped Handlebar Made of AA7075
  10. Meeting Diary/Veranstaltungskalender
  11. Meeting Diary
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