PSI - Issue 23

Available online at www.sciencedirect.com Available online at www.sciencedirect.com

ScienceDirect ScienceDirect

Available online at www.sciencedirect.com Structural Integrity Procedia 00 (2019) 000 – 000 Structural Integrity Procedia 00 (2019) 000 – 000

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 23 (2019) 517–522

© 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the ICMSMF organizers © 201 9 The Authors. Published by Elsevier B.V This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the IC MSMF organizers. High-loaded tempered steels, being used in mobility, power ge eration and plant engineering, are frequently exposed to very high numbers of loading cycles (up to 1 billion cycles). Optimization and fatigue testing for su h conditions is challenging and difficult, since damage i concentrated to very small area of local cyclic plasticity. The conc tration can be attributed to m terial inhomogeneiti s, such as segregations, large grains and non-me allic inclusion . The present paper demo st ates how the fatigue strength can be corr lated with the material microstructur for two tempere steels, 50CrMo4 and 16MnCr7 7, respectively, in differ nt heat-treatment conditions. This was shown by means of (i)i -situ damage observation during ultrasonic and resonance fatigue testing using light and scanning electron m croscopy (SEM) in c mbi ation with high-resolution thermogr phy, and (ii) quantitative analysis of inter al VHCF crack initiation and the formation of fine granular areas (FGA) within the fracture surface using focused ion beam milling (FIB). © 201 9 The Authors. Published by Elsevier B.V This is an open acces article under CC BY-NC-ND lic nse (http://creativecommon org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the IC MSMF organizers. 9th International Conference on Materials Structure and Micromechanics of Fracture The significance of grain size, segregations and inclusions for the very high cycle fatigue (VHCF) behavior of tempered martensitic steels Ulrich Krupp a *, Kevin Koschella b , Alexander Giertler b a IEHK Steel Institute, RWTH Aachen University, Intzestr. 1, Aachen, 52072, Germany b Institute of Materials Design and Structural Integrity, University of Applie d Sciences Osnabrück, Albrechtstr. 30, Osnabrück, 49076, Germany 9th International Conference on Materials Structure and Micromechanics of Fracture The significance of grain size, segregations and inclusions for the very high cycle fatigue (VHCF) behavior of tempered martensitic steels Ulrich Krupp a *, Kevin Koschella b , Alexander Giertler b a IEHK Steel Institute, RWTH Aachen University, Intzestr. 1, Aachen 52072, Ge many b Institute of Materials Design and Structural Integrity, University of Applie d Sciences Osnabrück, Albrechtstr. 30, Osnabrück, 49076, Germany Abstract Abstract High-loaded tempered steels, being used in mobility, power generation and plant engineering, are frequently exposed to very high numbers of loading cycles (up to 1 billion cycles). Optimization and fatigue testing for such conditions is challenging and difficult, since damage is concentrated to very small areas of local cyclic plasticity. The concentration can be attributed to material inhomogeneities, such as segregations, large grains and non-metallic inclusions. The present paper demonstrates how the fatigue strength can be correlated with the material microstructure for two tempered steels, 50CrMo4 and 16MnCr7 7, respectively, in different heat-treatment conditions. This was shown by means of (i)in-situ damage observation during ultrasonic and resonance fatigue testing using light and scanning electron microscopy (SEM) in combination with high-resolution thermography, and (ii) quantitative analysis of internal VHCF crack initiation and the formation of fine granular areas (FGA) within the fracture surface using focused ion beam milling (FIB).

Keywords: martensitic steel; VHCF; fatigue crack initiation Keywords: martensitic steel; VHCF; fatigue crack initiation

* Corresponding author. tel.: +49 241 80 92913; fax: +49 241 80 92224. E-mail address: krupp@iehk.rwth-aachen.de * Correspon ing author. tel.: +49 241 80 92913; fax: +49 241 80 92224. E-mail address: krupp@iehk.rwth-aachen.de

2452-3216 © 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the IC MSMF organizers. 2452-3216 © 2019 The Authors. Published by Elsevier B.V. This is an ope acces article under CC BY-NC-ND lic nse (http://creativecommon org/licenses/by-nc-nd/4.0/)

Peer-review under responsibility of the scientific committee of the IC MSMF organizers.

2452-3216 © 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the ICMSMF organizers 10.1016/j.prostr.2020.01.138