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Electromagnetic characterization of thermo-mechanical ageing of WB 36 steel

: Szielasko, Klaus; Altpeter, Iris; Dobmann, Gerd; Ruoff, H.; Willer, D.

Fulltext urn:nbn:de:0011-n-1781026 (1.0 MByte PDF)
MD5 Fingerprint: 7fc79ec18956f09c5708132ddd45d7cf
Created on: 25.8.2011

Deutsche Gesellschaft für Zerstörungsfreie Prüfung e.V. -DGZfP-, Berlin:
8th International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurised Components 2010. CD-ROM : Berlin, Germany, from 29th of September to 1st of October 2010
Berlin, 2011 (DGZfP Proceedings BB 125)
Paper Fr.2.C.1, 9 pp.
International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurised Components <8, 2010, Berlin>
Conference Paper, Electronic Publication
Fraunhofer IZFP ()
electromagnetic characterization; material ageing

The heat-resistant, copper-alloyed ferritic structural steel 15NiCuMoNb5 (WB 36, material number 1.6368) is widely used in German nuclear and conventional power plants. Within the framework of the federal reactor safety research program, the aging of WB 36 under the superimposed influence of both heat and cyclic deformation was characterized in close collaboration between IZFP and MPA. The goal of this investigation was to find solutions to nondestructively assess both embrittlement and fatigue in this material and to better understand their mutual interaction. In order to simulate the practical load situation in an accelerated manner, samples of different initial state were exposed to low cycle fatigue (LCF) at temperatures between RT and 350 °C. In this case, both embrittlement (caused by additional Cu precipitation) and fatigue (caused by the cyclic deformation) contribute to the aging of the material. The samples were electromagnetically characterized at IZFP, and the results were correlated to those obtained by MPA. In addition, the role of dynamic strain aging (DSA) in this process was closely examined. As a result of this project, the difference between the influences of embrittlement and fatigue in the electromagnetic testing quantities was found and described. Based on the recorded data, electromagnetic lifetime diagrams were created, showing the material degradation as a function of the number of load cycles. Moreover, MPA was able to increase the knowledge on embrittlement and fatigue processes in WB 36, and the role of DSA was found to be minor as compared to the influence of Cu precipitation.