Title: Ductile-to-brittle transition temperature of thermally segregated WWER-1000 base metal

Authors: L. Debarberis, B. Acosta, A. Zeman, S. Pirfo, P. Moretto, A. Chernobaeva, Y. Nikolaev

Addresses: European Commission, Joint Research Centre Institute for Energy, Westerduinweg 3, 1755 LE Petten, the Netherlands. ' European Commission, Joint Research Centre Institute for Energy, Westerduinweg 3, 1755 LE Petten, the Netherlands. ' European Commission, Joint Research Centre Institute for Energy, Westerduinweg 3, 1755 LE Petten, the Netherlands. ' European Commission, Joint Research Centre Institute for Energy, Westerduinweg 3, 1755 LE Petten, the Netherlands. ' European Commission, Joint Research Centre Institute for Energy, Westerduinweg 3, 1755 LE Petten, the Netherlands. ' Russian Research Centre, Kurchatov Institute, Kurchatov Square 1, 123182 Moscow, Russia. ' Russian Research Centre, Kurchatov Institute, Kurchatov Square 1, 123182 Moscow, Russia

Abstract: A series of thermal treatments on typical WWER-1000 reactor pressure vessel steel has been carried out to induce phosphorus segregation. Two conditions have been achieved with significantly different ductile-to-brittle transition temperatures, when compared to untreated metal. Tensile properties, hardness and non-destructive techniques have also been investigated. This study confirms that when phosphorus segregation leads to embrittlement, which is directly detected by Charpy testing, owing to the non-hardening nature of the embrittlement mechanism, neither hardness nor the other applied non-destructive testing (thermoelectric, magnetic Barkhausen and positron annihilation) provide substantial indication of material degradation. The results obtained are important sources of information to understand the behaviour of materials for which phosphorus segregation might occur; in particular with regard to their sensitivity to fracture.

Keywords: reactor pressure vessel steel; thermal treatments; impurities segregation; ductile-to-brittle transition; thermoelectric properties; positron annihilation spectroscopy; PAS; pressure vessels; phosphorus segregation; heat treatment; embrittlement; fracture; NDT; hardness.

DOI: 10.1504/IJMMP.2007.015312

International Journal of Microstructure and Materials Properties, 2007 Vol.2 No.3/4, pp.326 - 338

Published online: 07 Oct 2007 *

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