Grain Boundary Phosphorous Segregation and Its Influence on the Ductile Brittle Transition Temperature in Reactor Pressure Vessel Steels

    Volume 1, Issue 9 (October 2004)

    ISSN: 1546-962X

    CODEN: JAIOAD

    Published Online: 4 October 2004

    Page Count: 14


    Kimura, A
    Professor, Graduate Student, and Research Associate, IAE, Kyoto University, Gokasho, Uji, Kyoto,

    Shibata, M
    Professor, Graduate Student, and Research Associate, IAE, Kyoto University, Gokasho, Uji, Kyoto,

    Kasada, R
    Professor, Graduate Student, and Research Associate, IAE, Kyoto University, Gokasho, Uji, Kyoto,

    Nakata, H
    Senior Researcher, Institute of Nuclear Safety System, Inc., Mihama, Mikata, Fukui,

    Fujii, K
    Senior Researcher, Institute of Nuclear Safety System, Inc., Mihama, Mikata, Fukui,

    Fukuya, K
    Senior Researcher, Institute of Nuclear Safety System, Inc., Mihama, Mikata, Fukui,

    (Received 14 October 2002; accepted 14 October 2003)

    Abstract

    The materials used for this work were two sorts of reactor pressure vessel (RPV) steels, which contain different amounts of phosphorous (P), namely 0.011 and 0.002 wt%. The specimens for Charpy V-notch (CVN) impact test, Auger electron spectroscopy (AES), and tensile test were thermally aged at 400, 450, and 500°C for 1000, 3000, and 5000 h. After the thermal aging, the AES specimens were broken in the AES chamber to measure the P concentration at grain boundaries. The AES measurements for as-received specimens were carried out following hydrogen charging so that grain boundary facets were available even without P segregation. The AES measurements revealed that the peak height ratio (PHR) of P/Fe at the grain boundaries of the high-P steel were 0.066, 0.141, and 0.120 in the specimens aged at 400°C for 3000 h, 450°C for 3000 h, and 500°C for 1000 h, respectively. The ductile-brittle transition temperature (DBTT) was measured for the aged specimens, and the ΔDBTT of 15K was observed only for the specimen aged at 450°C for 3000 h, although no changes in the hardness and tensile properties were observed. The grain boundary fracture ratio (GBFR) increased with increasing the PHR of P/Fe. Grain boundary fracture mode was located at the area close to the V-notch root. There was a good relationship among PHR, GBFR, and DBTT, indicating directly that the shift in the DBTT was due to grain boundary embrittlement caused by P segregation.


    Paper ID: JAI11369

    DOI: 10.1520/JAI11369

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    Author
    Title Grain Boundary Phosphorous Segregation and Its Influence on the Ductile Brittle Transition Temperature in Reactor Pressure Vessel Steels
    Symposium The Effects of Radiation on Materials: 21st International Symposium, 2002-06-20
    Committee E10