Correlation of creep strength and microstructural evolution of a boron alloyed 9Cr3W3CoVNb steel in as-received and welded condition

Peter Mayr, Francisca Mendez Martin, Mihaela Albu, Horst-Hannes Cerjak

Research output: Chapter in Book/Report/Conference proceedingConference paperpeer-review

Abstract

Creep strength of 9 % chromium steels is strongly coupled with the formation and interaction of different precipitate populations like MX (Nb,V)(C,N), M 23 C6 , laves phase and modified Z-phase. Changes in microstructure can be correlated to a change in creep strength. Within this work, a boron-nitrogen balanced 9Cr3W3CoVNb steel is investigated in normalised and tempered (as-received), creep exposed and welded condition. Microstructural haracterisation of normalised and tempered (as-received) and creep exposed samples have been carried out by elemental mapping techniques in transmission electron microscopy (TEM). The creep strength of the base material has been evaluated at 650°C up to a current testing duration of 17.000 hours. First testing results after 10.000 hours show a benefit in strength of the
new grade of about 40 MPa compared to conventional steel grade P92 and 60 MPa to grade P91. The results of the microstructural investigation show only very little changes of the microstructure after 10.000h of creep exposure. The investigations imply a higher microstructural stability of the new steel, compared to other 9% chromium steels.
In welded condition, the steel shows unique formation of its heat-affected zone. Although the steel experiences several phase transformations during the weld thermal cycle, the original base material microstructure is almost maintained in the heat-affected zone. The formation of a homogeneous grain refined region is suppressed and, therefore, less susceptibility to Type IV cracking is expected. Creep tests of crossweld specimens at 650°C and various stress levels are carried out to investigate the susceptibility to Type IV cracking.
Original languageEnglish
Title of host publicationCreep and Fracture in High Temperature Components - Design & Life Assessment Issues
Place of PublicationLancaster, Pa
PublisherDEStech Publications, Inc
Pages1029-1037
ISBN (Print)978-1-60595-005-1
Publication statusPublished - 2009
Event2009 ECCC International Conference on Creep and Fracture in High Temperature Components: Design & Life Assessment Issues - Zurich, Switzerland
Duration: 21 Apr 200923 Apr 2009

Conference

Conference2009 ECCC International Conference on Creep and Fracture in High Temperature Components: Design & Life Assessment Issues
Abbreviated titleECCC Creep Conference 2009
Country/TerritorySwitzerland
CityZurich
Period21/04/0923/04/09

Treatment code (Nähere Zuordnung)

  • Basic - Fundamental (Grundlagenforschung)

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  • Materials Development

    Dikovits, M. (Co-Investigator (CoI)), Sommitsch, C. (Co-Investigator (CoI)), Caliskanoglu, O. (Co-Investigator (CoI)), Schlacher, C. (Co-Investigator (CoI)), Beal, C. (Co-Investigator (CoI)), Djuric, D. (Co-Investigator (CoI)), Vujic, S. (Co-Investigator (CoI)), Pein, C. (Co-Investigator (CoI)), Krumphals, F. (Co-Investigator (CoI)), Kuduzovic, A. (Co-Investigator (CoI)) & Halici, D. (Co-Investigator (CoI))

    1/03/0931/12/24

    Project: Research area

  • Nanoanalysis using transmission electron microscopy

    1/01/0431/12/24

    Project: Research area

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