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Localised creep cavitation on boron nitride in the heat affected zone of 9% Cr tempered martensitic steel welds

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journal contribution
posted on 16.10.2020 by Xu Xu, JA Siefert, JD Parker, Rachel Thomson
© 2020 An excessive concentration of boron in the 9% Cr tempered martensitic steels alloyed with nitrogen has a detrimental effect on creep performance, as relatively large boron nitride phases are formed and can act as the preferred sites for cavity nucleation. In the current research, a systematic investigation has been performed documenting details of creep damage in the heat affected zone of a weld joint constructed by using a 9% Cr Grade 92 steel. A combination of correlative characterisation techniques has been applied to monitor and quantify the evolution of creep damage within the heat affected zone through the entire creep life. The utilisation of cryo-fractography, two-dimensional electron-based microscopic characterisation and three-dimensional tomography based on focused ion beam microscopy have confirmed the close association between creep cavities and boron nitride phases from the initial stage of creep. It is revealed that the thermal transients imposed during welding result in the decohesion at the interface of boron nitrides with the surrounding matrix. This decohesion is a result of significant thermo-mechanical mismatch between boron nitrides and the tempered martensitic matrix. The voids initiated at these locations grow and eventually link-up during creep exposure, leading to cracking and fracture.

Funding

Electric Power Research Institute, Palo Alto, California, USA.

History

School

  • Aeronautical, Automotive, Chemical and Materials Engineering

Department

  • Materials

Published in

Materials and Design

Volume

196

Publisher

Elsevier

Version

VoR (Version of Record)

Rights holder

© The authors

Publisher statement

This is an Open Access Article. It is published by Elsevier under the Creative Commons Attribution 4.0 Unported Licence (CC BY). Full details of this licence are available at: http://creativecommons.org/licenses/by/4.0/

Acceptance date

05/08/2020

Publication date

2020-08-07

Copyright date

2020

ISSN

0264-1275

eISSN

1873-4197

Language

en

Depositor

Prof Rachel Thomson. Deposit date: 14 October 2020

Article number

109046

Licence

Exports