Study of cracking and microstructure in Co-free valve seat hardfacing

Zaiqing Que, Matias Ahonen, Iikka Virkkunen, Pekka Nevasmaa, Paavo Rautala, Hannu Reinvall

Research output: Contribution to journalArticleScientificpeer-review

Abstract

For reducing the radiological hazard, Co-free hardfacing alternatives have been used to replace the traditional Co-based hardfacing alloys in nuclear power plant applications. However, manufacturing a defect-free Co-free hardfacing is challenging. Reduced galling resistance and mechanical properties exhibited by common replacement alloys in some conditions limit the application. This issue is important for the operating nuclear power plants with lifetime extension and also for the new builds. In this paper, a failed industrial hardfacing was studied. Through-the-thickness cracks of the Co-free hardfacing deposit with NOREM 02 on a nuclear swing check plug were detected. The potential cause of the brittle interdendritic cracking was studied and the detailed microstructure of the Co-free hardfacing analysed. The solidification defects during the manufacturing and the lacking of ferrite phase in the microstructure together with the potentially non-optimized handling procedures are concluded to be the causes of the observed cracking.

Original languageEnglish
Article number101202
JournalNuclear Materials and Energy
Volume31
DOIs
Publication statusPublished - Jun 2022
MoE publication typeA1 Journal article-refereed

Keywords

  • Cobalt-free
  • Hardfacing
  • Microstructure
  • Nuclear
  • Valve

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