Microstructural Characterization of Alloy 52 Narrow-Gap Dissimilar Metal Weld After Aging

  • Teemu SarikkaEmail author
  • Roman Mouginot
  • Matias Ahonen
  • Sebastian Lindqvist
  • Ulla Ehrnstén
  • Pekka Nevasmaa
  • Hannu Hänninen
Conference paper
Part of the The Minerals, Metals & Materials Series book series (MMMS)


The safe-end dissimilar metal weld (DMW) joining the reactor pressure vessel to the main coolant piping is one of the most critical DMWs in a nuclear power plant (NPP). DMWs have varying microstructures at a short distance across the ferritic-austenitic fusion boundary (FB) region. This microstructural variation affects the mechanical properties and fracture behavior and may evolve as a result of thermal aging during long-term operation of an NPP. This paper presents microstructural characterization performed for as-manufactured and 5000 h and 10,000 h thermally aged narrow-gap DMW representing a safe-end DMW of a modern pressurized water reactor (PWR) NPP. The most significant result of the study is that the thermal aging leads to a significant decrease in a hardness gradient observed across the ferritic-austenitic FB of the as-manufactured DMW.


Dissimilar metal weld Ni-base alloy Microstructural characterization Aging 



This study, carried out in parallel with that presented by Ahonen et al. on mechanical behavior, has been made in collaboration between Aalto University School of Engineering and VTT Technical Research Centre of Finland Ltd within the Nickel-base Alloy Welding Forum (NIWEL)-research project funded by TEKES, Finnish (Teollisuuden Voima Oyj and Fortum Oyj) and Swedish (Vattenfall AB and OKG AB) energy industry. The authors wish to express their gratitude for the funding and participation to the project.


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Copyright information

© The Minerals, Metals & Materials Society 2019

Authors and Affiliations

  • Teemu Sarikka
    • 1
    Email author
  • Roman Mouginot
    • 1
  • Matias Ahonen
    • 2
  • Sebastian Lindqvist
    • 2
  • Ulla Ehrnstén
    • 2
  • Pekka Nevasmaa
    • 2
  • Hannu Hänninen
    • 1
  1. 1.Aalto University School of EngineeringAaltoFinland
  2. 2.VTT Technical Research Centre of Finland Ltd, VTTEspooFinland

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