Abstract
Effects of the weld microstructure and inclusions on brittle fracture initiation are investigated in a thermally aged ferritic high-nickel weld of a reactor pressure vessel head from a decommissioned nuclear power plant. As-welded and reheated regions mainly consist of acicular and polygonal ferrite, respectively. Fractographic examination of Charpy V-notch impact toughness specimens reveals large inclusions (0.5–2.5 µm) at the brittle fracture primary initiation sites. High impact energies were measured for the specimens in which brittle fracture was initiated from a small inclusion or an inclusion away from the V-notch. The density, geometry, and chemical composition of the primary initiation inclusions were investigated. A brittle fracture crack initiates as a microcrack either within the multiphase oxide inclusions or from the de-bonded interfaces between the uncracked inclusions and weld metal matrix. Primary fracture sites can be determined in all the specimens tested in the lower part of the transition curve at and below the 41-J reference impact toughness energy but not above the mentioned value because of the changes in the fracture mechanism and resulting changes in the fracture appearance.
| Original language | English |
|---|---|
| Pages (from-to) | 867-876 |
| Journal | International Journal of Minerals, Metallurgy and Materials |
| Volume | 28 |
| Issue number | 5 |
| DOIs | |
| Publication status | Published - 16 May 2021 |
| MoE publication type | A1 Journal article-refereed |
Funding
The authors gratefully acknowledge the BREDA program (Barsebäck Research and Development Arena) for providing the research material and the SAFIR2022 BRUTE project (Barsebäck RPV material used for true evaluation of embrittlement) for funding the study.
Keywords
- brittle fracture
- reactor pressure vessel
- thermal aging
- weld microstructure