Effect of weld microstructure on brittle fracture initiation in the thermally-aged boiling water reactor pressure vessel head weld metal

Abstract Effects of the weld microstructure and inclusions on brittle fracture initiation are investigated in a thermally aged ferritic high-nickel reactor pressure vessel head from decommissioned nuclear power plant. As-welded reheated regions mainly consist acicular polygonal ferrite, respectively. Fractographic examination Charpy V-notch impact toughness specimens reveals large (0.5–2.5 µm) at primary sites. High energies were measured for which was initiated small inclusion or an away V-notch. The density, geometry, chemical composition investigated. A crack initiates as microcrack either within multiphase oxide de-bonded interfaces between uncracked metal matrix. Primary sites can be determined all tested lower part transition curve below 41-J reference energy but not above mentioned value because changes mechanism resulting appearance.