Evaluation of an alloy 52/cladded carbon steel repair weld by cold metal transfer

Caitlin Huotilainen, Heikki Keinänen, Juha Kuutti, Pekka Nevasmaa, Henrik Sirén, Iikka Virkkunen

Tutkimustuotos: Artikkeli kirjassa/konferenssijulkaisussaConference contributionScientificvertaisarvioitu

Abstrakti

Extending the lifetime of existing nuclear power reactors is an increasingly important topic. As the existing fleet of nuclear power reactors ages and approaches the end of their design lifetimes or enters periods of lifetime extension, there is an increased probability for defect repairs due to extended exposure to the operating environment (e.g. high temperature, high pressure, corrosion environment, neutron irradiation, etc.). Concerning repair welding, should a critical need for repair arise, qualified and validated solutions must be readily available for rapid deployment. A proposed method using robotized gas metal arc welding-cold metal transfer to repair a "worst-case" scenario, linear crack like defect beneath the cladding, which extended into the reactor pressure vessel steel, was evaluated on laboratory scale in previous works (PVP2020-21233, PVP2020-21236). These previous studies demonstrated that cold metal transfer has the potential to produce high quality welds in the case of a reactor pressure repair. In the current study, the lessons learned from the previous work were applied to repair a postulated surface crack on a thermally embrittled and cladded low alloy steel plate using a nickel base Alloy 52 filler metal. Two excavations were filled using different weld bead arrangements-a traditional pattern (92 weld beads, Q = 0.6 kJ/min) and a 45°-hatch pattern (184 weld beads, Q = 0.9 kJ/min)-by gas metal arc welding-cold metal transfer. No pre-heating or post-weld heat treatment were applied, to remain in line with what can be expected in a real pressure vessel repair situation. The 0° angle pattern acts as a reference for previous studies, while the 45°-hatch pattern, aims to minimize the residual stresses caused by repair welding. Finite element modeling was used to predict the initial (cladded, embrittled and excavated) condition of the steel plate, followed by simulating the welding using the actual welding conditions and material constants for both bead patterns as input parameters. The resulting deformation, strains and stresses created in the material due to repair welding were predicted and the welding's effectiveness was estimated. In addition, the postrepair weld mechanical properties and microstructure, specifically focusing on the fusion boundary and heat-affected zone, were evaluated using various microscopy techniques and hardness measurements. The outcomes of the performed simulations, corresponding characterizations and lessons learned are presented in this study.

AlkuperäiskieliEnglanti
OtsikkoMaterials and Fabrication
KustantajaAmerican Society of Mechanical Engineers
Sivumäärä9
ISBN (elektroninen)9780791885345
DOI - pysyväislinkit
TilaJulkaistu - 18 lokak. 2021
OKM-julkaisutyyppiA4 Artikkeli konferenssijulkaisuussa
TapahtumaASME Pressure Vessels and Piping Conference - Virtual, Online
Kesto: 13 heinäk. 202115 heinäk. 2021

Julkaisusarja

NimiAmerican Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP
Vuosikerta4
ISSN (painettu)0277-027X

Conference

ConferenceASME Pressure Vessels and Piping Conference
LyhennettäPVP
KaupunkiVirtual, Online
Ajanjakso13/07/202115/07/2021

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