Effect of Thermal Ageing and Microstructure on Fracture Mechanical Behaviour of Ni-based Alloy Dissimilar Metal Welds
Zaiqing Que, Sebastian Lindqvist, Noora Hytönen, Yanling Ge, Kristina Lindgren, Mattias Thuvander, Pål Efsing,
DMWs are commonly used to join austenitic and ferritic components in the RCPB and can become potential concerns regarding the structural integrity of the nuclear power SSC. In particular, the knowledge on the local strength mismatch at the LAS/nickel-based alloy weld metal interface upon PWHT and during long-term ageing is lacking. The amount of information available in the open literature on the fracture mechanical and microstructural changes occurring at the fusion boundary after buttering, welding, PWHT and long-term ageing is relative limited and often very case dependent. Understanding the fracture mechanical and microstructural appearance, behaviour and development of the complex DMW fusion boundary is crucial for both the improvement of nuclear component integrity and to ensure safe long-term operation. In this study, a Ringhals SA508/Alloy52 DMW mock-up consisting of Alloy 52 buttering on both sides (representative of Ringhals 3 pressurizer surge nozzle DMW) and a TVO NG DMW mock-up are studied, thus the test materials are representative of actual power plant components. The project promotes the knowledge transfer, improve the nuclear materials and fracture mechanics competence and strengthen the connections and experience exchange between the Nordic research organizations, universities, industries, authorities, and especially the young generation. The project deals with the structural integrity, long-term operation, and ageing management, which are relevant for both present and future nuclear power plants. The technical results provide a basis for assessment of long-term operation for the Finnish and Swedish nuclear power plants for both the operators and the regulatory perspectives. Dissemination through the open seminar, the peer reviewed publications and the oral presentations at the international conferences ensured the knowledge exchange in international and Nordic networks.
Dissimilar metal weld, Alloy 52, fusion boundary, characterisation, fracture mechanical test