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This work has been carried out within the framework of the EURO-fusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200 - EUROfusion) . Views and opinions expressed are however those of the author (s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them.

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HHF response of an optimized W-EUROFER joint brazed with pure copper

Publicado en:Materials Characterization. 219 114621- - 2025-01-01 219(), DOI: 10.1016/j.matchar.2024.114621

Autores: Izaguirre, I; Dorow-Gerspach, D; de Prado, J; Sanchez, M; Wirtz, M; Urena, A

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Resumen

The optimization of joint microstructure plays a critical role in assessing joint performance under high heat flux (HHF) conditions, as it dictates the final properties of the joint. This study investigates tungsten-EUROFER joints brazed using a copper interlayer as filler material under optimized brazing cycle conditions (1110 degrees C, 3 min), and subjected to simulated high heat fluxes exposing the plasma facing material, tungsten in this case, to a heating source (accelerated electron bean), while the joint is refrigerated through the EUROFER side. This experiment aims to mimic the heat fluxes and cooling conditions experienced in a fusion reactor environment. An optimized microstructure of the braze joint, designed to mitigate the formation of intermetallic compounds and undesirable phases, was implemented to enhance joint responses under high heat flux loads. The joints were subjected to 100 and 1000 heating-cooling cycles of 10/12 s. The target during heating is to reach the thermal equilibrium. Three different tungsten surface temperature were evaluated (600 degrees C, 700 degrees C and 800 degrees C) in different sample batches while cooling on the EUROFER side, removing the heat source during the cooling stage. Some overheating events, associated with crack propagation through the EUROFER-braze interface identified during the subsequent postmortem analysis by SEM, were detected during the application of some conditions of the test. The microstructure examination also reported a modification of the failure mechanism of the joint comparing with the previous studies and literature. This modification is associated with the optimized microstructure resulting in improved response to high heat flux loads. Interestingly, the shear strength increased to an average of 95.0 MPa after HHF testing, compared to 40.2 MPa obtained in similar joints with different microstructures.

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