Benchmarking by high heat flux testing of W-steel joining technologies

0579108 - ÚFP 2024 RIV NL eng J - Journal Article
Dorow-Gerspach, D. - Bram, M. - Ganesh, V. - Matějíček, Jiří - Pintsuk, G. - Vilémová, Monika - Wirtz, M. - Linsmeier, Ch.
Benchmarking by high heat flux testing of W-steel joining technologies.
Nuclear Materials and Energy. Roč. 37, December (2023), č. článku 101508. E-ISSN 2352-1791
EU Projects: European Commission(BE) 101052200
Institutional support: RVO:61389021
Keywords : Atmospheric plasma spraying * Ductile interlayer * Functionally graded material * High heat flux benchmark test * Spark plasma sintering * W/steel joints
OECD category: Materials engineering
Impact factor: 2.6, year: 2022
Method of publishing: Open access
https://www.sciencedirect.com/science/article/pii/S2352179123001473?via%3Dihub

For a future commercial fusion reactor, the joining of tungsten and steel will be of vital importance, covering the main part of the plasma facing area. However, the large difference, of more than a factor of 2, in the coefficient of thermal expansion (CTE) of W and steel results in high thermal stresses at their interface. The cyclic nature of the operation can cause fatigue effects and could result in a premature failure of the joint. One possible solution is the insertion of a functionally graded material (FGM), with varying the CTE, as an interlayer between tungsten and steel, which could reduce these stresses. In this study, two processes, atmospheric plasma spraying (APS) and spark plasma sintering (SPS), are utilized to manufacture such FGMs. The gradation was accomplished by using two or three layers with a thickness of 0.5 mm each. Another principle is the insertion of a ductile metal interlayer, which reduces the stress by plastic deformation. Vanadium and titanium foils of varying thickness were chosen, as both have a CTE in between W and steel and V forms a solid solution with W and Fe. These and a direct W-steel joint as baseline reference were made by current-assisted diffusion bonding. All samples consist of 3 mm thick W and steel tiles allowing a direct comparison of the different technologies. An efficient high heat flux benchmark test procedure was developed and performed to investigate and compare the potential of the different joining technologies. For this, the complete stacks were brazed on actively cooled copper cooling modules and tested with high stationary heat loads of up to 5 MW/m2 with 200 cycles at each level in the JUDITH 2 facility. Detailed thermal analysis including comparison with prediction based on FEM simulation are presented to understand the cause of the failure and track the degradation. This study allows to help focusing the further development of W-steel joining technologies.
Permanent Link: https://hdl.handle.net/11104/0347975