Improved pseudo-ductile behavior of powder metallurgical tungsten short fiber-reinforced tungsten (Wf/W). (May 2018)

• Record Type: Journal Article
• Authors: Coenen, J.W.; Mao, Y.; Sistla, S.; Riesch, J.; Hoeschen, T.; Broeckmann, Ch.; Neu, R.; Linsmeier, Ch.
• Is Part Of: Nuclear materials and energy. Volume 15(2018)
• Page Start: 214
• Page End: 219
• Publication Date: 2018-05
• Subjects: Nuclear energy -- Periodicals; Nuclear fuels -- Periodicals; Nuclear reactors -- Materials -- Periodicals; Radioactive substances -- Periodicals; 621.4833
• DOI: 10.1016/j.nme.2018.05.001
• Languages: English
• ISSNs: 2352-1791

Abstract

Highlights: Based on the presented tests for PM- Wf / W with W-foil it can be said that the manufacturing path for Wf / W has been further improved. The presented approach utilising a W-Foil mitigates the embrittlement of the constituent fibres during FAST processing. Based on these results it can be seen that improved pseudo-ductile behaviour can be achieved for PM- Wf / W . It is planned to utilise this new route in developing prototype components for applicationin existing fusion devices. In order to also establish material performance under irradiation PM - Wf / W samples are earmarked for irradiation in a nuclear reactor starting in 2018. Abstract: For the first wall of a fusion reactor unique challenges on materials in extreme environments require advanced features in areas ranging from mechanical strength to thermal properties. The main challenges include wall lifetime, erosion, fuel management and overall safety. For the lifetime of the wall material, considerations of thermal fatigue due to transient heat loading are crucial as severe mechanical and thermal loads during operation are expected. Tungsten (W) is the main candidate material for the first wall of a fusion reactor as it is resilient against erosion, has the highest melting point of any metal and shows rather benign transmutation behavior under neutron irradiation. However, Tungsten has an issue related to intrinsic brittleness as well as operational embrittlement. To overcome this, a W-fiber enhanced W-composite material ( Wf / W ) incorporating extrinsic toughening mechanisms has been developed. Recently progress has been made in the powder metallurgical routes towards fully dense multi short-fiber Wf / W . For reasonable performance with respect to mechanical properties and hydrogen retention a fully dense pseudo-ductile Wf / W with is crucial. The properties of the used fibres are crucial. For the composite mechanisms to work a level of strength of the used fibres is required. In this contribution the change in ductility of the fibres is studied. In this contribution it is shown that excluding or minimising the impact of carbon impurities during the sintering process can significantly improve the mechanical properties of the fibres. New test results on the behaviour of PM Wf / W with and without a diffusion barrier during the sintering show a clear benefit as the fibres can retain ductility. Not the grain growth during sintering but the carbon present during sintering is clearly identified as determining the mechanical properties of the fibres.