Development of chromium and chromium-tungsten alloy for theplasma facing components Application of vacuum arc meltingtechniques

Dmitry Terentyev, Tymofii Khvan, Jeong-Ha You, Nele Van Steenberge

    Research outputpeer-review


    Design:of plasma-facing components (PFC) for DEMO divertor unravels new challenges to be met by thein-vessel materials. Embrittlement induced by 14 MeV neutrons in the baselinefirst wall material -tungsten (W) endangers structural integrity of PFCs. Chromium (Cr) and/or CreW alloy is currentlyconsidered as a candidate material in the design of mid heatflux PFCs as structural body of themonoblock. Cr has the superior mechanical properties in the low temperature range where the com-mercial tungsten products are brittle. However, the fabrication of Cr requires high level purity controland is therefore challenging for mass production.In this work, vacuum arc melting (VAM) equipment is employed for the fabrication of chromium (Cr) andCr-10at.%W alloy targeted for the PFC applications. VAM techniques represents new promising alterna-tive route with a high upscale potential. VAM fabrication improves Cr quality by avoiding the intro-duction of interstitial impurities, while the produced ingots can be further mechanically treated as wellas solution alloyed by W to design a dedicated microstructure thus enhancing important mechanicalproperties, e.g. yield strength and fracture toughness.The produced heats of pure Cr and Cre10 W are investigated by means of chemical and microstructuralanalysis as well as by mechanical testing. The obtained results are compared with those obtained forpure Cr and W products fabricated by Plansee (Austria). The VAM-produced pure Cr (without anythermo-mechanical optimization) shows the transition to ductility deformation mode just above theroom temperature proving the principal advantage of this fabrication route. Solid solution with 10% of Wsignificantly improves the proof stress while sustaining good ductility at elevated temperatures. Theductile to brittle transition in Cre10%W is observed around 300C, which likely can be reduced further by thermo-mechanical treatment. The bending strength of the tested pure Cr grades is considerablylower than that of pure tungsten, when compared at the technologically relevant temperature i.e. 300-500C. Whereas the bending strength of Cre10%W constituted about 80% of the strength of puretungsten. Hence, the developed VAM Cr and CreW alloys require a next step assessment with respect toneutron irradiation testing and improvement by thermo-mechanical treatment.
    Original languageEnglish
    Article number152240
    Pages (from-to)1-11
    Number of pages11
    JournalJournal of Nuclear Materials
    StatePublished - 5 May 2020

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