Hannover 2016 – scientific programme

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P: Fachverband Plasmaphysik

P 13: Plasma Wall Interactions

P 13.3: Talk

Wednesday, March 2, 2016, 11:45–12:00, b302

Studies on Yttrium-Containing Smart Alloys — •Felix Klein¹, Tobias Wegener¹, Andrey Litnovsky¹, Marcin Rasinski¹, Joachim Mayer², and Christian Linsmeier¹ — ¹Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung - Plasmaphysik — ²Ernst Ruska-Centrum, 52425 Jülich

Tungsten is the main candidate as plasma-facing armour material for future fusion reactors, like DEMO. Advantages of tungsten include high melting point, high thermal conductivity, low tritium retention, and low erosion yield. A problem is oxide volatilisation under accidental conditions where the temperature of the first wall can reach 1200 K to 1450 K and air ingress occurs. Therefore smart tungsten alloys are developed. Smart alloys are supposed to preserve properties of tungsten during plasma operation coupled with suppressed tungsten oxide formation in case of an accident. Lab-scale tungsten-chromium-yttrium (W-Cr-Y) samples prepared by magnetron sputtering are used as model system. The mechanisms of oxidation and its dynamics are studied using a thermogravimetric system, focussed ion beam, and electron microscopy. A composition scan was conducted: The new material composition featuring W, ∼ 12 wt. % Cr, ∼ 0.3 wt. % Y showed strongest suppression of oxidation, no pores, and least internal oxidation. At 1273 K in argon-oxygen atmosphere an oxidation rate of 3· 10⁻⁶ mg²cm⁻⁴s⁻¹ was measured. At 1473 K ternary W-Cr-Y alloys suppressed evaporation up to 20 min while for W-Cr evaporation was already evident after 5 min. Comparison of passivation in dry and humid atmosphere, at temperatures of 1073 K to 1473 K is performed.