Argon-seeded plasma exposure and oxidation performance of tungsten-chromium-yttrium smart alloys

Tungsten-chromium-yttrium(WCrY)smart alloys are foreseen as the first wall material for future fusion devices such as Demonstration Power Plant(DEMO).While suppressing W oxidation during accidental conditions,they should behave like pure W during plasma operation due to preferential sputtering of the lighter alloying elements Cr,Y,and W enrichment of the surface.In this paper,the erosion performance of WCrY and W samples simultaneously exposed to deuterium(D)plasma with the addition of 1%of the projectile ions being argon(Ar)ions at an ion energy of 120 eV is compared.With reference to the previous experiments at 120 eV in pure D plasma,the erosion for both WCrY and W is enhanced by a factor of~7.Adding Ar to the D plasma suppresses significant W enrichment previously found for pure D plasma.To investigate the impact of the plasma exposure onto the oxidation performance,plasma-exposed and non-exposed reference samples were oxidised in a dry atmosphere.Results show,on the one hand,that the oxida-tion suppression of WCrY in comparison to pure W is preserved during the plasma performance.On the other hand,it becomes evident that edge effects imposed by the geometry of the samples used in plasma experiments play a significant role for the oxidation behaviour.