Design of a W/steel functionally graded material for plasma facing components of DEMO

The design of a graded transition between tungsten and steel for plasma facing components of a nuclear fusion reactor is proposed and the interest of such a transition is demonstrated by FEM calculations of the thermo-mechanical behaviour in the operating conditions of the DEMO reactor. The transition consists in stacked layers of W–WC and WC–Fe between W and Eurofer steel. The maximum surface temperature of the structural component could be maintained below 1300 °C for a very simple multilayer geometry, from FEM calculations. The maximum strains and equivalent elastic stresses could be reduced by a factor of about 3 as compared to a direct W/steel joint. Considerations about processing techniques of such a component are discussed, based on the literature background and a few preliminary tests.

► Graded transition between tungsten and steel for plasma facing components.
► Local thermodynamic equilibrium in the multilayer sequence.
► Improved thermo-mechanical properties compared to a bi-material from FEM calculations.
► Discussion of possible processing techniques via the powder metallurgy route.