G. Pintsuk (Sp), J.-E. Döring, J. Linke, Forschungszentrum-Jülich (Germany)
The joining of tungsten and copper is one of the challenging issues in the field of composite materials. The reason why this material combination is of essential importance is its ability to withstand high temperatures on the tungsten side and to remove big quantities of heat on the copper side. The concept deals with functionally graded structures of W and Cu; these two metals exhibit extreme differences in material properties, but are free from mutual chemical interactions. Due to the mismatch of thermal expansion coefficients and Young’s moduli, the joining of these two materials can result in high residual and thermal stresses at the interface, ultimately reducing component lifetime.
The focus within the present study is set on components in nuclear fusion devices, especially in the divertor-region, where stationary heat fluxes up to 20 MW/m2 have to be dissipated. For the fabrication of the computationally optimized functionally graded material (FGM), Vacuum Plasma Spraying (VPS) is chosen as state-of-the-art production process. The FGM is integrated into a HIP-bonded, actively cooled W/Cu-module based on the flat-tile concept. Stationary heat fluxes up to 23.8 MW/m2 and cyclic thermal loads up to 20 MW/m2 were applied in the electron beam testing facility JUDITH. Differences in the performance depending on the castellation of the W-surface are outlined and failure criteria discussed.