Development of Tungsten/Copper Gradient Material

Abstract

A sintering and infiltration technique to manufacture functionally gradient materials has been developed. This technique consists of two steps and is suitable for manufacturing a tungsten (W) /copper (Cu) gradient material. The first step is to make a sintered tungsten with the gradient pore distribution. The second step is to infiltrate a molten copper into the pores. In this technique, capsule-free HIP (Hot Isostatic Pressing) treatment is effectively used for fully densifying the surface tungsten layer and for eliminating only closed pores in the other layers. Capsule HIP treatment is effective to fully infiltrate a molten copper into open pores of the sintered tungsten. The tungsten/copper gradient material has an excellent ability to reduce thermal stress and has good thermal conductivity from the tungsten layer to the copper. It is because of continuous microstructure change from one layer to another. The results of heating tests using electron beam irradiation equipment successfully showed that the tungsten/copper gradient materials can endure a stationary heat flux of up to 15 MW/m², which is necessary for divertor plate as a plasma facing component in the ITER (International Thermonuclear Experimental Reactor).