Additive Manufacture of Tungsten Armored Plasma Facing Components

Tungsten and its alloys are candidates for plasma facing component (PFC) armor due to their low sputtering rate, high melting point, high thermal conductivity, high strength at elevated temperatures, and low tritium inventory. Although copper alloys have been selected for the heat sinks for ITER, a working fusion reactor will require the use of higher strength, low activation materials. For example, ITER neutron fluence estimates for structural components are 0.3MWa/m2, which corresponds to a 3dpa. In contrast, the neutron fluence in a demonstration reactor will exceed 10-15 MWa/m2 or 100-150dpa. Therefore, low activation structural materials such as reduced activation ferritic/martensitic (RAFM) steels will be needed. A pre-conceptual power plant such as the ARIES-ACT1 will require a tungsten armored-RAFM steel first wall, which will correspond to 75-80% of the plasma facing surface. Therefore, techniques for joining tungsten armor to RAFM steel substrates are needed. During this effort, additive manufacturing techniques will be developed to allow joining of low coefficient of thermal expansion (CTE) tungsten armor to high CTE RAFM steels using functional gradient materials (FGMs). Thus, a three dimensional joint will be produced and the thermal induced stresses will not be concentrated at a planar bond line. To produce the FGM joints during the Phase I investigation, two additive manufacturing methods will be evaluated: Vacuum Plasma Spray (VPS) and High Pressure Cold Spray (HPCS). During Phase II, the use of other additive manufacturing techniques such as laser/e-beam powder bed processing will be evaluated to enable the production of unique cooling features in the RAFM heat sink. Commercial Applications and Other Benefits In addition to joining other armor materials using additively produced functional gradient materials, commercial applications that will benefit from the technology to be developed include aerospace, defense, propulsion, power generation, semiconductor, crucibles, heat shields, x-ray targets, wear and corrosion protection coatings. Key Words: plasma facing components, PFCs, fusion, joining, tungsten, RAFM steel, additive manufacturing, cold spray, vacuum plasma spray, functional gradient materials