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 have been 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 is produced and the thermal induced stresses are not concentrated at a planar bond line. Using these techniques, subscale tungsten armored steel mockups have been produced during Phase I. During Phase II, the FGMs and substrate geometries will be optimized to remove 1-5 MW/m2 heat flux. In addition, the use of powder bed additive manufacturing techniques will be developed to produce PFC heat sinks with enhanced cooling features. Therefore, the overall goal of the Phase II investigation will be the development of an additively manufactured W armored PFC to improve fusion reactor performance. 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.