High Temperature Electron Beam Additive Manufacturing of Tungsten Plasma Facing Components with Integrated Porous Armor

Cost-effective materials and manufacturing are crucial towards realization of many largescale human endeavors including space exploration and understanding the origins of the Big Bang. For grid-scale fusion, robust divertors with a large heat removal capability, robust mechanical properties, low sputtering yield and transient plasma damage tolerance must be developed. Scalable production methods are also needed, as these parts will need to be replaced during a fusion plant lifetime. Additive manufacturing (AM) is rapidly changing the way heat transfer devices are designed and manufactured, reducing complex assemblies to monolithic structures. Plasma-facing AM tungsten lattices with location-specific design features could act as thermal shock absorbers, alleviating some of the concerns regarding plasma transients on fusion divertors. AM-enabled heat exchange enhancing features can also be included on the internals of the component. We propose to print a solid, near-net shape, pure W thimble with a metallurgically bonded lattice armor using Electron Beam Powder Bed Fusion (EB-PBF) onto a vanadium substrate. The combination of high power beam, vacuum processing and controlled heating/cooling are well suited to printing clean, crack-free tungsten. After post-print finishing, the composite tungsten/vanadium component can be vacuum brazed at a reduced activation steel distribution manifolds. We demonstrated the ability to print full-density (99.9%), centimeters scale tungsten solids and lattices. Our material demonstrates high temperature ductility during 4-point bending and near-equiaxed microstructure. We upgraded the newest generation electron beam printer to include a tungsten-specific modular print tank, specialized powder hoppers and multi-layer radiation shielding. We also performed post-processing including machining and electropolishing of the AM tungsten, as well as vacuum brazing. We published 2 peerreviewed journal articles outlining our print process as well as plasma material interaction testing at UCSD. Phase II-B will focus on development of scalable, assembly-level additively manufactured tungsten HEMJ components with associated machining, joining, NDE, plasma material interaction and HHF testing. Specific focus will be placed on tailoring the lattice design parameters and the EB printing process to achieve fine detail lattice features. Another key feature for assembly level development is a metallurgical joining strategy for joining W to reduced activation (RA) steel as well as optimization of the internal cooling structure. Testing will include mechanical metrology, hydraulic pressure testing, metallographic examination and x-ray computed tomography. Batch production of tungsten fusion components using additive manufacturing could simplify fabrication while enabling more complex power plant architectures. Similarly, printing tungsten heat transfer components with integrated cooling could have significant applications in other fields such as medical imaging, radiation oncology and hypersonic vehicles.