Advances in nuclear fusion reactors core architecture have led to consider metallic additive manufacturing (AM) as one of the prime manufacturing processes, especially for components with highly complex internal structures such as the breeding blanket and divertor. Depending on the size and shape, Laser Powder Bed Fusion (LPBF) or Laser Directed Energy Deposition (L-DED) processes are envisioned to produce these parts.
Among proposed Plasma Facing Components (PFCs) materials, tungsten is the leading first-wall armor candidate to cover and shield the structural Reduced-Activation Ferritic-Martensitic (RAFM) steel components of the reactor core. Ideally, these materials are directly bonded together as one component with integrated cooling channels. However, joining those two very dissimilar materials using laser AM poses a serious, multifaceted challenge, considering their highly different processing parameters. Multimodal characterization using both well-established ex-situ techniques and novel operando techniques at synchrotron light sources and neutron sources allows gaining profound insights into the process dynamics of producing tungsten cladded RAFM steel components and multi-material AM components in general.
Bi-layered specimens of tungsten on RAFM were printed using LPBF and L-DED; formation of intermetallic phases at the interface was observed and characterized using various operando (XRD) and ex-situ (EBSD, µXRD, µXRF and neutron imaging) techniques, and the resulting stress/strain field was measured using Neutron Bragg-edge imaging. Unexpected microstructural patterns have been observed in the bulk steel phase and characterized using the same methods. Cross-correlated results obtained from conventional, synchrotron and neutron techniques are presented and demonstrated to be a very powerful way of getting profound insights on unexpected process-driven mechanisms in metallic additive manufacturing.