Effect of TaC addition on microstructure and microhardness of additively manufactured tungsten

In this study, 5 wt% tantalum carbide (TaC) was added as a secondary component into tungsten (W) samples fabricated by laser powder bed fusion (LPBF) technique. The microstructures were investigated by SEM, EBSD, TEM, XRD and nano-indentation. With the addition of TaC, the density of cracks is significantly reduced compared to the pure W. Cellular structures, consisting of W(Ta) solid solution as base and intercellular tungsten carbides (W2C), were observed at different location with various morphologies. Hexagonal and orthorhombic W2C phases were confirmed. The intercellular W 2 C were suggested to be formed by insitu reaction in a divorced eutectic approach during LPBF process. This study provides an effective way to strengthen and refine the W microstructure by a synergistic effect of grain refinement, solid-solution, eutectic and oxygen consumption, thus providing further argument for the novel strengthening method to reduce LPBF W cracks. (C) 2021 Elsevier B.V. All rights reserved.