Electron Beam Powder Bed Fusion Additive Manufacturing of Refractory Metals

The processing of refractory metals via additive manufacturing (AM) presents an opportunity to fabricate components not possible through traditional powder metallurgy techniques. However, processing via AM is extremely challenging and there exist a host of technological limitations still unaddressed. Molybdenum and tungsten are two materials of particular interest for nuclear energy generation applications. The majority of existing work on the processing of these materials is focused on laser powder bed fusion whereas a smaller body of work exists for electron beam melting AM. In general, material with acceptable density can be obtained via both routes however cracking is much more difficult to mitigate against. Strong crystallographic fiber textures have been observed across a range of refractory systems. In this work we present our recent findings on electron beam melting AM of pure tungsten and molybdenum. We demonstrate that defect-free material can be obtained in both systems with appropriate processing. Strong build direction crystallographic texture fibers are observed in both systems. In molybdenum the fiber texture has direct impact on the resulting tensile behavior. These results demonstrate that electron beam AM is a suitable technology for processing these difficult to fabricate materials.