Development of a process for tungsten components

For future fusion power plants, a high amount of tungsten components will have to be fabricated for the plasma facing components. Due to the materials properties of tungsten (high melting point, high hardness, high sputtering resistance, high thermal conductivity) a cost-effective production of components is needed. Powder Injection moulding (PIM) as a method to prepare complex shaped parts in large-scale serious production at a comparably low price might be a suitable way to solve this task. Thus, a complete PIM production process including feedstock formulation, injection moulding, debinding and thermal consolidation was developed for tungsten components. To improve the PIM performance various W powders with a particle size between 0.7 μm FSSS and 3.0 μm FSSS were tested regarding feedstock viscosity and sintering activity. This investigation was performed before and after powder deagglomeration by jet milling. Deagglomeration was found to be necessary for low feedstock viscosity at a powder loading larger 50 Vol.% as well as for enhanced sinter ability. For a low feedstock viscosity, a powder particle size larger 2.0 μm FSSS was found to be superior, while the sintering activity increases with decreasing particle size. Thus further experiments were done, applying a powder with a particle size slightly below (1.2 μm FSSS) and above (2.5 μm FSSS) the superior particle size of 2.0 μm FSSS. By powder injection moulding laboratory samples like e.g. cooling promoter for a Helium cooled divertor according the Slot Array design were replicated applying an optimized feedstock system. Density measurements of tungsten components after sintering at a temperature above 2000 C in H2 showed a density of 19.14 g/cm3 for a powder with a particle size of 1.2 μm FSSS and of 18.37 g/cm3 for 2.5 μm FSSS, respectively. Further on the hardness of these samples was tested and a hardness comparable to recrystallized tungsten was detected (1.2 μm FSSS: 357HV10; 2.5 μm FSSS: 324HV10; recrystallized after Lassner and Schubert: 300HV30). (orig.)