Net shaping of tungsten components by micro powder injection moulding

Abstract

For future fusion power plants, a He-cooled divertor design has been developed by the Forschungszentrum Karlsruhe. The divertor, as one of the plasma facing components has to withstand high heat loads of 10 MW/m 2 as well as sputtering due to ion impact on the surface of the divertor. Tungsten is considered to be the most promising material to be used for this application. Because of the high hardness of tungsten, fabrication of these parts by standard shaping technologies for steels such as milling is depending on the design, either difficult or even impossible. Thus, powder injection moulding (PIM) as a way for time and cost effective net shape fabrication of ceramics and metals, has been developed for tungsten. The key steps in injection moulding such as feedstock formulation, the injection moulding process itself as well as debinding and sintering were studied. A tungsten feedstock with an optimised solid load of 55 vol.% was developed and successfully tested in injection moulding experiments applying complex shaped cavities. Thermal consolidation of injection moulded components lead to a sintered density of approximately 96% and a grain size of approximately 18 μm. For final densification and grain size reduction, hot isostatic pressing (HIP) was investigated.