Advanced electro-chemical processing of tungsten components for He-cooled divertor application

Standard shaping processes for tungsten divertor components are expensive and introduce structural defects into the work-pieces. Although ECM (Electro-Chemical-Machining) as cost efficient and defect-free fabrication method is well known, it is not used in tungsten working, coming from the specific electro-chemical properties of W, incompatible with common ECM technique. Performed electro-chemical investigations showed the ways to overcome passivation by applying newly adapted electrolytes.These results opened the paths to develop and examine different ECM variants for electro-chemical structuring processes of tungsten. In general, those ECM application routes showed that electro-chemical treatment produces smooth surfaces without dangerous micro-cracks due to electro-polishing effects in atomic scale. The successful bulk shaping of W parts by ECM, e.g. used as heat promoters in the cooling fingers in divertor application, can also be applied to parts of macroscopic shape, e.g. thimbles or in castellation of tiles. This progress in ECM technology will surely positively affect the possibility to use/machine W as structural material in future.