Structuring of tungsten by pulsed ECM processes for He-cooled divertor application

A He-cooled divertor is based on components fabricated from tungsten alloys. Standard shaping processes, e.g., turning or EDM cutting are often too expensive and are able to introduce structural defects into the work pieces. Electro-Chemical Machining (ECM) as a new fabrication method is known to be cost efficient and gentle to materials surfaces. However, ECM was originally not developed for working of tungsten due to difficulties existing in standard processes, mainly coming from the specific electrochemical properties of tungsten. Performed electrochemical investigations showed that tungsten can be dissolved similar to steels by applying a newly adopted electrolyte which overcomes passivation. These results opened the paths to examine different ECM variants (M-ECM, C-ECM) for electrochemical structuring processes of tungsten. For C-ECM, structuring was analyzed depending on physical parameters like electrode distance and type of DC current. Especially for pulsed C-ECM, the dependency of structure accuracy and erosion rate are discussed in this matter.