Tungsten coatings repair: An approach to increase the lifetime of plasma facing components

The lifetime of tungsten coatings used for Plasma Facing Components (PFCs) in fusion devices is mainly limited by two degradation mechanisms occurring during the operation of the tokamak: erosion resulting from exposure to long plasma discharges (long term) and local damages caused by transient events (runaway electrons,..). An alternative solution to the current replacement of damaged PFCs would be to repair their surface by stripping the damaged tungsten coating and depositing a new one. In this paper, the process of removing tungsten was investigated on CuCrZr samples coated with a 15 mu m layer of W using four techniques: plasma etching, sandblasting, chemical attack and laser ablation. For each technique, etching properties were assessed by means of microscopic observations, topographical surface analyses and chemical analysis. The results presented here also highlight the issues related with controlling the etching depth and size of the treated surface.