Development of tungsten coatings for ITER divertor components

The EU design of the ITER Divertor Wing envisages the use of tungsten as an armour because of its low sputter rate. To guarantee an adequate armour lifetime a minimum thickness of 5 mm is required. A promising technology to apply W as an armour for extended surfaces is the plasma spray process (PS). Aim of the activity was qualifying a PS able to realise up to 5 mm thick W coating on Copper Chromium Zirconium (CuCrZr) tube substrate (Dout=50 mm, Din=40 mm and length=150 mm) to be tested with respect to thermal fatigue under high heat flux. Several samples were manufactured, and in particular: many flat samples for selection of the spraying parameters; four tubular samples 50 mm long with W coating thickness of 4 mm; two tubular mock ups 150 mm long with coating thickness of 3 and 5 mm. Thermal fatigue tests were performed at the electron beam facility FE200 (Le Creusot-France). The mock up with 5 mm thick W coating realised with the low pressure plasma spray technique survived without any damage 1000 cycles at 2 MW/m/sup 2/ and 200 cycles at 4 MW/m/sup 2/.