1: Associazione EURATOM-ENEA sulla Fusione, PB 65 - I-00044 Frascati (Rome), Italy
2: Centro Sviluppo Materiali, via di Castel Romano 100, 00129 Rome, Italy
3: Framatome, 71200 Le Creusot, France
4: The NET Team c/o Max Plank-Institute fuer Plasmaphysic, Boltzmannstr. 2, D-85748 Garching, FRG

The EU design of the ITER Divertor Wing envisages the use of tungsten as armour because of the W low sputter rate. To guarantee an adeguate armour lifetime a minimum thickness of 5 mm is required. A promising technology to apply W as armour of extended surfaces is the Plasma Spray Process (PS). The aim of the activity has been to qualify a PS able to realise up to 5 mm thick W coatings on Copper Chromium Zirconium (CuCrZr) tubes (D_out=50 mm, D_in=40 mm and length=150 mm) to be tested with respect thermal fatigue under High Heat Flux (up to 5 MW/m²).

The key issues of the activities are related to:
- the efficiency of the deposition that affect the possibility to get relevant thickness of the coatings;
- the control of the substrate temperature during the deposition in order to prevent the detachment of the coating at the end of the process;
- the optimisation of the spraying parameters in order to get the highest adhesion of the coating to the substrate and the best properties of the sprayed W;
- the selection of the most suitable bond coat layer to guarantee good adhesion and compliance between W and Copper alloy.

During the manufacturing campaign two technologies have been utilised in order to realise the mock ups : Low and High Pressure Plasma Spray. The selection of the bonding interlayer was crucial in order to get good adhesion of the coating to the CuCrZr substrate.

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 have been performed at the electron beam facility FE200 (CEA-Framatome-Francia).
The mock up with 5 mm thick W coating realised with Low Pressure Plasma Spray technique survived without any damage to 1000 cycles at 2 MW/m² and 200 cycles at 4 MW/m²: it is the first time that 5 mm thick coating on Cu alloy substrate survives to the above thermal cycles. In the next future, the test campaign will be completed on the same mock up performing cyclic tests up to the maximum performance achievable.

The R & D activities will continue by:
- optimising the processes in order to improve the coating performances and manufacturing other mock ups to increase the thermal fatigue experimental data base;
- qualifying the coatings with respect physical and mechanical properties.