PREPARATION AND CHARACTERIZATION OF A TUNGSTEN COATING LAYER ON CuCrZr ALLOY FOR THE PLASMA FACING COMPONENTS OF THE EAST

摘要

In fusion devices, Plasma Facing Components (PFCs) suffer from damage from high thermal loads and bombardment of the plasma facing component, especially in the region near the divertor. For EAST, most of the surface in the upper divertor was covered with tungsten (W) Monoblock PFCs, by which high heat fluxes could be sustained, while PFCs of W plate fixed on a CuCrZr block have been used in some parts such as the divertor dome and baffles for lower heat loads due to their flexibility. However, sometimes, the CuCrZr block was eroded by intense plasma events like ELMs, VDE, and arcing, leading to the production of massive impurities. In this work, we proposed an approach to solve this problem by coating a W film on the CuCrZr block using the cathodic arc deposition method. The thermal behavior and suitability of the W film as a plasma facing component (PFC) was evaluated by using a DUT-PSI device. The four coatings of different thicknesses were tested under the same parameters. After a thermal test, the coating surface was analyzed by using the scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) technique. The results obtained provided the evidence that the W coating of thickness from 5 μm to 13 μm is capable of resisting a heat flux of up to 1 MW/m~2. The coating of thickness 17 μm showed some cracks as a result of the heat flux testing. The formation of cracks was started after the appearance of blisters on the coating surface which weakened the coating and initiated the formation of cracks. The blisters were removed to uncover the erosion. In our study, we found that W coating could be employed to protect the CuCrZr blocks of both the dome and baffle in the upper divertor in the EAST from aggressive heat environment.