Abstract
Thermonuclear fusion is a promising source of clean energy for the future. Max-Planck-Institute für Plasmaphysik (IPP, Greifswald, Germany) is currently working on the new type of fusion reactor, the stellarator Wendelstein 7-X. The extreme operating conditions of fusion reactor devices have lead to an increasing interest in the field of high performance materials. The present work describes the development of coating systems acting as efficient absorbers for 140 GHz radiation, which is the microwave frequency to which the analyzed components of Wendelstein 7-X are subjected. Several types of oxide ceramic coatings were applied by Atmospheric Plasma Spraying. Different powders were used as feedstock material for the coating operation. The influence of the process parameters on the coating properties and microwave absorbing capability was analyzed. The coatings microstructure and mechanical properties were characterized in terms of porosity, microhardness, roughness, adhesion and residual stresses. XRD and SEM were carried out. It was found that thickness and microstructure of the coatings have a significant influence on microwave absorption behavior. For Al2O3/TiO2 coatings, absorption values over 90% were obtained. After optimization of the coating structure, the coating process was adapted to several real reactor components that will work in Wendelstein 7-X.
