Due to the relatively high strayfield radiation (140 GHz) from the electron cyclotron radio frequency heating system to which the W7-X cryopumps are expected to be subjected, coating systems acting as an efficient absorber for 140 GHz radiation have been developed for the water-cooled baffle shield in order to reduce the thermal load on the liquid N shield and the liquid He cryopanel.Several types of oxide ceramic coatings were applied on planar copper substrates by Atmospheric Plasma Spraying. The influence of the process parameters on the coating properties and microwave absorbing capability was analyzed. It was found that film thickness and microstructure of the sprayed coatings have a significant influence on microwave absorption behaviour. For Al 2 O 3 /TiO 2 coatings, absorption values over 90% were obtained for the 140 GHz probing beam.After optimization of the coating structure for maximum microwave absorption, the coating procedure was adapted by special robot trajectories to the complex water baffle geometry. The selected spray parameters and kinematics were then used for the complete coating of four mock-ups, which have been tested in the W7-X strayfield test facility Mistral. The mock-ups showed absorption values of 75%.

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Coating operations over glass ceramic substrates represent a new field for thermal spray applications. Due to the unique thermal and mechanical properties of glass ceramics, especially the low or even negative CTE, coating processes must be adapted to reduce the distribution of thermal stresses in the system and to not damage the substrate. This study investigates the deposition of a complex-shaped ceramic-metallic multilayer coating system that could potentially serve as a heating element in a glass ceramic cooking plate. To ensure coating adhesion, the substrates are preheated and their surfaces are grit blasted. In order to minimize stresses associated with the deposition of metal, the movement of the spraying mechanism was automated with robot control and new masking concepts were developed to ensure the accuracy of the shape and placement of the coating. The influence of spraying parameters on coating properties and residual stress distribution is analyzed as well.