Mikel Garitano^1,2, Rocío Ortiz¹, Oihane Hernández-Rodríguez¹, Lucia Mendizabal¹, Eva G. Berasategui^1
1TEKNIKER, Eibar, Spain
²University of the Basque Country (UPV/EHU), Bilbao, Spain
Tungsten is widely considered for magnetic fusion reactors due to its high melting point and low sputtering yield. However, its high hydrogenic diffusivity limits its effectiveness as a tritium permeation barrier. In this work, W/SiC multilayer coatings were developed to combine the plasma-facing performance of tungsten with the low hydrogenic diffusivity of silicon carbide. In addition, SiC offers higher irradiation resistance and chemical compatibility with lithium, which is used in breeding blankets for in-situ tritium generation. Initially, tungsten coatings approximately 1.5 µm thick were synthesized by magnetron sputtering to perform a systematic comparison between DC, pulsed-DC and High-Power Impulse Magnetron Sputtering (HiPIMS) deposition modes. HiPIMS-deposited coatings showed increased hardness, enhanced densification and lower surface roughness. Subsequently, silicon carbide coatings around 1 µm thick were developed by means of pulsed-DC sputtering. Deposition parameters were adjusted and optimized so as to obtain amorphous microstructures and hardness values comparable to those of the tungsten coatings, thereby promoting mechanical compatibility within the multilayer structure. This sequential process optimization enabled the synthesis of the W/SiC multilayer coatings with a total thickness of 1.5 µm. Multilayer architectures with an increased number of interfaces exhibited improved adhesion, as revealed by mechanical testing, likely due to more effective defect staggering. Current efforts focus on engineering smoother W/SiC transitions and multilayer architecture to reduce hydrogen transport and enhance the overall coating performance under demanding fusion-relevant conditions.