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In the course of developing functionally graded tungsten/steel-layer systems as protective coatings for the first wall (FW) of future fusion reactors, an overview of the results attained so far is given. This includes the determined parameters for creating such systems by vacuum plasma spraying on a laboratory scale and the achieved material properties determined in previous works. To realize the coating of future full scale FWs as well, the coating process is adapted to larger coating areas in the form of mock-ups. For such components, special attention needs to be paid to the challenges of the limited temperature window during coating to achieve good coating adhesion, whilst avoiding exceeding the tempering temperature of the steel. One successfully coated mock-up is also exposed to fusion-relevant heat loads in HELOKA (Helium Loop Karlsruhe) to evaluate the coating system behavior and verify its durability. Finally, for even larger components the coating design and process are further optimized, supported by finite element simulations.

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Cylindrical samples of iron, austenitic steel 1.4571, and nickel‐based alloy 2.4663 were tested in liquid tin (Sn) at 500 and 700 °C. The exposure times ranged from 3 to 100 h. During exposure the oxygen content of the melt was measured online. In case the oxygen content is higher than the oxide threshold, even Fe‐oxides, which were not specifically created before exposure, are capable of reducing liquid Sn corrosion. In case of lower oxygen contents more stable oxides, like Cr‐oxides, fail locally leading to corrosion pits. The influence of saturation with the parent element of the tested alloy on material consumption and morphology of corrosion scales was also investigated. Saturation reduces material consumption and promotes formation of intermetallic compounds of the respective parent element and Sn. The capacity of liquid Sn for taking up nickel leads predominantly to selective removal of nickel from the corrosion scale on austenitic steel and nickel‐based alloy samples, whereas the less soluble elements remain. Finally, typical rate laws were tested for expressing the observed material consumption as a function of time.