Alloying and coating strategies for improved Pb-Li compatibility in DEMO-type fusion reactors

Two strategies were explored to improve the Pb-16Li compatibility of Fe-base alloys for a fusion energy blanket system. The use of thin (∼50 μm) Al-rich diffusion coatings on Grade 92 (9Cr-2W) substrates significantly reduced the mass loss in static Pb-Li capsule tests for up to 5000 h at 600 °C and 700 °C. However, significant Al loss was observed at 700 °C. Thicker coatings with Fe-Al intermetallic layers partially spalled after exposure at 700 °C, suggesting that coating strategies are limited to lower temperatures. To identify compositions for further alloy development, model FeCrAlY alloys with 10-20 wt.%Cr and 3-5%Al were exposed for 1000 h at 700 °C. There was little effect on mass change of varying the Cr content, however, alloys with <5% Al showed mass losses in these experiments. For both coatings and FeCrAl alloys, the surface reaction product was LiAlO₂ after exposure and cleaning.