Liquid metal embrittlement of silicon enriched steel for nuclear applications

Lead–bismuth eutectic (LBE) liquid metal is considered to act as the coolant and as spallation neutron source for a future accelerator driven system (ADS). In addition to the highly corrosive effect of the liquid lead–bismuth eutectic, the liquid metal may also affect the mechanical integrity of the structural materials by a phenomenon called liquid metal embrittlement. Thus, although the addition of silicon to ferritic–martensitic steels has been found to strongly increase the material’s resistance to corrosion in liquid lead–bismuth environment, their mechanical properties can be strongly affected by the liquid metal environment. This paper discusses the mechanical properties of an experimental silicon enriched high Cr/high creep resistant bainitic steel when in contact with LBE. The steel’s mechanical properties were assessed by tensile testing as function of temperature in both liquid lead–bismuth eutectic and in an argon and hydrogen gas environment. It was found that the silicon enriched bainitic steel is very prone to liquid metal embrittlement between 300 and 375 °C with the transition in mechanical behaviour from ductile to predominantly brittle between 200 and 300 °C thus defining its the so-called ductility trough.