Effects of surface roughness, shot peening, and plasma-assisted elemental surface modification on corrosion resistance of steels for use in lead-alloy cooled fast reactors

The selection and development of structural materials with long-term stability against corrosion in a lead-alloy environment is an important research area for the Generation-IV Lead-alloy Cooled Fast Reactors (LFR). The effects of surface roughness, plasma-assisted elemental surface modification, and shot-peening on corrosion performance of advanced ferritic-martensitic steels exposed to liquid lead-bismuth eutectic are reported. Surface roughness is found to have a distinct effect on intergranular corrosion and correlates with oxide thickness. Shot peening is found to inhibit intergranular corrosion up to the point where the metal is no longer affected by the treatment. Directly implanting oxygen ions into the surface can provide some control over oxide growth forming a stable thin oxide prior to exposure. Plasma-immersion-ion-implantation and deposition of Si, Ta, and to a lesser extent Y is found to be an effective technique for mitigating bulk oxidation and liquid metal attack when appropriately applied. (authors)