Study on the effect of Si content on the compatibility of F/M steels with lead-bismuth eutectic using small punch testing

Abstract

This study investigates the impact of silicon (Si) on the corrosion resistance and post-corrosion toughness of ferrite/martensitic (F/M) steels in a liquid lead-bismuth eutectic (LBE) environment. Corrosion tests were performed on HT-9 and EP-823 (1.17 wt% Si) steels at 550 °C for 1000 h under oxygen-controlled conditions. The resulting oxide layer consisted of an outer magnetite layer, a spinel layer and an inner oxide zone (IOZ). A Si-rich oxide layer was identified within the spinel and IOZ layers of EP-823, which slowed the growth rate of the oxide layer, enhanced antioxidant performance, and inhibited dissolution corrosion by the LBE. Post-corrosion mechanical properties were evaluated using a small punch test. Results showed a significant reduction in HT-9's toughness within 240 h of corrosion, while EP-823 exhibited increased brittleness after 500 h due to Si-promoted carbide and Laves phase precipitation, significantly reducing its toughness.