Microstructural and Mechanical Property Evaluation of the Ferritic-Martensitic Steel under Liquid Sodium Environment

摘要

Studies were carried out to assess the microstructural and mechanical properties of ferritic-martensitic steel under a flowing sodium environment. HT9 (12Cr-MoVW) and Gr.92 (9Cr-MoVNbW) steel were exposed to liquid sodium at 650°C containing dissolved oxygen of 20 ppm for 2333 hours and evaluations of the microstructure as well as the mechanical properties of the microhardness and nanoindentation were carried out. The result showed that both HT9 and Gr.92 exhibited macroscopic weight loss caused by general corrosion as well as localized types such as intergranular corrosion and pitting. Decarburization at the steel surface took place as the test proceeded. As the Cr content increased, dissolution and decarburization were suppressed. Assessment of the actual cladding geometry revealed that an aging process rather than decarburization governed the mechanical properties, which resulted in a decrease of the microhardness and yield stress.