Corrosion characteristics of low activation ferritic steel, JLF-1, in liquid lithium in static and thermal convection conditions

The compatibility of JLF-1(Fe–9Cr–2W–0.1C), a reduced activation ferritec/martensitic (RAFM) steel with static and flowing lithium (Li) was investigated. The corrosion characteristics were studied by means of measurement of weight losses and scanning electron microscope (SEM)/energy dispersive X-ray spectrometer (EDS) analysis on the surfaces and cross-sections of the specimens. The weight losses of JLF-1 specimens showed saturation at the temperature of 500 °C and 600 °C. This is possibly due to the saturation of Fe, Cr in bulk Li or formation of saturated layer of dissolved elements in liquid Li near the specimen surface. In the corrosion test in a thermal convection loop, the corrosion rate at 500 °C for 250 h was significantly larger than that obtained in the static test in an identical condition. After Li exposure, the phase transformation from martensite to ferrite was found on the specimens. The chemical analysis results and the loss of carbides suggested that the phase change was caused by the depletion of carbon. At the same time, selective depletion of alloy elements, such as Cr and W was detected by EDS on the surface. The result of Vickers hardness test showed that obvious softening occurred on the surface of the specimens after Li exposure and the depth of the softened region was consistent with that of the phase transformation. The flowing Li enhanced the weight loss, phase change and hardness reduction due to the mass transfer.