Erosion-corrosion of RAFM JLF-1 steel in Lithium flow induced by impeller
The purpose of the present study is to investigate erosion-corrosion characteristics of reduced activation ferritic martensitic steel, JLF-1 (Fe-9Cr-2W) in flowing Li. The erosion-corrosion characteristics were investigated by means of corrosion tests with rectangular plate type specimen of JLF-1 in Li stirring pot, where the Li flow was induced by impeller in the pot. The test temperature was 500 C and 600 C, and there was no temperature difference in the Li stirring pot. The erosion-corrosion characteristics were evaluated by the weight loss measurement of the specimens and metallurgical analysis for the corroded surface. The results were compared with those obtained from the tests at static condition to feature the effect of Li flow on the corrosion. The weight loss of the specimens tested in Li flow was larger than that tested in the static tests. The corroded surface showed the local corrosion along lath boundary and grain boundary of JLF-1 as the same as that after the test at static condition. There were defects which were not observed in the specimen tested at the static condition. The defects were the trace of the erosion-corrosion. The corrosion attack to the boundaries made weak bonding between the subgrains, and the subgrains were peeled from the surface by the Li flow.
Effect of nitrogen on the corrosion behavior of RAFM JLF-1 steel in lithium
Abstract The corrosion behavior of RAFM JLF-1 (Fe–9Cr–2W) steel in static N-added Li (0.5 wt.%N) at 600 °C for times up to 750 h was investigated. The kinetics of weight change and peculiarities of corrosion interaction were determined. Samples showed intensive weight losses during first 120 h while with an exposure time the weight losses became slower. Corrosion attack proceeded most intensively along the boundaries of prior austenitic grains, martensite packets and laths, causing formation of the extremely relief surface. The porous and softened ferrite zone depleted markedly in Cr was formed beneath the relief surface. The martensite to ferrite transformation occurred in this zone. The weight losses of steel in N-added Li were about 25 times higher than those in “pure” Li (0.004 wt.%N) under the same time–temperature conditions of tests. The scheme of corrosion interaction in “JLF-1 steel–Li[N]” system was proposed.
The interaction of chromium with nitrogen dissolved in liquid lithium
Abstract The ternary nitride, Li9CrN5, has been identified as the product of the reaction of paniculate chromium with nitrogen dissolved in liquid lithium, using X-ray powder diffraction (solid-state chemistry) and electrical resistivity (solution chemistry) methods; the minimum nitride activity required for the formation of this material is less than 0.0025 at 475°C. The reaction kinetics are first order with respect to dissolved nitride. Austenitic stainless steel (A1S1 316) also removes dissolved nitride from liquid lithium at 475°C with the formation of Li9CrN5 as the surface product. X-ray powder diffraction studies of the solid-state reactions between various molar ratios of lithium nitride and either chromium or chromium (III) oxide have been undertaken. Whereas reaction with chromium invariably yields Li9CrN5, reaction with chromium (III) oxide gives Li2O, CrN, Li9CrN5 and the solid-solution phase, Li 9 CrN 5 · 9 2 Li 2 O , in varying ratios. Differential thermal analysis of the lithium nitride-chromium reaction showed a large exothermic reaction at 706°C. The ternary nitride, Li9CrN5, and the solid-solution phase, Li 9 CrN 5 · 9 2 Li 2 O both crystallise with face-centered cubic anti-fluorite lattices with cell dimensions of 14.22 A and 4.72 A, respectively.