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.
The Investigation of Corrosion Behaviors of Type 316L Stainless Steel in Stagnating Liquid Lithium
Abstract The corrosion behavior of Type 316L stainless steel in stagnating liquid Li under an elevated-temperature environment was investigated using a scanning electron microscope and an energy dispersive X-ray detector and self-designed laser-induced breakdown spectroscopy. A nonuniform and cell-like branched structure separated by distinct boundaries was observed, and a porous and rugged corroded layer was formed on the surface of the substrate after 500 h exposing 350°C liquid Li. This showed that the intensity of the Cr element on the superficial corroded sample decreased significantly when the depth reached ~2.8 μm and then was gradually restored in the range of ~5.6 μm. Meanwhile, the intensity of the Li element revealed consistent reduction to zero at ~4.0 μm. This study disclosed element transfer and penetration along a depth in the corrosion process between the liquid lithium and steel matrix.
Traceability strategy for gear-pitch-measuring instruments: development and calibration of a multiball artifact
There is a strong demand to ensure the traceability of gear-measuring instruments (GMIs). We propose a multiball artifact (MBA) for the evaluation of pitch-measuring accuracy. The aim of the MBA is to transfer the minimum uncertainty from a calibrated value at the National Metrology Institute of Japan (NMIJ) to a measured value of GMIs at a shop floor. The MBA is composed of equally spaced high-accuracy balls around an axis. The pitch-measuring accuracy of GMIs is evaluated by measuring the angular pitch deviation of the balls instead of the angular pitch deviation of a gear. We calibrated the angular pitch deviation using a coordinate measuring instrument (CMM) at the NMIJ and adapting a multiple-orientation technique. We proposed a calibration strategy of the angular pitch deviation. The calibration value of the pitch deviation for the MBA at the NMIJ was obtained with a measurement uncertainty (U95) of 0.2 µm. We evaluated the pitch-measuring accuracy of a GMI using the calibrated MBA. Each value of U95 for the cumulative and single pitch deviations for the left and right flanks was less than or equal to 0.5 µm. The small uncertainty was transferred from the NMIJ to the GMI.