Abstract
In this work, the conditions for the occurrence of Liquid Metal Embrittlement (LME) in the ferritic-martensitic steel T91 in contact with lead, Pb, were examined. Slow tensile tests with notched specimens revealed that in a temperature range close to the melting point of Pb, the steel is sensitive to LME (350–400 °C) and to Solid Metal Induced Embrittlement (SMIE) (300 °C). The cracking was stimulated by wetting (using a chemical flux) and the notch effect. It was found that the multi axial stresses state and the high level of plastic strain in front of the notch were the key factors triggering crack initiation.
Highlights
The interaction between structural materials and coolant is one of the most critical issues in the development of Lead cooled Fast Reactors (LFR)
In the temperature range between 350 and 550 ◦ C, which are relevant for LFR, the liquid metal embrittlement (LME) and the surface oxidation/dissolution are being studied among the most relevant degradation mechanisms
Because of the fact that stress-strain curves cannot be evaluated for notched specimens, and because of the lack of extensometers for the specimens tested in liquid Pb, load-displacement curves experimentally obtained were analyzed (Figure 3), in order to avoid inaccurate interpretation curves experimentally obtained were analyzed (Figure 3), in order to avoid inaccurate interpretation of the data
Summary
The interaction between structural materials and coolant is one of the most critical issues in the development of Lead cooled Fast Reactors (LFR). In the temperature range between 350 and 550 ◦ C, which are relevant for LFR, the liquid metal embrittlement (LME) and the surface oxidation/dissolution are being studied among the most relevant degradation mechanisms. LME is the tendency of structural materials to low energy fracture under stress in contact with liquid metals; the phenomenon is typically associated with a change from ductile to a cleavage-like fracture mode. LME is usually most severe just above the melting point of the liquid metal and it disappears with increasing temperature [1]. The embrittlement can occur even under the melting temperature of the liquid metal. The Solid Metal Induced Embrittlement (SMIE) is much less severe than the LME [2], even if it has the same microstructural features
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