Characterisation of Oxides by Advanced Techniques

Duchoň, Jan; Halodová, Patricie; Lorincink, Jan; Gabriele, Fosca Di; Hojná, Anna

doi:10.12776/ams.v24i1.1031

Cited by 6 publications

(7 citation statements)

References 18 publications

(28 reference statements)

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“…They were further analyzed by EDS and were identified as an outer Fe 3 O 4 and inner spinel-type Fe-Cr-O oxides. This is also in agreement with previous studies [19,20,21], where these oxides were defined as highly protective. For all the bend specimens observed, no trend of breaking through the oxide layer within the range of applied static stresses was established.…”

Section: Discussionsupporting

confidence: 93%

Effect of Applied Stress on T91 Steel Performance in Liquid Lead at 400 °C

et al. 2018

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The environmental performance of structural materials (e.g., corrosion and environmental assisted cracking) is one of the critical issues being addressed in the development of Generation IV fast reactors. This work aims to support the study of the performance of the ferritic-martensitic steel T91 in liquid lead, under close to operation conditions, in order to assess its suitability for an application in lead fast reactors. T91 steel was tested in air and liquid lead at 400 °C using static and slow loading regimes. Applied stresses were chosen to be slightly above the yield strength in order to evaluate the threshold stress and strain for crack initiation. Three-point bending static exposure and constant extension tests of tapered specimens were performed. Post-test surfaces and cross sections of specimens were observed using scanning electron microscopy techniques in order to detect cracks and to analyze oxide layers. The effect of strain rate of the oxide layer cracking was observed. In conclusion, T91 was not susceptible to liquid metal embrittlement, a special case of environmentally assisted cracking under the testing conditions. The cracking conditions are discussed based on previous experience.

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Section: Discussionsupporting

confidence: 93%

Effect of Applied Stress on T91 Steel Performance in Liquid Lead at 400 °C

et al. 2018

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“…Under the protective Pt layer, a complex oxide layer having thickness less than 1 μm can be observed. The oxide layer is formed by an inner spinel FeCr 2 O 4 and outer magnetite Fe 2 O 3 structure [17]. The crack tip was reached at a depth of ~46 µm beneath the specimen surface and from the BSE image of the cross-section it is evident that the crack tip is filled with material having high atomic mass (Figure 3).…”

Section: Resultsmentioning

confidence: 99%

Microstructural Investigation of LME Crack Initiated in Ferritic/Martensitic Steel T91 Loaded in Liquid Lead-Bismuth Eutectic at 300 °C

2018

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Liquid lead-bismuth eutectic (LBE) is one of the candidate materials for advanced nuclear systems. The structural materials used in contact with LBE are selected according to the resistance to liquid metal corrosion, irradiation embrittlement, and compatibility with the coolant. However, simultaneous presence of mechanical strain and LBE environment can induce liquid metal embrittlement (LME) in these materials. In this study, a specimen from candidate ferritic-martensitic steel T91 was tested by Constant Extension Rate Tensile (CERT) test exposed to PbBi environment with oxygen concentration 6 × 10−6 wt % at 300 °C up to rupture. Post-test examination using scanning electron microscopy (SEM) showed a deep crack indicating features of LME in the plastic strained region of the tested specimen. Further investigations focused on characterization of the fracture path and microstructure determination using focused ion beam (FIB) and energy dispersive X-ray spectrometry/electron backscatter diffraction (EDX/EBSD). This observation revealed that the dominant LME failure mode of the observed crack is translath or transgranular and the crack stopped at the high-angle grain boundary. The role of oxides in the crack initiation is discussed.

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“…The paper summarizes the key results of the new type of experiments for the T91 steel exposed in two lowflow HLM environments (Pb, PbBi-LBE) as well as the data, which were partially published in previous papers (Duchoň et al, 2018;Hojná et al, 2018a,b,c;Halodová et al, 2019). The conditions for occurrence (initiation) of the LME/EAC in the T91 in contact with the HLM are explained and discussed in the paper.…”

Section: Introductionmentioning

confidence: 85%

“…Detailed transmission electron microscopy (TEM) observation was performed on an FIB lamella cut from the specimen exposed for 2000 h in LBE (Duchoň et al, 2018). The outer oxide layer was identified by SAED (selectedarea electron diffraction) as magnetite, and the inner layer was identified as the Fe-Cr spinel.…”

Section: Static Exposure Testsmentioning

confidence: 99%

“…To verify the sensitivity of the T91 to the LME/EAC in simulated HLM operational conditions with application of the allowable stresses and oxygen-controlled chemistry, a new type of experiments was performed recently. The testing was focused on studying the LME/EAC crack initiation conditions in static HLM (Duchoň et al, 2018;Hojná et al, 2018a,b,c;Halodová et al, 2019). The sensitivity tests in the dynamic HLM are still to be performed.…”

Section: Introductionmentioning

confidence: 99%

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Environmentally assisted cracking of T91 ferritic-martensitic steel in heavy liquid metals

et al. 2020

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In order to advance material development for future nuclear systems, an insight into the cracking conditions of T91 ferritic-martensitic steel in heavy liquid metals (HLM) is provided. The paper critically reviews previous experimental data and summarizes them with new results. The new testing of T91 steel was performed in contact with slow flow and static HLM to study crack initiation, especially in liquid PbBi eutectic at 300°–350°C and Pb at 400°C with about 1 × 10−6 wt.% of oxygen. Pre-stressed coupons were exposed to the liquid metals for up to 2000 h. Constant extension rate tests (CERTs) were performed in the liquid metals to accelerate cracking development. Under static conditions, the testing resulted in oxidation without any crack observation. Under the CERT ones, the T91 steel showed a tendency to crack initiation in PbBi, while in Pb, cracks were not initiated even when the oxide layer was broken. Moreover, the environmentally assisted crack initiated at the maximum load and continued to grow under further loading without unstable failure. Both previous and new data have confirmed that high stress and plastic strain are pre-conditions for the environmentally assisted cracking of T91 in static HLM. It indicates that in the systems utilizing continuous oxygen control of HLM, the LME/EAC of the T91 could develop only in the beyond design load conditions. Further testing is necessary to address the HLM flow speed effect.

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Characterisation of Oxides by Advanced Techniques

Cited by 6 publications

References 18 publications

Effect of Applied Stress on T91 Steel Performance in Liquid Lead at 400 °C

Effect of Applied Stress on T91 Steel Performance in Liquid Lead at 400 °C

Microstructural Investigation of LME Crack Initiated in Ferritic/Martensitic Steel T91 Loaded in Liquid Lead-Bismuth Eutectic at 300 °C

Environmentally assisted cracking of T91 ferritic-martensitic steel in heavy liquid metals

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