A comparison of two high spatial resolution imaging techniques for determining carbide precipitate type and size in ferritic 9Cr-1Mo steel

Liu, Chong; Heard, Peter J; Payton, Oliver D; Picco, Loren; Flewitt, Peter

doi:10.1016/j.ultramic.2019.06.005

Cited by 9 publications

(10 citation statements)

References 20 publications

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“…After a few seconds of rapid beam scanning at 150 pA/30 kV to allow for excess-gas to be sputtered away, imaging was resumed. As per previous work [39] the XeF 2 adhered to the oxide-free metal surface and not the carbide precipitates. Whilst a full description of the process is beyond the scope of this paper, the XeF 2 gas increases the secondary electron yield of the metal surface and improves contrast to highlight the carbides [39] .…”

Section: Characterisation Techniquessupporting

confidence: 80%

“…As per previous work [39] the XeF 2 adhered to the oxide-free metal surface and not the carbide precipitates. Whilst a full description of the process is beyond the scope of this paper, the XeF 2 gas increases the secondary electron yield of the metal surface and improves contrast to highlight the carbides [39] . Counting statistics were obtained using a series of simple image processing tools, including a custom LabView script for area % counting.…”

Section: Characterisation Techniquessupporting

confidence: 80%

“…4. b) reveals the homogeneous distribution of ~400 nm diameter carbide precipitates preferentially at prior austenite grain boundaries [39] . An EBSD scan ( Fig 4 .…”

Section: Microstructure Of As-received Eurofer-97mentioning

confidence: 99%

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The effects of fusion reactor thermal transients on the microstructure of Eurofer-97 steel

Kumar

Hargreaves

Bharj

et al. 2021

Journal of Nuclear Materials

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Plasma-wall interactions in a commercial-scale fusion power station may exert high transient thermal loads on plasma-facing surfaces, repeatedly subjecting underlying structural materials to high temperatures for short durations. Specimens of the reduced activation ferritic-martensitic steel Eurofer-97 were continuously aged at constant temperature in the range of 550 °C to 950 °C for up to 168 hours in a furnace to investigate the microstructural effects of short-term high temperature exposure. A CO 2 laser was also used to repeatedly heat another specimen from 400 °C to 850 °C a total of 1,480 times over a period of 41 hours to explore transient heating effects. Microstructural changes were studied via scanning electron and focused ion beam microscopy and include (i) the coarsening of Cr-rich secondary phase precipitates when continuously heated above 750 °C, (ii) an increase in average grain size above 800 °C and (iii) the evolution of a new lath martensite microstructure above 850 °C. Conversely, transient heating via a laser was found to result in the decomposition of the as-received lath martensite structure into ferrite and Cr-rich carbide precipitates, accompanied by a significant increase in average grain size from 0.1-2 μm to 5-40 μm. Experimental analysis was supported by thermodynamic simulation of the equilibrium phase behaviour of Eurofer-97 in MatCalc and thermal finite element modelling of plasma-wall interaction heating on the water-cooled lithium-lead tritium breeding blanket concept in Comsol Multiphysics. Simulated thermal transients were found to significantly alter the microstructure of Eurofer-97 and the implications of this are discussed.

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Section: Characterisation Techniquessupporting

confidence: 80%

Section: Characterisation Techniquessupporting

confidence: 80%

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The effects of fusion reactor thermal transients on the microstructure of Eurofer-97 steel

Kumar

Hargreaves

Bharj

et al. 2021

Journal of Nuclear Materials

Self Cite

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“…XeF2 gas was then introduced into the chamber for a few seconds to functionalise the surface and accentuate the contrast of the carbide precipitates. With the introduction of XeF2, the resulting images have reduced ion channelling contrast but show carbide precipitates as darker regions [16].…”

Section: Materials and Experimentsmentioning

confidence: 99%

“…Changes in the mechanical and corrosion properties occur as a result of thermal ageing, oxidation and carburisation in the coolant gas containing CO2 with traces of CO, H2, H2O and CH4. The consideration of service life extension of AGRs has revived the interest in 9Cr-1Mo steel and prompted the study of the mechanisms of concurrent oxidation and carburisation [6] [7] [8]. The thermodynamic equilibrium reaction governing carburisation is shown by equation 1 [6] [9]:…”

Section: Introductionmentioning

confidence: 99%

Carbide precipitation associated with carburisation of 9Cr–1Mo steel in hot CO2 gas

et al. 2019

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Experimental ferritic 9Cr-1Mo steels exposed at high temperature and pressure to CO2-based gas undergo oxidation and carburisation. Oxidation proceeds initially as a protective phase with parabolic kinetics (stage I). At high temperatures and longer times, more rapid "breakaway" oxidation occurs (stage II). Post-breakaway oxidation follows linear kinetics (stage III). A virgin sample and three oxidised samples were selected for analysis. Precipitates embedded in the matrix with four different morphologies were observed using focused ion beam imaging, X-ray diffraction and electron microscopy techniques. Coarse carbides (M23C6) were observed as the predominant precipitates in all four samples. Fine needles (M2C), large needles (MC) and cored coarse carbide precipitates (M23C6) were also present in stages (I), (II) and (III), respectively. TEM analysis was used to give the lattice types and orientations of the carbides found. Energy-dispersive X-ray analysis was used to obtain compositions. The precipitation is considered particularly with respect to the formation of cored M23C6 carbide precipitates. These data provide a threshold for the matrix composition that defines the onset of breakaway oxidation.

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Insights into primary carbides and nanoparticles in an additively manufactured high-alloy steel

Zhang,

Peng,

Bagot

et al. 2024

Acta Materialia

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A comparison of two high spatial resolution imaging techniques for determining carbide precipitate type and size in ferritic 9Cr-1Mo steel

Abstract: A comparison of two high spatial resolution imaging techniques for determining carbide precipitate type and size in ferritic 9Cr-1Mo steel.

Cited by 9 publications

References 20 publications

The effects of fusion reactor thermal transients on the microstructure of Eurofer-97 steel

The effects of fusion reactor thermal transients on the microstructure of Eurofer-97 steel

Carbide precipitation associated with carburisation of 9Cr–1Mo steel in hot CO2 gas

Insights into primary carbides and nanoparticles in an additively manufactured high-alloy steel

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