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An Fe–10Cr–4Al alloy containing reactive elements developed for application in high-temperature liquid lead environments was analyzed after exposure in 600 and 750°C lead with dissolved oxygen for 1,000–2,000 h. Atom probe tomography, transmission electron microscopy, and X-ray scattering were all used to study the protective oxide formed on the surface. Exposure at 750°C resulted in a 2-μm thick oxide, whereas the 600°C exposure resulted in a 100-nm thick oxide. Both oxides were layered, with an Fe–Al spinel on top, and an alumina layer toward the metal. In the 600°C exposed material, there was a Cr-rich oxide layer between the spinel and the alumina. Metallic lead particles were found in the inner and middle parts of the oxide, related to pores. The combination of the experimental techniques, focusing on atom probe tomography, and the interpretations that can be done, are discussed in detail.

In this paper, we investigated the possibility of applying the low power pulse laser welding technology to surface a protective layer against heavy liquid metal corrosion in fuel cladding tube made of austenitic 316L stainless steel. Based on results from flaring, flattening, bending tests and metallographic microscope investigations, we can preliminarily confirm the possibility of using low power pulse laser with specific power input to weld Fe-10Cr-4Al-RE alloy on the outer surface of a 316L stainless steel tube with the inner diameter of 11.8 mm and wall thickness of 0.65 mm.

Today the technical limit for solar towers is represented by the temperature that can be reached with current accumulation and exchange fluids (molten salts are generally adopted and the max temperatures are generally below 600 °C), even if other solutions have been suggested that reach 800 °C. An innovative solution based on liquid lead has been proposed in an ongoing experimental project named Nextower. The Nextower project aims to improve current technologies of the solar sector by transferring experience, originally consolidated in the field of nuclear plants, to accumulate heat at higher temperatures (T = 850–900 °C) through the use of liquid lead heat exchangers. The adoption of molten lead as a heat exchange fluid poses important criticalities of both corrosion and creep resistance, due to the temperatures and structural stresses reached during service. Liquid lead corrosion issues and solutions in addition to creep-resistant material selection are discussed. The experimental activities focused on technical solutions adopted to overcome these problems in terms of the selected materials and technologies. Corrosion laboratory tests have been designed in order to verify if structural 800H steel coated with 6 mm of FeCrAl alloy layers are able to resist the liquid lead attack up to 900 °C and for 1000 h or more. The metallographic results were obtained by mean of scanning electron microscopy with an energy dispersive microprobe confirm that the 800H steel shows no sign of corrosion after the completion of the tests.

A lean-alloyed FeCrAl steel have been developed by KTH and Kanthal and tested in liquid lead environments at 800°C and 900°c, as well as at 550°C with and without impurities and varying oxygen activates. The results demonstrate that the lean alloyed FeCrAl steel shows superior oxidation performance up 800°C. Also, lead impurities can accelerate corrosion.

In this paper, the conceptual design of a small lead-cooled nuclear reactor intended to replace diesel-power in off-grid applications is presented. In a vessel of dimensions making it transportable ...

FeCrAl alloys are proposed candidate materials for liquid lead applications. Chromium is needed to assist the formation of a protective alumina layer, albeit has to be limited to avoid alpha' precipitation. Reactive elements (RE) improve oxidation properties, but little is known about the RE effects at lower temperatures. An alloy matrix based on Fe-10Cr-4Al (wt%), with varying Zr, Y and Ti contents, was exposed to liquid lead up to 1 year in the temperature interval of 450-550 A degrees C. It was found that the formation of protective alumina was dependent on the RE/carbon ratio. All alloys with ratios lower than unity showed poor oxidation properties due to the formation of Cr-carbides in the metal-oxide interface. A sufficiently high amount of Zr and Ti was shown to significantly improve the oxidation properties at both temperatures. The positive effect is related to the suppression of Cr-carbides by addition of stronger carbide formers. QC 20171010

Comments on the paper "Copper in ultrapure water, a scientific issue under debate" by M. Ottosson, M. Boman, P. Berastegui, Y. Andersson, M. Hahlin, M. Korvela, and R. Berger

The aim of the work has been to study the corrosion resistance of a new low alloyed experimental FeCrAl steel, with the potential use as corrosion barrier in high temperature lead based energy applications. The exposures were conducted in liquid lead at 800 °C and 900 °C, with controlled oxygen environment, for up to 1760 h. The results demonstrate that the new experimental alloy had formed a protective oxide in both exposures, with no indications of lead penetration. The alloy showed better corrosion properties than that of the reference materials: Kanthal APM™, Kanthal APMT™ and AISI 316L. This indicates that the ductile Fe–10Cr–4Al-RE steel can be used as a corrosion barrier in liquid lead based clean energy applications, operating at very high temperatures.

The aim of this paper is to present a critical analysis of existing methodologies, approaches and strategies used to develop materials systems and coatings for uses in extreme environments. The extreme or harsh conditions encompass a large variety of in-service forms such as: extreme temperatures, abrasion, corrosion, impact and radiation that can exist in various applications such as those associated with aerospace and aeronautical engineering, land and marine transport, manufacturing machinery, and even microelectronics products. This article describes how working environment and required service performance of a particular part or structure could affect the choice of materials and surfaces to which it is composed. In addition, the paper explains the relevance that abusive working environments have for industry, especially relating to their costs, being followed by an overview of surface deposition approaches that are currently popularly used to improve performance of mechanical devices that need to combat adverse conditions. Finally, a material system and three kinds of protective coatings that could be used in applications in extreme conditions are described. The critical review is an outcome of the strategic review from the EU H2020 SUPERMAT project which deals with materials and manufacture for the products/structural parts used in extreme conditions.

Iron-Chromium-Aluminium (Fe-Cr-Al) alloys have been widely investigated as candidate materials for various nuclear applications. Albeit the excellent corrosion resistance, conventional Fe-Cr-Al alloys suffer from alpha-alpha' phase separation and embrittlement when subjected to temperatures up to 500 degrees C, due to their high Cr-content. Low-Cr Fe-Cr-Al alloys are anticipated to be embrittlement resistant and provide adequate oxidation properties, yet long-term aging experiments and simulations are lacking in literature. In this study, Fe-10Cr-(4-8)Al alloys and a Fe-21Cr-5Al were thermally aged in the temperature interval of 450-550 degrees C for times up to 10,000 h, and the microstructures were evaluated mainly using atom probe tomography. In addition, a Kinetic Monte Carlo (KMC) model of the Fe-Cr-Al system was developed. No phase separation was observed in the Fe-10Cr-(4-8)Al alloys, and the developed KMC model yielded results in good agreement with the experimental data.

One way of reducing the furnace wall corrosion is to lower the temperature of the wall by reducing the boiler pressure. To test this, four coupons of 16Mo3 were exposed in the furnace wall of a waste wood fired boiler for 1075 h. The temperatures of the samples were individually controlled in the range 280–410°C. The corrosion rates and corrosion mechanism were investigated. The deposits were analysed by XRD and SEM/EDS. The corrosion fronts were studied by focused ion beam milling (FIB)/EDS. The environment was modelled by Thermo-Calc. The amount of potassium and chlorine in the deposit decreased with decreasing temperature. The FIB sections showed a distinctive iron chloride layer at the corrosion front, with an outer layer of iron oxide. The corrosion rate decreased with decreasing metal temperature, but the boiler pressure needs to be reduced to a low level to achieve this, which is not beneficial for the electrical efficiency and therefore not a viable way of reducing corrosion.

The expertise, main experimental facilities and some selected results of the EU SUPERMAT Consortium are described, showing the importance of integrating modelling and simulation, fast sintering and coating technologies and specific characterisation techniques for obtaining high temperature ceramics, oxide dispersion strengthened (ODS) steels or Li-ion batteries with controlled properties for extreme environmental applications. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Five experimental FeCrAl-RE alloys have been exposed up to 10,000 h in stagnant liquid Pb at 550 C. The test matrix consisted of three 10 wt.% Cr alloys, with an Al content ranging from 4 to 8 wt.% (10Cr-4Al, 10Cr-6Al and 10Cr-8Al), one alloy without additions of reactive elements (RE) (10Cr-6Al), and one reference alloy with 21 wt.% Cr and 5 wt.% Al (21Cr-5Al). The evaluation showed a clear difference in oxidation properties, and it was possible to divide the alloys into two distinct groups. A critical Al concentration in the interval of 4-6 wt.% at the given RE content was required to form a thin protective oxide. However, the absence of RE addition in one of the two 10Cr-6Al alloys resulted in a significant reduction in oxidation resistance, comparable with 10Cr-4Al. None of the alloys were severely corroded, however Pb penetrated to a relatively large extent into the porous oxide of the low performing alloys. A 100 nm thick oxide scale, partly consisting of alumina (Al2O3), was observed for the high performing 10Cr-6Al alloy. The Fe10CrAl-RE alloys showed overall very good corrosion resistance and are hence a promising new alloy category for liquid Pb applications. (C) 2013 Elsevier B.V. All rights reserved.

The use of waste wood as a fuel in power plants is becoming more widespread in Europe, because it is a renewable energy source with a lower cost than forest fuel. However it is more corrosive than ...

New insights are presented on the speciation of surface oxide phases on fine inert gas atomised (GA

Due to an expected temperature increase of the exhaust gases in heavy-duty engines in order to meet future emission regulations, there is a need to develop materials that can operate at higher temperatures. The exhaust manifold in the hot end of the exhaust system is specifically affected since the most common material today, SiMo51, is already operating close to its limits. Accordingly, the effects of Cr and Ni-additions on the high-temperature corrosion resistance of this material in air and exhaust gases were examined. It was found that the addition of 0.5 and 1 wt% Cr improved the oxidation resistance in air at 700 and 800 °C by the formation of an SiO2 barrier layer as well as a Cr-oxide at the oxide/metal interface. However, no Cr-oxide was detected after exposure to exhaust gases, probably due to a water vapor-assisted evaporation of Cr from the oxide. The addition of 1 wt% Ni resulted in a deteriorated SiO2 barrier layer and reduced oxidation resistance.

Electron Backscatter Diffraction (EBSD) studies clearly revealed a different crystallographic structure of the smallest particle size fraction of gas-atomized AISI 316 L stainless steel powder (&lt ...

According to a current concept, copper canisters of thickness 0.05 m will be safe for nuclear waste containment for 100,000 years. We show that more than 1 m copper thickness might be required for 100,000 years durability based on water exposures of copper for 20 h, 7 weeks, 15 years, and 333 years. An observed evolution of hydrogen which involves heterogeneous catalysis of molecular hydrogen, first principles simulations, thermodynamic considerations and corrosion product characterization provide further evidence that water corrodes copper resulting in the formation of a copper hydroxide. These findings cast additional doubt on copper for nuclear waste containment and other important applications.

This paper gives an overview of the different processes of metal dusting (MD) that operate on low and high alloyed iron and nickel base alloys exposed in CO+H2–containing environments with or without water vapour. MD of pure metals like iron and nickel occur with a solely carbon-induced corrosion mechanism. However, in high alloyed materials with strong oxide formers such as Cr and Al, a more complex MD-process takes place which involves both carbon and oxygen in close collaboration. The “alloyed” carbides, i.e normally Cr-containing carbides, formed in such materials are thermodynamically stable with respect to the carbon activity. However, in the reaction front of a MD-pit with non-protective spinel oxide, they destabilise and dissolve due to the influence of the low oxygen activity determined by CO-dissociation. Based on recent results in the field of MD a chart with tentative MD mechanisms is presented as a function of alloy composition and temperature.

For long time it is known that protons in aqueous solutions have a detrimental effect on metallic materials. Relatively recently, it has also been observed in aqueous solution that the pitting corrosion resistance of Cr, stainless steel 304 and 310 decreases and the anodic dissolution rate increases due to the presence of hydrogen in the metal. In gas phase a high oxidation rate has been observed for hydrogen containing Cr and Fe. Hydrogen in the substrate can also enhance the oxidation of Fe in SS 316 and As in GaAs. All these results suggest enhanced dissolution in aqueous solution and enhanced oxide growth at the oxide/gas interface in gas phase oxidation due to hydrogen promoted outward-transport of substrate components. A possible mechanism for such out-transport is an increased metal ion diffusivity in the metal-oxide due to a high abundance of metal ion vacancies generated by hydrogen. In contrast to all the above examples, also positive effects of hydrogen have been identified under certain conditions. In an attempt to understand both the negative and the positive effects the concept of a beneficial, balanced oxide growth is used. In this concept a certain amount of hydrogen can be beneficial in the oxidation by improving the balance between oxygen-ion and metalion transport, leading to more dense and protective oxides. Depending on the temperature, H2 in air is considered as either a sink or a source for hydrogen in materials.

A high-performance commercial alumina-forming Ni-base alloy was studied after a 2 years field exposure at 540 degrees C in a methanol plant with a gas composition of 10-20%CO and 20-40%H2O, with so ...

In the last few years, there has been a move away from burning fossil fuels through the co-utilisation of biomass and coal and finally to 100% biomass such as wood and waste wood products. Unfortun ...

The primary intention with this Doctoral thesis is to fillin the knowledge gaps and raise the level of understandingregarding the different metal dusting mechanisms in general andexplain the process in detail for high alloyed materials.Considerable effort is put into identifying the driving forcesand elucidating the diffusional processes in metal dusting. The results are based on a series of long-term laboratory exposures of stainless steels and high-performance commercial alumina-forming Fe- and Ni-base alloys in synthesis gasmixtures, plus a separate shorter study on ultra pure iron. ANi-base alloy was also investigated after a two years field exposure in a methanol plant. Post exposure metallographic examinations and analysis aswell as thermodynamic calculations were made in order toidentify and describe the operating metal dusting mechanisms.Two main mechanisms were previously used to explain metaldusting, one on the basis of decomposition of metastable carbides (Type I) the other on graphite formation (TypeII). A new metal dusting mechanism has been identified in this Thesis which appears on high alloyed steels and Ni-base alloys,an active corrosion induced by carbon and oxygen, denoted TypeIII. Both the mechanisms and the type of corrosion products were consistent with the thermodynamic conditions of the material under the influence of a carbon and oxygen gradient.It was shown that this mechanism not only accelerates the metaldusting process, in fact, it determines the overall metaldusting kinetics on stainless steels and Ni-base alloys. Another feature, which may occur at temperatures where metalbulk and even static grain boundary diffusion is too slow forexplaining the metal dusting corrosion process, was identifiedon a Ni-base alloy. It involves a fast growing cellular structure with discontinuous precipitated carbides whichprovides fast metal dusting kinetics by the Type IIImechanism. A Type IV metal dusting mechanism, continued fragmentationby graphitization until nano-sized particles are formed andcatalyse carbon nanotube formation is also described. Thesteady state process and the driving force for metal dusting onpure iron was identified and described. With these additional processes it is now possible to extendour understanding of the metal dusting processes to a widerange of engineering alloys.

The mechanisms of metal dusting as it appears on different ferritic stainless steels and pure iron have been described in detail. A mechanism for metal dusting (MD) of chromia-forming as well as al ...

A mechanism for metal dusting of chromia-forming stainless steels is proposed, based on results from laboratory exposures of 304L stainless steel at 650 degreesC for 1000 h in a synthesis gas low i ...

The normal grain sized 153MA-sample experienced an almost linear weight gain curve in the sulphidizing environment while modified materials, with a finer grain size or cold worked structure, displayed more parabolic behaviour and lover weight gains. These effects may be related to more effective Cr-diffusion in the modified samples with a higher Cr-grain boundary diffusion in the fine grain-sample and a higher Cr-bulk diffusion rate in the cold worked sample. The sand blasted sample performed exceedingly well with a thin protective oxide layer compared to the etched and ground samples which both suffered significant weight loss and spalling. The deformed surface structure on the sand blasted sample enhances the Cr-bulk diffusion thus promoting a protective Cr-rich oxide formation.

This paper considers the corrosion of copper in water by: (1) short term, open system weight measurements and (2) long term, closed system immersion in distilled water (13,800 h) without O2 at 21–55 C. In the latter experiments, the hydrogen gas pressure is measured above the immersed copper and approaches ~10-3 bar at equilibrium. This pressure is mostly due to copper corrosion and greatly exceeds that in ambient air. Accordingly, this measured hydrogen pressure from copper corrosion increases with temperature and has the same dependency as the concentration of OH- in the ion product [OH-] [H+].

Certain elements, including noble metals, are identified to influence corrosion behavior of many metals in high-temperature water/steam and O-2. We have previously reported effects of porous Pt coa ...

adsorption. They argue that OH is extremely rare in waterand, therefore, is not valid to corrosion. We beg to differ. Ifthe formation of CuOH—in whatever structural form itmight appear—is thermodynamically favourable, the sys-tem will end up in that state. The concentration of OH willbe maintained by the removal of H. Whether the access tothe surface will be promoted by structural changes (at thenanoscale, for example) remains an open question. How-ever, the stability of CuOH as computed in our paper isclear and complies with all the rules of thermodynamics,including the first law. There can be many other CuOHstructures that are not stable in relation to copper oxide andwater, one of which is shown by the authors of the Com-ment. However, it is enough that just one is stable, and wehave shown that such a possibility does exist. Of course,when the concentration of particles is low and formation ofstructures with an abundance of surface is needed, thekinetics of corrosion might be slow. This is when experi-ment tells us about the kinetics. The possibility ofcorrosion is, however, in full compliance with the existingthermodynamics and therefore we see our simulations asmeaningful in the context of the current discussion. Ofcourse, any theoretical work, like a simulation, is onlymeaningful if compared to valid experimental results andcan hardly be of any persisting value without any agree-ment in such a comparison.Liquid pure water is obviously overall neutral with adefined ion product of H

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We have studied copper corrosion in a system comprised of deionized water, absolute pressure gauges, and a palladium membrane. A transition from O-2-consuming to H-2-evolving copper corrosion is ob ...

New ductile experimental FeCrAl alloys, based on the composition of Fe–10Cr–4Al, were exposed to stagnant liquid lead at 750 °C for up to 1970 h. Two exposures with different test conditions were performed: one with addition of oxygen (as H2O) to the liquid lead and one without. The experimental alloys showed generally good oxidation and self-healing properties. The exposures showed that this specific category of steels has the potential to operate in liquid lead at very high temperatures with only minor oxidation. With this new material development, new energy technologies such as the CSP plants may be able to utilize liquid lead at very high temperatures as heat transfer fluid, thus achieving increased thermal efficiency.

A primary concern in the development of accelerator-driven systems (ADS) with liquid leadbismuth eutectic (LBE) spallation target and Gen-IV lead-cooled fast reactors (LFRs) is the compatibility of ...