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Ítem Acceso Abierto Fe-Al Intermetallic Phases Present in Fe Aluminide Coatings(Universidad de Las Palmas de Gran Canaria, 2011-09-09) Agüero, Alina; González, Vanessa; Gutiérrez del Olmo, Marcos; Muelas Gamo, RaúlIron aluminide coatings are known to protect steels at elevated temperatures in diverse industrial environments. Depending on the Al content of the Fe-Al phase, a protective Al2O3 scale can be formed and maintained and the coatings are relatively stable up to approximately 900º C. At higher temperatures, Al inwards diffusion causes impoverishment of Al at the surface until it reaches a critical concentration below which the protective oxide will not form. Depending on the coating composition an Al content of 4 to 8 wt. % seems to be sufficient to maintain the protective scale [1-3]. Among the diverse coating deposition techniques, the application of slurries is one of the most economical, practical and versatile. Aluminide coatings have been generated by applying an Al slurry followed by heat treatment which depends on the substrate. For instance, it has been shown that on ferritic steels, deposition of an Al slurry followed by heat treatment at 700º C for 10 h generates a complex aluminide coatings composed of several intermetalllic phases including FeAl3, Fe2Al5 and FeAl (see figure 1). Under the coating, AlN acicular precipitates can form within the substrate, if the substrate contains sufficient N (≥ 0.01 wt. %) [4-6]. The coatings exhibit thickness-through cracks probably due to brittleness of the Fe2Al5 phase and to thermal expansion mismatch between the different phases. Figure 1: SEM cross sections of an "as deposited" Al slurry coating on P92 followed by heat treatment for 10 h at 700º CÍtem Acceso Abierto A direct comparative study of the corrosion behaviour of Si-free and Si-rich slurry aluminide coatings in molten carbonate melts(LNEG Laboratorio Nacional de Energia e Geologia, 2022-11-24) Audigié, Pauline; Sergio, Rodríguez Catela; Agüero, Alina; Pedrosa, Fátima; Paiva, Teresa; Diamantino, TeresaABSTRACT: This study is focused on the evaluation of the hot corrosion behaviour of two low-cost slurry aluminide coatings with and without Si addition deposited on ferritic-martensitic steels, comparing them with uncoated steel, after 1000-h of exposure to Li, K, Na molten carbonates at 650ºC, under static and dynamic conditions with a high linear velocity (1.3 m/s). Both coatings evidenced a high performance increase in comparison with uncoated substrates after exposure in both conditions. Both coatings behaved in a similar way according to the gravimetric results. However, after dynamic exposure, the Si-free aluminide maintained its morphology and composition after 1000 h with α-LiAlO2 as the only corrosion product while the Si-rich coating showed a higher attack extent in the outer part and developed a large quantity of voids at the coating/substrate interface, leading to substrate corrosion.Ítem Acceso Abierto Hot Corrosion and Mechanical Performance of Aluminide Coated Austenitic Steel(Thermal Energy Storage Materials, Media, and Systems, 2025-11-18) Oger, Loïc; Agüero, Alina; Audigié, PaulineThe present study aims at improving coatings to allow higher operating temperatures – up to 700 °C – while resisting hot corrosion in future heat transfer fluids and storage systems for CSP technology. An aluminide coating was produced onto a 347H austenitic alloy to resist Li-Na-K molten carbonate corrosion at 700 °C. Multiple surface preparations were investigated and, after optimization, a new diffusion heat treatment was selected. A homogeneous 3-layer coating was formed with Al content reaching up to 69 at.% at the top surface. Corrosion was significantly decreased by the coating compared to the uncoated material. After 500h-exposure, a 100 µm-thick multi-layered and non-adhesive alkali elements rich oxide formed at the surface of uncoated 347H alloy. On the contrary, the coated material preserved its morphology and a mix of α-LiAlO2 and γ-LiAlO2 formed on the top coating. From the mechanical perspective, local hardness measurements highlighted a broad variation along the different layers of the coating. 3-point bending tests showed that deformation in the plastic domain was required to cause crack formation. Cracks remained in the two outermost layers of the coating and did not reach the underneath substrate.Ítem Acceso Abierto Experience with 9Cr3W3CoVNbBN base material and crosswelds at 650°C for implementation in USC power plants(National Institute for Materials Science, Tsukuba , Japan, 2009-06-14) Mayr, Peter; Mendez Martín, Francisca; Holzer, Iván; Agüero, Alina; González, Vanessa; Baumgartner, Susanne; Cerjak, Horst HannesThis manuscript gives an overview on recent developments of a martensitic steel grade based on 9Cr3W3CoVNb with controlled additions of boron and nitrogen. Alloy design by thermodynamic equilibrium calculations and calculation of boron-nitrogen solubility is discussed. Two melts of a 9Cr3W3CoVNb steel were produced. The oxidation resistance was examined at 650°C in steam atmosphere. The alloy exhibited high resistance to steam oxidation at 650°C for at least 5.000 hours of exposure. Microstructural evolution during welding within the heat-affected zone was investigated by physical weld simulation, thermo-dilatometry and in situ X-ray diffraction using high energy synchrotron radiation. The heat-affected zone microstructure is characterized by optical microscopy. Two multilayer welds, one with a nickel based filler and one with a newly developed flux cored filler of matching chemical composition, were fabricated. All weldability experiments showed that within the heat-affected zone the initial base material microstructure is retained to a large extent. The formation of a uniform fine-grained heat-affected zone region is suppressed. Uniaxial creep tests of base material, weld metal and crossweld specimens were started at different levels of stress at 650°C. Up to the established maximum testing time of 20.000 hours, the base material shows significant improvement compared to standard 9 wt. % Cr grades P91 and P92. Crossweld specimens show an improved strength level, higher than that of grade P92 base material. Preliminary results of an extensive testing program on a 9Cr3W3CoVNbBN steel show significant improvement compared to the state-of-the-art 9 wt. % Cr martensitic steel grades.Ítem Acceso Abierto Improved Creep and Oxidation Behavior of a Martensitic 9Cr Steel by the Controlled Addition of Boron and Nitrogen(University of Liege, 2010-09-27) Mayr, Peter; Holzer, Iván; Mendez Martín, Francisca; Albu, Mihaela; Mitsche, Stefan; González, Vanessa; Agüero, AlinaÍtem Acceso Abierto Oxidation performance of high temperature steels and coatings for future supercritical power plants(University of Liege, 2010-09-22) Auerkari, Pertti; Salonen, Jorma; Toivonen, Aki; Penttilä, Sami; Juha, Häkkilä; Agüero, Alina; Gutiérrez del Olmo, Marcos; Muelas Gamo, RaúlThe operating efficiency of current and future thermal power plants is largely dependent on the applied temperature and pressure, which are in part limited by the internal oxidation resistance of the structural materials in the steam systems. Alternative and reference materials for such systems have been tested within the COST 536 (ACCEPT) project, including bulk reference materials (ferritic P92 and austenitic 316 LN steels) and several types of coatings under supercritical combined (oxygen) water chemistry (150 ppb DO) at 650ºC/300 bar. The testing results from a circulating USC autoclave showed that under such conditions the reference bulk steels performed poorly, with extensive oxidation already after relatively short term exposure to the supercritical medium. Better protection was attained by suitable coatings, although there were clear differences in the protective capabilities between different coating types, and some challenges remain in applying (and repairing) coatings for the internal surfaces of welded structures. The materials performance seems to be worse in supercritical than in subcritical conditions, and this appears not to be only due to the effect of temperature. The implications are considered from the point of view of the operating conditions and materials selection for future power plants.Ítem Acceso Abierto Steam oxidation behavior of high strength newly developed ferritic/martensitic steels at 650º C(2010-05-24) Agüero, Alina; González, Vanessa; Mayr, Peter; Spiradek, KrystinaÍtem Acceso Abierto A slurry coating for Cd replacement for aircraft components(Mondragon Unibertsitatea, 2008-07-25) Agüero, Alina; Blanco, C; Gutiérrez del Olmo, Marcos; García Martínez, MaríaÍtem Acceso Abierto Tribolab: An experiment on space tribology(European Space Agency (ESA), 1998-11-05) Gómez Elvira, J.; Oñate, J. Ignacio; Marcos, J.; Rowntree, R.; Agüero, A.The accurate knowledge of the com:pIex behavior of lubricant systems, both solid and liquid, is a fundamental requirement for the reliable operation in orbit of spacecraft mechanisms. Modem spacecraft, of all types, proliferate with mechanisms whose predictable operation is mandatory. In flight a spacecraft mechanism must develop its function under a quite hostile environment, which is made up mainly by space radiation, extreme thermal conditions, vacuum, atomic oxygen and mechanical effects like microvibrations. All those conditions are impossible to simulate simultaneously on ground. Some tribometers flown in the past in order to correlate the flight and ground tests results showed a good correlation of data for simple friction and wear of bulk materials and surface coatings. Nevertheless, new promising materials and processes, never flown before, will be implemented in the experiment to know its behavior against the above mentioned environment and laying stress in }igravity conditions.Ítem Acceso Abierto Quasicrystalline Materials as Thermal Barrier and Hot Corrosion Resistant Coatings(University of Toronto, 1999-10-20) Agüero, A.; Álvarez, J.; García de Blas, Javier; Sánchez, A.; Villar, I.Ítem Restringido Coatings For Steam Power Plants Under Advanced Conditions(European Cooperation in Science and Technology, 2002-09-12) Agüero, A.; Muelas Gamo, Raúl; Scarlin, B.; Knodler, ReinhardÍtem Restringido Cyclic Oxidation of Steam Pre-oxidized MCrAlY and Ni Aluminide Coatings(Turbine Forum, 2004-08-25) Agüero, A.; Román Gárate, Alicia; Gutiérrez, MarcosSignificant attention has been paid to high temperature oxidation resistant coatings such as overlay MCrAlYs and diffusion Ni aluminide coatings to protect superalloys in both aeronautic and gas turbine components. Both coatings behave as Al reservoirs in order to form a protective Al2O3 layer. Said layer is very stable but grows with exposure time and will also tend to spall due to thermal cycling. Both types of coatings are also employed as bond layers for thermal barrier ceramic coatings (TBCs), which are employed to maintain a lower surface temperature for refrigerated turbine components. The bond coating has a dual function as it reduces the thermal expansion coefficient mismatch between the ceramic layer and the superalloy, and protects the superalloy from environmental degradation due to air as well as other contaminants that will permeate through the porous ceramic top layer. The main cause of failure of TBCs is related to spalling of the ceramic top layer due to stresses resulting from the Al2O3 growth at the bond coating-thermal barrier interface. It has been shown that bond coat pre-treatment prior to the TBC deposition has a strong influence on the oxidation resistance of these coatings. Moreover, recent results by C. Zhou and collaborators have indicated that steam present in air will significantly increase the oxidation rate of TBCs (with MCrAlYs as bond coating) and the cause is attributed to the formation of thick porous mixed oxides related to the presence of steam. The authors suggest that H dissolved into the initially formed oxides enhance Ni and Cr ion outwards diffusion.Ítem Acceso Abierto Latest Results in the Development of Steam Resistant Coatings for New Generation High Temperature Supercritical Steam Plants(Turbine Forum, 2006-03-12) Agüero, A.; Muelas Gamo, Raúl; Gutiérrez, MarcosÍtem Acceso Abierto Development and Validation of Advanced Oxidation Protective Coatings for Super Critical Steam Power Generation Plants(Grafische Medien, 2006-07-06) Scheefer, M.; Bernard Henderson, Michael; Agüero, Alina; Allcock, B.; Norton, B.; Tsipas, D. N.; Durham, R.; European Commission (EC)Increasing the efficiency of coal-fired power plant by increasing steam temperatures and pressures brings benefits in terms of cheaper electricity and reduced emissions, particularly CO 2 . In recent years the development of advanced 9%Cr ferritic steels with improved creep strength has enabled power plant operation at temperatures up to 600 -620ºC such that these materials are currently being exploited to construct a new generation of advanced coal-fired plant. However, the move to higher temperatures and pressures creates an extremely hostile oxidising and errosive environment. To enable the full potential of the advanced 9%Cr steels to be achieved, it is vital that protective coatings are developed, validated under high pressure steam environments and applied successfully to candidate components from the high pressure steam path. This paper reviews recent work conducted within the Framework V Brite EuRam project "Coatings for Supercritical Steam Cycles" (SUPERCOAT) to develop and demonstrate advanced slurry and thermal spray coating technologies capable of providing steam oxidation protection at temperatures in excess of 620°C and up to 300 bar pressure. The programe of work described has demonstrated the feasibility of applying a number of candidate coatings to steam turbine power plant components and has generated long-term steam oxidation rate and failure data that underpin the design and application processing work packages needed to develop and establish this technology for future and retrofit plant.Ítem Restringido Characterization of Tribological Quasicrystalline Composite Coatings(Deutscher Verband für Schweisstechnik, 2002-03-06) Román, A.; Agüero, A.; De Miguel, C.; García de Blas, Javier; Longo, Federico; Muelas Gamo, Raúl; Sánchez, A.Quasicrystalline (QC) alloys constitute a family of materials with low coefficient of friction, high hardness, and high yield strength under compressive stress. This paper examines the characteristics of QC composite coatings deposited by LPPS and HVOF spraying. It compares the coatings based on phase distribution and microstructure. Both compositions studied are extremely wear resistant, but their friction properties require further development. Paper includes a German-language abstract.Ítem Acceso Abierto Coatings for Protection of High Temperature New Generation Steam Plant Components: A Review(Grafische Medien, 2006-04-06) Agüero, A.Ítem Acceso Abierto Behaviour of coated and uncoated ferritic steels under isothermal and cyclic steam oxidation conditions(VTT, 2007-06-14) Agüero, Alina; González, Vanessa; Gutiérrez, M.Next generation steam turbines are expected to operate at 600-650°C and at these temperatures, currently available high strength ferritic-martensitic steels need to be coated to prevent oxidation. Slurry deposited aluminide coatings have shown excellent performance up to 650°C under isothermal conditions. The behaviour of these coatings as well as that of uncoated P92 under thermal cycling conditions has been studied both in steam and in air at 650°C. The tested specimens were characterized by field emission scanning electron microscopy. A comparison with isothermal steam oxidation has been established. In cyclic oxidation, evidence of scale spallation from uncoated substrates was observed at shorter exposure times than for specimens tested under isothermal conditions. In the coated specimens, cracks originally present in the "as deposited" coating did not propagate or become sites of preferential oxidation during isothermal steam testing. However, the cracks widened and propagated causing substrate oxidation when the specimens were tested by thermal cycling in steam or in air.Ítem Restringido Applications of Quasicrystalline materials as Thermal Barriers in Aeronautics and Future Perspective ofUse for these Materials(Springer, 1998-05-05) Sánchez, A.; García de Blas, Javier; Algaba, J. M.; Álvarez, J.; Vallés González, Pilar; García Poggio, M. C.; Agtiero, A.Quasicrystalline materials (QCs) have very interesting properties which make them good candidates to be used as coatings resistant to wear, high temperature oxidation, corrosion, etc. the potential application of AI71Co13Fe8Co8 (QC1), a quasicrystalline approximant alloy, as a thermal barrier coating (TBC) for components of aeronautical and power generation turbines was explored in our laboratories and the results are presented in this paper. QC1 is stable at I 1000°C and has a thermal conductivity similar to that of yttria stabilized zirconia (YSZ), the most commonly used material for TBCs. QC1 powders were low pressure plasma sprayed on IN100 superalloy and coatings of excellent quality were obtained after a series of optimization experiments. the “as deposited” coatings were characterized by XRD, SEM and TEM and the results indicated that the coatings retained the same microstructure and phase composition as the bulk material. However, when coated specimens were heat treated at 950°C, interdifussion between coating and substrate took place resulting in the transformation of the QC approximant phase. To avoid or retard this process, the effect of several diffussion barrier layers, deposited between substrate and coating, was studied and the results showed that some of these barriers were quite efficient in slowing the diffusion process. Extensive cyclic oxidation and hot corrosion studies were carried out, showing promising results for this new type of TBC coatings. A short term ground engine test was carried out with coated blades.Publicación Acceso Abierto RAISELIFE project extends the lifetime of functional CSP materials(AIP Publishing, 2022-05-12) Sutter, Florian; Binyamin, Yaniv; Zoschke, T.; Fernández García, Aránzazu; Naamane, S.; Galetz, M.; Reoyo Prats, R.; Pérez Trujillo, Francisco Javier; Aglüro, Alina; Orioli, F.; Piron, Javier; Mandler, D.; Attout, A.; Caron, Simon; Wette, J.; Sánchez, Ricardo; Morales, Angel; Hildebrandt, C.; European Commission (EC)The RAISELIFE project was conducted from April 2016 until March 2020 and was funded within the H2020 program of the European Commission (Grant 686008). The project aimed at developing novel materials with extended lifetime and performance for parabolic-trough and solar tower CSP plants and thereby reducing electricity generation costs. In order to assess the expected durability of the novel materials, improved accelerated aging and qualification methods simulating in-service conditions in different climates were developed. The project brought together a broad consortium formed of industry partners, SMEs and research institutes of the CSP and material science sector. This paper summarizes the main developments and takeaways from the RAISELIFE project.
