(Aeronáutica) Artículos

URI permanente para esta colecciónhttps://digitalpro.inta.es/handle/20.500.12666/48

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10,000 h molten salt corrosion testing on IN617, uncoated and aluminide ferritic steels at 580 ºC
(Richter C., 2020-12) Agüero, Alina; Audigié, P.; Rodríguez, Sergio; European Commission (EC)
Long term testing of two ferritic-martensitic steels (P91 and VM12-SHC) with and without slurry deposited aluminide coatings containing 20 wt.% of Al at the surface was carried out by exposing these materials to the Solar Salt, a eutectic mixture composed of 60 % NaNO3 - 40 % KNO3 at 580ºC. This salt is currently used in operating thermal solar power plants as heat transfer and storage fluid. Tubes made of expensive Ni based alloys are employed to mitigate corrosion. The tested uncoated ferritic materials exhibited very high corrosion rates developing thick, easily detached scales. IN617 was also tested as a reference and experienced very low corrosion up to 5,000 h, but after 10,000 h a 50 ȝm thick, mostly NiO scale had developed with Na0.6CoO2 crystals deposited on top. There was also evidence of significant Cr depletion at the alloy surface. Carcinogenic CrVI was found in the Solar Salt melt in which the three uncoated alloys were immersed. In contrast, the two coated ferritic steels did not show evidence of degradation after 10,000 h and the most significant microstructural change was the development of a very thin protective NaAlO2 layer on their surface. An industrial process to deposit these coatings on the inner surfaces of pipes has already been developed.
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Al Slurry Coatings for Molten Carbonate Fuel Cell Separator Plates
(Scientific.Net, 2001-01-20) Agüero, Alina; García, M. C.; Muelas Gamo, Raúl; Sánchez, A.; Pérez, Francisco J.; Duday, David; Hierro, M. P.; Gómez, Consuelo
The corrosion behaviour of Al slurry coated AISI 310 stainless steel, with and without diffusion heat treatment, was investigated as a wet seal material for molten carbonate fuel cell (MCFC) at 650°C. The results were compared with IVD Al coated AISI 310. Characterization of the samples before and after exposure to the eutectic 62 mol% Li2CO3-38 mol% K2CO3 mixture at 650°C for 1000 h by SEM-EDS and XRD was carried out. The presence of LiAlO2 on the coated samples was confirmed by XRD. The slurry Al-coated stainless steels performed at least as well as the IVD Al coating.
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Comparison between field and laboratory steam oxidation testing on aluminide coatings on P92
(Wiley online library, 2011-01-12) Agüero, Alina; González, V; Gutiérrez del Olmo, Marcos; Knödler, R; Straub, S; Muelas Gamo, Raúl; Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Steam oxidation has become an important issue for steam power plants as operating temperatures increase from the current 550 to 600–650 °C. For the last 10 years several groups have been carrying out steam oxidation testing of both uncoated substrates and coatings in the laboratory. On the other hand, field testing results are very scarce. In this paper, a comparison of laboratory steam oxidation testing with field test results carried out by Alstom at the Kraftwerk Westfalen power station located in Hamm, Germany will be presented. Both slurry deposited aluminide coatings and uncoated P92 steel have been included in the study. Under steam (atmospheric pressure) and isothermal conditions in the laboratory at 650 °C, spallation of oxides formed on ferritic steels occurs after significantly longer time when compared to exposure to real operating conditions. Oxide spallation results in serious damage in steam power plants by obstructing heat exchanger tubes, erosion of valves and turbine blades, etc. Moreover, the thickness of the oxide scales formed under field testing conditions is significantly higher after similar exposure. On the other hand, aluminide coated P92, which exhibit thickness through cracks, have shown to be stable in the laboratory for up to 60 000 h at 650 °C under steam, without evidence of crack propagation. However, field test results indicate that some degree of crack propagation occurs but without causing substrate attack up to 21 700 h of exposure. Moreover, the aluminium oxide observed in both laboratory and field tested specimens is different.
Acceso Abierto
Comparison between pilot and lab scale testing of aluminide coated and uncoated ferritic steels under oxy-fuel and coal/thistle co-firing conditions
(Elsevier, 2022-11-25) Gutiérrez, M.; Illana, Andrea; Bahillo, Alberto; Benito, Manuel J.; García Martín, G.; Pérez Trujillo, Francisco Javier; Agüero, Alina; European Commission (EC); Universidad Complutense de Madrid(UCM)
The present study compares the biomass corrosion behavior of two diffusion aluminide coating obtained by slurry application, which were deposited on two low-chromium content steels, ferritic-martensitic P92 (8.7 wt% Cr) and ferritic T22 (2 wt% Cr). Their performance degradation was conducted under an oxy-fuel combustion environment for both coated and uncoated materials both under laboratory conditions and in a pilot plant burning thistle for 500 h. Exposures were carried out in the laboratory at two different temperatures, 600 °C and 650 °C, under a model atmosphere consisting of 60 % CO2, 30 % H2O, 8 % O2, bal.% N2 (in vol%), 500 vppm HCl and 2 vppm SO2. The pilot plant used a mixed fuel of 60 wt% coal and 40 wt% thistle that was burnt and the samples were exposed to a temperature range of 600–620 °C. After testing, the results revealed that the aluminide-coated materials exhibited a very high resistance under both extreme scenarios, with a variable protective character related to their Al content. On the contrary, uncoated material exhibited severe degradation, in particular T22. Microstructural and morphological studies showed up similar corrosion patterns and products on coated and uncoated materials for both testing environments.
Restringido
Cyclic oxidation and mechanical behaviour of slurry aluminide coatings for steam turbine components
(Elsevier, 2007-04-02) Agüero, Alina; Muelas Gamo, Raúl; Gutiérrez del Olmo, Marcos; Van Vulpen, R.; Osgerby, Steve; Banks, J. P.
The excellent steam oxidation resistance of iron aluminide coatings on ferritic steels at 650 °C has been demonstrated both by laboratory tests and field exposure. These coatings are formed by the application of an Al slurry followed by diffusion heat treatment at 700 °C for 10 h. The resulting microstructure is mostly composed of Fe2Al5 on top of a much thinner FeAl layer. This coating exhibits perpendicular cracks due to thermal expansion mismatch between coating and substrate. However, these stress relieving cracks do not seem to have an effect on the mechanical properties of the substrate. Cyclic oxidation, creep resistance and TMF testing of these coatings at 650 °C indicate excellent performance.
Restringido
Deposition process of slurry iron aluminide coatings
(Taylor and Francis online, 2008-10-04) Agüero, Alina; Gutiérrez del Olmo, Marcos; González, Vanessa
Diffusion iron aluminide coatings prevent steam oxidation of ferritic/austenitic steels at 650°C for at least 45,000 h. These coatings are deposited by applying Al slurries followed by a diffusion heat treatment at 650°C. The quality of the coatings is very sensitive to a number of factors such as surface preparation, slurry composition and diffusion treatment temperature. A study of the effect of the different processing parameters has been performed in order to optimize the process from an industrial perspective. Moreover, most commercially available Al slurries contain different levels of Cr6+, a highly carcinogenic species, and therefore Cr6+ free slurry formulations have been prepared. In addition, re-coating after exposure has also been developed since it is not clear yet if these coatings will last the 100,000 h which is the life limit for steam power plant design. Based on these studies, processes suitable for coating real size components and re-coating steam exposed components have been developed and are presented in this contribution.
Acceso Abierto
Development and Qualification of New Solid Lubricant Coatings. A Tribology Experiment at the Tribolab onto EUTEF
(Centre national d'études spatiales (CNES), 2000-06-12) Oñate, J. Ignacio; Brizuela, Marta; García Luis, Alberto; Viviente, J. Luis; García de Blas, Javier; Agüero, Alina; Longo, Federico; Román, Alicia
A recent study has identified that a significant number of satellite failures and anomalies, including those caused during qualification testing of mechanisms, were caused by lubrication related problems. Solid lubrication is, owing to lower vapour pressures, better boundary lubrication properties, relative insensitivity to radiation effects and wider temperature range of operation, still a preferred option for a number of space mechanisms. However, actual solid lubricants wear out and do not provide effective protection for long life mechanisms. A longer life and reduced wear debris is desirable to improve mechanism reliability. The present work reports on early results on the development of a new generation of solid lubricant coatings by the use of state of the art magnetron sputtering technology and thermal spraying processes. These coatings after a proper qualification procedure under laboratory ground conditions will be finally tested at the TriboLAB instrument that will be integrated onto the EuTEF facility at the International Space Station (ISS). Metal alloyed MoS2 solid lubricant films have been produced by a magnetron sputtering PVD process. Tribotests carried out under vacuum in a ball-on-disc tribometer with MoS2 coated AISI 440C steel discs have shown very low friction coefficients of 0.01 and long endurance, in excess of 300,000 revolutions at about a max. 0.8 GPa contact stress. These films also exhibited low friction coefficients (about 0.10) and good durability under atmospheric conditions at RT and up to 50 to 60 % RH. The thick composite lubricant coatings consisting of AlCoFeCr, NiCr, Ag and BaF2-CaF2 were deposited by plasma spray and HVOF on X-750 Ni-base superalloy. These coatings have been characterised by EDS-SEM as well as hardness measurements. The best coatings from preliminary experiments have been produced by HVOF process; these show very low porosity, a more uniform phase distribution and hardness levels of 635 HV0.2. Anticipated high temperature applications of former coatings might include elevon hinges for re-usable space planes.
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Hot corrosion study of coated separator plates of molten carbonate fuel cells by slurry aluminides
(Elsevier, 2002-12-02) Pérez Trujillo, Francisco Javier; Duday, David; Hierro, María Pilar; Gómez de Castro, Consuelo; Agüero, Alina; García, M. C.; Muelas Gamo, Raúl; Sánchez Pascual, A.; Martínez, L.
The corrosion behavior of Al coated AISI 310S stainless steel by slurry and ion vapor deposition (IVD) was investigated as an electrolyte seal material in a mounted carbonate fuel cell (MCFC) at 650 °C. The results were compared with uncoated AISI 310S stainless steel and TA6V alloy. The characterization of the samples after exposure to the eutectic 62 mol.% Li2CO3–38 mol.% K2CO3 mixture at 650 °C up to 1000 h has shown the presence of LiAlO2 (coated samples), LiFeO2 and LiCrO2 (stainless steels), and Li2TiO3 (TA6V) oxides at the scale–melt interface. The electrochemical impedance spectroscopy (EIS) technique has shown high values of polarization resistances for TA6V and lower values for coated steels. The uncoated AISI 310S stainless steel have shown the lowest polarization resistance. A mechanism for the corrosion of Al-coated stainless steels in molten carbonate is proposed taking into account thermodynamic simulations, X-ray diffraction (XRD), scanning electron microscopy (SEM) characterizations, and EIS results. This proposed mechanism confirms that a slurry aluminide coating is able to improve the stainless steel behavior in molten carbonate. However, the TA6V titanium alloy is the most resistant material in molten carbonate but the Al-coated stainless steels appear as the best lifetime-cost compromise.
Restringido
HVOF coatings for steam oxidation protection
(Wiley online library, 2008-05-29) Agüero, Alina; Muelas Gamo, Raúl; González, Vanessa; Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
In the context of the European project ‘Coatings for Supercritical Steam Cycles’ (SUPERCOAT), the use of steam oxidation resistant coatings on currently available ferritic materials with high creep strength but poor oxidation resistance was investigated in order to allow increase in the operating temperature of steam power plants from 550 to 650 °C. Among the explored coating techniques for this application, chosen on the basis of being potentially appropriate for coating steam turbine components, High Velocity Oxy Fuel (HVOF) thermal spray has resulted in one of the most successful techniques. Different alloyed materials such as FeCrAl, NiCrSiFeB, FeAl, NiCr and FeCr have been deposited, optimized and tested under flowing steam at 650 °C. Characterization of as deposited and tested samples by metallography, SEM-EDS and XRD was carried out. Some of these coatings form protective pure chromium or aluminium oxides exhibiting excellent behaviour for at least 15 000 h of exposure, whereas others form less stable complex mixed oxides which nevertheless grow at considerably slower rates than the oxides formed on uncoated P92 (9 wt% Cr ferritic steel).
Acceso Abierto
Laboratory intercomparison of solar absorptance and thermal emittance measurements at room temperature
(Elsevier, 2022-05-14) Caron, Simon; Herding, L.; Binyamin, Yaniv; Baidossi, M.; Vinetsky, Y.; Morales, Angel; Hildebrandt, C.; Reoyo Prats, R.; Faugeroux, O.; Agüero, Alina; Rodríguez, Sergio; Sutter, Florian; Röger, M.; Manzano Agugliaro, F.; European Commission (EC)
Solar thermal absorber coatings play an important role in the opto-thermal efficiency of receivers in Concentrated Solar Power (CSP). Two standard figures of merit are the solar absorptance αsol and thermal emittance εth, derived from spectral directional hemispherical reflectance measurements at room temperature. These two figures of merit allow comparing coating formulations in terms of performance and durability. In this study, a black coating and a solar selective coating are optically characterized by different laboratories to compare spectral datasets, solar absorptance αsol and thermal emittance εth calculations. The comparison includes various benchtop spectrophotometers operating in the UV-VIS-NIR and Infrared spectral ranges as well as three commercial portable reflectometers/emissometers. A good agreement is found between the nine parties participating in this intercomparison campaign. The black coating αsol value is 96.6 ± 0.2%, while the solar selective coating αsol value is 94.5 ± 0.4%. For the thermal emittance, spectral data is concatenated and integrated from 0.3 to 16 μm. The black coating εth value calculated at 650 °C is 80.8 ± 3.8%, while the solar selective coating εth value calculated at 650 °C is 25.0 ± 0.5%.
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Long exposure steam oxidation testing and mechanical properties of slurry aluminide coatings for steam turbine components
(Elsevier, 2005-11-21) Osgerby, Steve; Pastor Muro, Ana; Agüero, Alina; Muelas Gamo, Raúl
Important efforts to develop new steels or to protect high creep strength steels in order to allow operation of steam turbines at 650 °C are being carried out world-wide to increase efficiency. Within the European Project “SUPERCOAT” (Coatings for Supercritical Steam Cycles), work has been concentrated in the development of coatings to withstand 50,000–100,000 h of operation at 650 °C under high pressure steam. Aluminide coatings on ferritic–martensitic steels produced by applying an Al slurry followed by a diffusion heat treatment, have shown to be protective at 650 °C under steam for at least 32,000 h of laboratory steam exposure under atmospheric pressure. Although the “as diffused” coatings present through thickness cracks, these do not propagate during exposure to steam or thermal cycling and no new cracks seem to develop. Moreover, no changes in residual stresses could be observed after thermal cycling. Microstructural characterization of samples at different periods of exposures has been carried out by SEM-EDS and XRD. The principal mechanism of coating degradation is loss of Al at the surface due to inwards diffusion. Microhardness as well as Young's modulus and fracture strength were measured using well established techniques. The coatings show reasonable ductility (∼1.6%) when stressed in tension between room temperature and 400 °C which further increases at higher temperatures providing evidence that the coatings should withstand the mechanical conditions likely to be encountered in service.
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Long term diffusion studies in Fe aluminide coatings deposited by slurry application on ferritic steel
(Scientific.Net, 2009-04-22) Agüero, Alina; González, Vanessa; Gutiérrez del Olmo, Marcos
Diffusion iron aluminide coatings have shown excellent resistance to high temperature oxidation in air, corrosive atmospheres and steam. A study of the diffusion behaviour of slurry applied diffusion aluminide coatings deposited on ferritic steel have been carried out under a 100% flowing steam atmosphere for up to 50,000 h at 650 °C. The results have shown that initially, the coating forms by outward growth possibly including the dissolution of the steel in molten aluminium. At later stages, during exposure to steam at 650 °C, aluminium diffuses inward and moreover, Fe also diffuses outward resulting in the progressive development of Kirkendall porosity. Results have also indicated that in order to form a pure protective Al2O3 scale the Al wt.% has to be > 4. Below this content Al-Fe mixed oxides develop exhibiting a less protective behaviour.
Restringido
Metal Dusting Protective Coatings. A Literature Review
(Springer Nature Link, 2011-03-20) Agüero, Alina; Gutiérrez del Olmo, Marcos; Korcakova, L; Nguyen, T. T. M; Hinnemann, B; Saadi, S
Metal dusting is a catastrophic form of carburization attack that takes place in carbon-supersaturated gaseous atmospheres, and is most commonly encountered in steam reforming processes such as the production of hydrogen or syngas for ammonia, Fischer–Tropsch and methanol applications. The consequence of metal dusting can be a severe loss of metal from the process units, leading to high-cost maintenance and serious safety issues. The present literature review discusses the latest developments within metal dusting protection of alloys with special emphasis on protective coatings. In the first part of the paper, an overview of the main theories for metal dusting of alloys as well as fundamental studies is provided. In the second part, the paper focuses on the different methods to prevent metal dusting, including surface poisoning, alloying, chemical, mechanical and laser treatments as well as coatings. Particular focus is given to coatings and their composition, and fabrication methods, and a critical analysis of the different materials’ behaviours and the suitability perspectives of deposition techniques are provided.
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Microstructural Evolution of Slurry Fe Aluminide Coatings during High Temperature Steam Oxidation
(Trans Tech Publications, 2008-09-15) Agüero, Alina; Spiradek, Krystina; Höfinger, S; Gutiérrez del Olmo, Marcos; Muelas Gamo, Raúl
Slurry iron aluminide coatings are very resistant to steam oxidation at 600-650º C. These coatings can be used to protect new generation Ultra Super Critical (USC) steam power plant ferritic/martensitic steel components. The microstructure of the initially deposited coating changes as a function of time, mainly due to coating-substrate interdiffusion, going from mostly Fe2Al5 to FeAl, causing the precipitation of AlN in those substrates containing a minimum content of N and moreover, developing Kirkendall porosity at the coating-substrate interface. Steam oxidation at 650º C causes the formation of a protective thin layer of hexagonal χ-Al2O3 phase along with some α- and γ-Al2O3 after the first few hours of exposure. However, despite the relatively low temperature, and after several thousands hours the protective layer was mostly composed of α-Al2O3. A study of the evolution of the microstructure of slurry aluminide coatings deposited on P92 and exposed to steam at 650º C has been carried out by scanning and transmission electron microscopy and X ray diffraction.
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Microstructures of thin and thick slurry aluminide coatings on Inconel 690
(Elsevier, 2007-07-05) Juul Rasmussen, Anders; Agüero, Alina; Gutiérrez del Olmo, Marcos; Landeira Østergård, María José
Two slurry aluminide coatings are produced on the Ni-base super alloy Inconel 690 by applying two different thicknesses of the same slurry on to the 690 substrate, followed by a two-step heat-treatment. The resulting thin aluminide coating consists of a single layer of Ni-rich β-NiAl matrix containing few large Cr precipitates with a high P content. The thick aluminide coating has a precipitate free inner layer of Ni-rich β-NiAl. An outer layer of Al-rich β-NiAl with many α-Cr precipitates has formed as well. The present metallurgical characterization shows a significant influence of slurry thickness on the morphology and composition of the coatings formed during heat treatment.
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Progress in the development of coatings for protection of new generation steam plant components
(Taylor and Francis online, 2008-11-15) Agüero, Alina
Coatings to prevent component oxidation in future supercritical high temperature steam turbines were developed for the first time in Europe during the COST522 programme. Promising results were obtained with slurry applied aluminide coatings and with a series of thermal sprayed coatings (FeAl, FeCrAl, NiCr and AlFeCoCr) deposited on P92. Since then, extensive research internationally has examined coatings to protect against steam oxidation, deposited by techniques including pack cementation, electroplating and chemical vapour deposition (fluidised bed and organometallic as well as thermal). The results of these studies, including steam oxidation and mechanical data are summarised, and the performance of the candidate systems is critically reviewed from the viewpoint of both materials behaviour and deposition technologies. An earlier version of this paper has been published in the proceedings of the "8th Advanced Power Generation" conference held in Liege, Belgium in September 2006. This version has been updated with the latest available results.
Acceso Abierto
Recubrimientos protectores para componentes de turbinas de aviación y de generación de energía depositados por proyección por plasma
(Elservier, 2000-07-26) Agüero, Alina; Álvarez Alba, J.; García de Blas, Javier; Valles González, M. P.
Coatings produced by aluminium diffusion, called aluminide are employed to increase the oxidation and corrosion resistance, increasing the life of Ni and Co base superalloys components at temperatures comprised between 900 and 1050ºC. Consequently these coatings are frequently employed in aeronautic and power generation turbines as well as in the chemical industry. Aluminides are industrially produced by pack cementation or CVD and recently it has been demonstrated that its resistance significantly increases when Cr is added (chrome-aluminides). During this work, a feasibility study has been carried out in order to determine if plasma spray can be employed for depositing this type of coatings on turbine blades. Therefore, aluminium and aluminium/chromium layers were deposited on Ni base IN100 superalloy specimens that were subsequently subjected to a diffusion heat treatment under Ar flow. Characterisation and analysis of the coatings were carried out by metallography , SEM and EDS. Cyclic oxidation tests were carried out at 1050º C while molten sulphate hot corrosion was performed at 900º C. The results of this preliminary study are promising and indicate that plasma spray can be developed as an industrial process for production of aluminide and chrome-aluminide coatings.

Los recubrimientos producidos por difusión de aluminio, llamados aluminuros, se emplean para aumentar la resistencia a la oxidación y a la corrosión, incrementando la vida de componentes fabricados con superaleaciones de níquel y cobalto a temperaturas comprendidas entre 900 y 1050º C. Por ello se emplean muy frecuentemente en turbinas aeronaúticas y de producción de energía y en la industria química. Los aluminuros se obtienen industrialmente mediante cementación o CVD y recientemente se ha demostrado que su resistencia aumenta significativamente cuando se añade cromo (cromoaluminuros). Durante el presente trabajo, se ha realizado un estudio de viabilidad para determinar si la proyección por plasma puede ser utilizada para la producción de estos recubrimientos sobre álabes de turbina. Así pues, se depositaron capas de aluminio y aluminio/cromo sobre probetas de la superaleción base níquel IN100 que a continuación fueron sometidas a un tratamiento térmico de difusión bajo flujo de argón. La caracterización y análisis de los recubrimientos producidos se llevó a cabo mediante técnicas metalográficas, microscopía electrónica de barrido y espectroscopía de dispersión de energía de rayos X. Se realizaron ensayos de oxidación cíclica a 1050ºC y de corrosión por sulfatos fundidos a 900ºC. Los resultados de este estudio preliminar han sido muy satisfactorios e indican que la proyección por plasma puede ser desarrollada como procedimiento industrial para la producción de recubrimientos aluminuros y cromoaluminuros.
Acceso Abierto
Slurry and Thermal Spray Coatings for Protection of New Generation Steam Engine Components
(ASM International, 2001-03-14) Agüero, Alina; Muelas Gamo, Raúl; Román Gárate, Alicia
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Steam Oxidation of Slurry Aluminide Coatings on Ferritic Steels for Advanced Coal-Fired Steam Power Plants
(Scientific.Net, 2004-08-12) Agüero, Alina; Muelas Gamo, Raúl
The use of slurry aluminide coatings on ferrite steels for advanced coal-fired steam power plants were analyzed. The materials used were found to have good high temperature oxidation resistance and deposited by techniques that can be employed to coat large steam turbine components either at the plant or at their location of manufacture. Laboratory steam oxidation testing as well as characterization of the coatings both before and after exposure was also presented. The results have provided information regarding the mechanism of protection and degradation of these coatings as well as insight for new coating development.
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Steam Oxidation Resistant Coatings for Steam Turbine Components: A Feasibility Study
(Scientific.Net, 2001-10-20) Agüero, Alina; García de Blas, Javier; Muelas Gamo, Raúl; Sánchez, A.; Tsipas, Sophia A.
The principal objective of the COST Action 522 is to raise the operating temperatures of both gas and steam turbines in order to increase their efficiency to reduce fuel consumption and emissions. Concerning steam turbines, the operating temperature is expected to rise from 550°C to 650°C, and the use of oxidation resistant coatings is being considered for the first time in Europe. In this preliminary work, two deposition techniques have so far been explored: slurry paints and atmospheric plasma spray (APS). Commercially available materials, known to have good oxidation resistance, were selected for both deposition techniques: one aluminium slurry and three alloyed materials for thermal spray: AlFe, FeCrAl and NiAl. The coatings were characterised by SEM-EDS and steam oxidation testing was carried out at 650°C. The preliminary findings show that some of the studied coatings may offer adequate protection.

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Examinando (Aeronáutica) Artículos por Autor "Agüero, Alina"