(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, Pauline; Sergio, Rodríguez Catela; 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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A simple lab screening test to evaluate ice adhesion
(Elsevier, 2025-09) García, Paloma; Mora, Julio; Agüero, Alina; Ministerio de Economía y Competitividad (MINECO)
Ice formation is a major problem for many sectors such as aeronautics, power generation, maritime, communications, etc. and therefore, there is a growing demand for anti-icing surface modification technologies. Being able to compare and evaluate these materials at the laboratory scale is a challenge for which a unified response has not yet been given. There are no standards for evaluating icephobicity despite the fact that there are numerous studies focused on the influence of the surface topography on the wetting behavior. In addition, several testing options have been published both for the evaluation of ice accretion, mainly focused on ice wind tunnels (IWT), and on ice to substrate adhesion, as for instance the zero degree cone test, DLST, Cantilever, centrifugal tests, etc. This article describes a method developed to carry out a simple screening evaluation of ice adhesion by the double lap shear test (DLST) method. This technique can provide qualitative ice adhesion information and is commonly available in research laboratories. Moreover, it does not require icing wing tunnel testing. Its ease of execution and reproducibility makes it a useful tool for a first stage evaluation of anti-icing surfaces despite the fact that ice is formed under static conditions. Various materials and surface finished surfaces with different degree of ice adhesion strength were evaluated and were also tested in a centrifugal adhesion test with ice accreted in an IWT. The results showed that the DLST is valid for ice adhesion classification of materials, but shows limitations for those superhydrophobic materials that are in the Cassie-Baxter state.
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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.
Acceso Abierto
Aluminide Coatings by Means of Slurry Application: A Low Cost, Versatile and Simple Technology
(MPDI, 2024-09-29) Agüero, Alina; Audigié, Pauline; Lorente Sánchez, Cristina; Gutiérrez del Olmo, Marcos; Mora, Julio; Sergio, Rodríguez Catela; European Commission; Agencia Estatal de Investigación (España)
The present study focused on demonstrating the versatility of the slurry deposition technique to produce aluminide coatings to protect components from high-temperature corrosion in a broad temperature range, from 400 to 1400 °C. This is a simpler and low-cost coating technology used as an alternative to CVD and pack cementation, which also allows the coating of complex geometries and offers improved and simple repairability for a lot of industrial applications, along with avoiding the use of non-hazardous components. Slurry aluminide coatings from a proprietary water-based-Cr6+ free slurry were produced onto four different substrates: A516 carbon steel, 310H AC austenitic steel, Ti6246 Ti-based alloy and TZM, a Mo-based alloy. The resulting coatings were thoroughly characterised by FESEM and XRD, mainly so that the identification of microstructures and appropriate phases was reported for each coating. The importance of surface preparation and heat treatment as key parameters for the coating final microstructures was also evidenced, and how those parameters can be optimised to obtain stable intermetallic phases rich in Al to sustain the formation of a protective Al2O3 oxide scale. These coating systems have applications in diverse industrial environments in which high-temperature corrosion limits the lifetime of the components.
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Aluminum slurry coatings to replace cadmium for aeronautic applications
(Elsevier, 2012-10-27) Agüero, Alina; del Hoyo Gordillo, Juan Carlos; García de Blas, Javier; García, M.; Gutiérrez, M.; Madueño, L.; Ulargui, S.
Cadmium has been widely used as a coating to provide protection against galvanic corrosion for steels and for its natural lubricity on threaded applications. However, it is a toxic metal and a known carcinogenic agent, which is plated from an aqueous bath containing cyanide salts. For these reasons, the use of cadmium has been banned in Europe for most industrial applications. However, the aerospace industry is still exempt due to the stringent technical and safety requirements associated with aeronautical applications, as an acceptable replacement is yet to be found. Al slurry coatings have been developed as an alternative to replace cadmium coatings. The coatings were deposited on AISI 4340 steel and have been characterized by optical and electron microscopy. Testing included salt fog corrosion exposure, fluid corrosion exposure (immersion), humidity resistance, coating-substrate and paint-coating adhesion, electric conductivity, galvanic corrosion, embrittlement and fatigue. The results indicated that Al slurry coatings are an excellent alternative for Cd replacement.
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Anomalous steam oxidation behavior of a creep resistant martensitic 9 wt. % Cr steel
(Elsevier, 2013-06-09) Agüero, Alina; González, Vanessa; Mayr, Peter; Spiradek Hahn, Krystina; Ministerio de Economía y Competitividad (MINECO)
The efficiency of thermal power plants is currently limited by the long-term creep strength and the steam oxidation resistance of the commercially available ferritic/martensitic steel grades. Higher operating pressures and temperatures are essential to increase efficiency but impose important requirements on the materials, from both the mechanical and chemical stability perspective. It has been shown that in general, a Cr wt. % higher than 9 is required for acceptable oxidation rates at 650 °C, but on the other hand such high Cr content is detrimental to the creep strength. Surprisingly, preliminary studies of an experimental 9 wt. % Cr martensitic steel, exhibited very low oxidation rates under flowing steam at 650 °C for exposure times exceeding 20,000 h. A metallographic investigation at different time intervals has been carried out. Moreover, scanning transmission electron microscopy (STEM) analysis of a ground sample exposed to steam for 10,000 h at 650 °C revealed the formation of a complex tri-layered protective oxide comprising a top and bottom Fe and Cr rich spinel layer with a magnetite intermediate layer on top of a very fine grained zone.
Restringido
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
Comparison of descaling methods to study the corrosion kinetics of ferritic steels after dynamic exposure to molten carbonates
(Elsevier, 2022-12-24) Audigié, Pauline; Sergio, Rodríguez Catela; Agüero, Alina; Pedrosa, Fátima; Paiva, Teresa; Diamantino, Teresa C.
T91 ferritic-martensitic steel was exposed to Li, Na and K molten carbonates at 650ºC under dynamic conditions up to 1000 h. After testing, three descaling methods, two from the ISO8407 and one from the ISO17245 standards were applied to remove the corrosion products and determine the corrosion rates. The two ISO8407 methods were more appropriate although the procedure required several steps to fully remove the corrosion products. The ISO17245 method led to a higher mass loss affecting probably the base material. Oxides identification was performed by XRD following step by step layers removal. Li-, Na-, K-containing oxides and chromates/chromites were detected.
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Corrosion Resistance of Novel Coatings on Ferritic Steels for Oxycombustion–Supercritical Steam Boilers: Preliminary Results
(Springer Nature Link, 2015-07-23) Agüero, Alina; Baraibar, Ignacio; González, Vanessa; Muelas Gamo, Raúl; Plana, Daniel; European Commission; Ministerio de Economía y Competitividad (MINECO)
Increasing the efficiency of coal fired steam power plants is an important contribution towards clean coal power. In fact, new ferritic steels are expected to withstand 325 bar and 650 °C. Moreover, in order to facilitate CO2 capture oxygen can be used instead of air for combustion (oxycombustion) so that no NOX emissions are produced. Boiler components, such as superheater tubes, are exposed to both steam and fireside corrosion and at higher temperatures, ferritic steels corrode at very fast rates under both atmospheres. A solution can be found in the use of protective coatings, a number of which, applied by techniques capable of depositing said coatings both on the inner and outer surfaces of tubes, are being studied within nationally and European funded projects. In particular, two new Ni and Cr modified aluminide coatings deposited on P92 by non-line-of-sight hybrid processes have been produced and the preliminary results of on-going laboratory testing, both under oxycombustion model atmospheres as well as under pure steam at 650 °C are promising, in particular those exhibited by the Cr enriched aluminide coating. Moreover, results obtained in a pilot oxycombustion boiler operated by CIUDEN in Leon, Spain are also shown.
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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.
Restringido
Effects of a Steam Pre-treatment on the Formation and Transformation of Alumina Phases on Fe Aluminide Coatings
(Springer Nature Link, 2012-12-25) Agüero, Alina; Hernández, M.; Santaballa, A.; Ministerio de Economía y Competitividad (MINECO)
Several researchers have studied the transformation of metastable aluminas (γ- and θ-) to α-Al2O3 but very little is known regarding alumina scales formed under water vapour and their transformation to α-Al2O3. Some results have indicated that water vapour increases the oxidation rate of alumina-scale forming coatings but others have found the opposite, that is, that under water vapour the oxidation rates decrease as either transition aluminas do not form or the transformation to α-Al2O3 is accelerated. In addition, it was found that χ-Al2O3 is the only oxide that forms at the initial stages of oxidation under 100 % steam on Fe–Al coatings at 650 °C. Under these conditions, this oxide is very protective, and slowly transforms onto α-Al2O3. A preliminary study of the transformation of χ- to α-Al2O3 at 900 °C under laboratory air was carried out. χ-Al2O3 was generated by a steam pre-treatment on slurry Fe aluminide coatings deposited on P92.
Acceso Abierto
Estudio del Tratamiento Térmico de Difusión de Recubrimientos de Al sobre aceros ferrítico
(Arrola, 2014-01-04) Agüero, Alina; Gutiérrez del Olmo, Marcos; González, Vanessa
Restringido
High temperature corrosion beneath carbonate melts of aluminide coatings for CSP application
(Elsevier, 2020-03-20) Audigié, Pauline; Encinas Sánchez, V.; Sergio, Rodríguez Catela; Pérez Trujillo, Francisco Javier; Agüero, Alina; European Commission
Slurry iron-aluminide coatings deposited by spraying on 9 wt% Cr P91 alloy as well as uncoated P91 were exposed isothermally at 650 °C to a ternary molten salt mixture based on a Na, K and Li carbonate eutectic, under static and dynamic conditions. Uncoated P91 evidenced considerable mass gains and extensive spallation in both conditions. Indeed, P91 developed a very thick fast growing multilayered oxide scale which included LiFeO2, LiFe5O8 and (Fe,Cr)3O4. Under dynamic conditions, the metal loss was higher that when the test was carried out statically but this was not reflected in the gravimetric measurements likely due to spallation of the scales in both cases. The coated systems performed better than the uncoated material up to at least 1000 h according to metallographic inspection. However, the aluminide coating showed non-uniform attack and on the corresponding zones, a thick layer likely consisting of LiFeO2 developed over an internal oxidation zone corresponding to all of the coating initial thickness. K was also detected within the internal oxidation zone suggesting that the coating was internally attacked at least by K containing species (Li cannot be detected by EDS). K and perhaps Li seem to diffuse along the grain boundaries of the coating, leading to internal oxidation responsible for the degradation. On the non-degraded zones, the coating maintained the initial microstructure as very low coating/substrate interdiffusion occurred. A 20 wt% average Al content at the surface does not seem to be high enough to sustain a protective oxide.
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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.
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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).
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HVOF-Deposited WCCoCr as Replacement for Hard Cr in Landing Gear Actuators
(Springer Nature Link, 2011-10-05) Agüero, Alina; Camón, F.; García de Blas, Javier; del Hoyo Gordillo, Juan Carlos; Muelas Gamo, Raúl; Santaballa, A.; Ulargui, S.; Vallés, P.
WCCoCr coatings deposited by HVOF can replace hard Cr on landing gear components. Powders with two different WC particle sizes (micro and nano-) and geometries have been employed to study the effects on the coating’s properties. Moreover, coatings produced employing two sets of parameters resulting in high and low flame temperatures have been evaluated. Minor differences in microstructure and morphology were observed for the two powders employing the same spraying parameters, but the nano-sized powder exhibited a higher spraying efficiency. However, more significant microstructural changes result when the low- and high-energy spray parameters are used. Moreover, results of various tests which include adhesion, wear, salt fog corrosion resistance, liquid immersion, and axial fatigue strength, indicate that the coatings produced with high-energy flame are similar in behavior. On the other hand, the nanostructured low-energy flame coating exhibited a significantly lower salt fog corrosion resistance.
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Laboratory corrosion testing of coatings and substrates simulating coal combustion under a low NOx burner atmosphere
(Wiley online library, 2013-07-02) Agüero, Alina; Gutiérrez del Olmo, Marcos; Muelas Gamo, Raúl; Plana, Daniel; Román, A.; Hernández, M.
It is certainly a difficult task to evaluate new materials and coatings to be used for boilers in power plants, as conditions are extremely complex, comprising a highly erosive environment, high temperature, highly corrosive gases, and reactive deposits. In particular, early catastrophic failures, as well as higher degradation rates have been observed on different power plant boiler components when operating under atmospheres containing low levels of oxygen. These atmospheres are typical of low NOx burners, and can be more corrosive than normal oxidizing conditions. The presence of a sulfidizing atmosphere as well as ash deposits present in boilers, are in part responsible of this accelerated damage. In this work, testing under a low oxygen atmosphere has been carried out on T22 and P92 uncoated and coated specimens. The atmosphere was equal to that measured in a Spanish coal-fired power plant (ENDESA, Compostilla, León) and the test temperature was 580 °C. Tested coatings were slurry applied aluminides, as well as two HVOF sprayed coatings including a commercially deposited Cr2C3NiCr, and a newly developed Cr2O3-Cr composite coating. The specimens were covered with ash (taken from the plant) prior to testing. After testing, the uncoated substrates exhibited high thickness oxides with some sulfide inclusions whereas all tested coatings were very protective. Exposed samples of T22 tubes employed in the Compostilla power plants were analyzed and compared with the corresponding specimens tested in the laboratory. In both cases, the scales contained Fe3O4 and FeS but the sulfide content was significantly higher in the scale formed in the plant. Moreover, ash particles were found embedded in the both scales.

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