Proyecto de Investigación: BELENUS 815147
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815147
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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.
Rapid α-Al2O3 Growth on an Iron Aluminide Coating at 600 °C in the Presence of O2, H2O, and KCl
(ACS Publications, 2024-10-17) Agüero, Alina; Audigié, Pauline; Sergio, Rodríguez Catela; Gutiérrez del Olmo, Marcos; Pascual Ferreiro, Jon; Ssenteza, Vicent; Jonsson, Torbjörn; Johansson, Lars Gunnar; Agencia Estatal de Investigación (España); European Commission
In this work, a slurry iron aluminide-coated ferritic steel SVM12 was subjected to a laboratory experiment mimicking superheater corrosion in a biomass-fired power boiler. The samples were exposed under model Cl-rich biomass conditions, in a KCl + O2 + H2O environment at 600 °C for 168, 2000, and 8000 h. The morphology of corrosion and the composition of the oxide scale and the coating were investigated by a combination of advanced analytical techniques such as FESEM/EDS, SEM/EBSD, and XRD. Even after short-term exposure, the coating developed a very fast-growing and up to 50 μm thick α-Al2O3 scale in contrast to the spontaneous formation of a protective, thin, dense, slow-growing, and very adhesive α-Al2O3 layer usually formed on metallic materials after high-temperature oxidation. In view of the literature on the formation of oxide scales on alloys and coatings, the formation of an α-Al2O3 scale at this relatively low temperature is very surprising in itself. The thick alumina scale was not protective as its formation resulted in fast degradation of the coating and rapid Fe2Al5 → FeAl phase transformation, which in turn generated porosity inside the coating. In all cases, the resulting thick Al2O3 scale was porous and consisted of both equiaxed α-Al2O3 grains and randomly oriented aggregated alumina whiskers. Potassium is concentrated in the outer part of the Al2O3 scale, while chlorine is concentrated close to the scale/aluminide interface. The unexpected formation of rapidly growing α-Al2O3 at relatively low temperature is attributed to the hydrolysis of aluminum chloride generated in the corrosion process.
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.
Modified high hardness steel coating for biomass corrosion protection
(Springer Nature Link, 2025-09-13) Agüero, Alina; Gutiérrez del Olmo, Marcos; Audigié, Pauline; Sergio, Rodríguez Catela; Pascual Ferreiro, Jon
Biomass is a renewable and CO2-neutral energy source. However, the efficiency of biomass combustion plants remains lower than that of current fossil fuel-based systems. To minimize corrosion from aggressive species found in biomass combustion, these plants currently operate at a maximum temperature of 550 °C. The European project BELENUS explored new materials and coatings to raise the operating temperature to 600 °C, thereby improving plant efficiency. Among the coatings under investigation, a super high-hardness steel (SHS) modified with Al, applied by high velocity oxy-fuel (HVOF) thermal spray on ferritic steel SVM12, has demonstrated an improved performance in the laboratory, exposed to a model biomass environment containing KCl deposits for 8000 h at 600 °C. Microstructural analysis by field emission scanning electron microscopy (FESEM) and X-ray diffraction was conducted on the tested samples to examine the coating’s evolution in these environments, as well as the associated protection and degradation mechanisms. The presence of Al within the coating significantly enhanced its resistance to biomass corrosion when compared to uncoated SVM12 and the Al-free SHS coating. Possible reasons for the improved behaviour of the Al-modified coating are the reduction of porosity as well as the blocking effect of either intermetallic FeAl or Al oxide which forms at the splat boundaries prior to exposure to the corrosive atmosphere.
