| 1. |
- Canovic, Sead, 1979, et al.
(author)
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Microstructural Investigation of the Initial Oxidation of the FeCrAlRE Alloy Kanthal AF in Dry and Wet O-2 at 600 and 800 degrees C
- 2010
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In: Journal of the Electrochemical Society. - : The Electrochemical Society. - 1945-7111 .- 0013-4651. ; 157:6, s. C223-C230
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Journal article (peer-reviewed)abstract
- The FeCrAlRE (where RE is reactive element) alloy Kanthal AF was exposed isothermally at 600 and 800 degrees C for 72 h in dry O-2 and in O-2 with 10 vol % H2O. The mass gains were 3-5 times higher at the higher temperature. The presence of water vapor increased the oxidation rate at 800 degrees C, while no significant effect was observed at 600 degrees C. A thin two-layered oxide formed at 600 degrees C: an outer (Fe, Cr)(2)O-3 corundum-type oxide, containing some Al, and an inner, probably amorphous, Al-rich oxide. At 800 degrees C a two-layered oxide formed in both environments. The inner layer consisted of inward grown alpha-Al2O3. In dry O-2 the originally formed outward grown gamma-Al2O3 had transformed to alpha-Al2O3 after 72 h. Water vapor stabilized the outward grown gamma-Al2O3 and hence no transformation occurred after 72 h in humid environment. RE-rich oxide particles with varying composition (Y, Zr, and Ti) were distributed in the base oxide at both temperatures and in both environments. The RE-rich particles were separated from the alloy substrate by a layer of Al-rich oxide. At 800 degrees C the Y-rich RE particles were surrounded by thick oxide patches in both dry and humid O-2.
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| 2. |
- Hall, Josefin, 1972, et al.
(author)
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The Initial Oxide Scale Development on a Model FeNiCrAl Alloy at 900 degrees C in Dry and Humid Atmosphere: A Detailed Investigation
- 2014
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In: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 82:3-4, s. 225-247
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Journal article (peer-reviewed)abstract
- The investigated alumina forming FeNiCrAl model alloy shows protective oxidation behavior in dry and humid environment at 900 A degrees C. Hence, this type of alloy may replace conventional chromia forming austenitic alloys in aggressive oxidizing/reducing environments. A detailed investigation of the oxide scale development reveals a complex initial scale development. Firstly, at alloy grain boundaries, a thin Al rich oxide forms which is replaced by transient alumina platelets in dry and equiaxed alpha-Al2O3 crystallites in humid atmosphere. The scale at alloy grain centers develops via a layered scale of external chromia:Fe/Ni metal inclusions:internal alumina to a layered external spinel:internal alumina scale in dry atmosphere. In humid condition an additional oxide feature appears on the center of large alloy grains i.e. thick oxide protrusions. Despite the initially different phase compositions a continuous protective alpha-Al2O3 scale forms both atmospheres.
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| 3. |
- Engkvist, Josefin, 1972, et al.
(author)
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Alumina scale formation on a powder metallurgical FeCrAl alloy (Kanthal APMT) at 900-1100°C in dry O2 and in O2 + H2O
- 2010
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In: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 73:1, s. 233-253
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Journal article (peer-reviewed)abstract
- A Rapidly Solidified Powder (RSP) metallurgical FeCrAl alloy, Kanthal APMT, was exposed in dry and humid O-2 for 72 h at 900-1,100 A degrees C. The formed oxide scales were characterized using gravimetry in combination with advanced analysis techniques (SEM, EDX, TEM, XRD, AES and SIMS). The oxide scales were at all exposures composed of two-layered alpha-Al2O3 scales exhibiting a top layer of equiaxed grains and a bottom layer containing elongated grains. A Cr-rich zone, originating in the native oxide present before exposure, separated these two layers. The top alpha-Al2O3 layer is suggested to have formed by transformation of outwardly grown metastable alumina, while the inward-grown bottom alpha-Al2O3 layer had incorporated small Zr-, Hf- and Ti-rich oxide particles present in the alloy matrix. The scale also contained larger Y-rich oxide particles. Furthermore, in the temperature range studied, the presence of water vapour accelerated alloy oxidation somewhat and affected scale morphology.
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| 4. |
- Hellström, Kristina M, 1971, et al.
(author)
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Mitigation of Fireside Corrosion in Power Plants: The Combined Effect of Sulfur Dioxide and Potassium Chloride on the Corrosion of a FeCrAl Alloy
- 2014
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In: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 28:9, s. 6116-6129
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Journal article (peer-reviewed)abstract
- The corrosion behavior of a FeCrAl alloy (Kanthal APMT) was investigated in 5% O-2 with 40% H2O plus 300 ppm of SO2 at 600 degrees C in the presence or absence of KCl, and the results were also compared to exposures performed without SO2 and KCl. The influence of preoxidation was also examined. The kinetics was followed using mass gain measurements, and the formed corrosion products were examined using XRD, SEM/EDX, AES, IC, and SIMS. The oxidation rate of Kanthal APMT was very low in O-2/N-2/H2O + 300 ppm of SO2, and the outward alumina growth appeared to be suppressed. Interestingly, no sulfur was detected at the scale/metal interface. KCl strongly accelerated the corrosion of Kanthal APMT in O-2/H2O/N-2 at 600 degrees C, forming K2CrO4 and gaseous HCl. Chromate formation depletes the protective scale in Cr, triggering the formation of a fast growing iron-rich scale. Adding SO2 suppressed the corrosion due to the conversion of the corrosive KCl to the stable K2SO4. If any K2CrO4 was formed on the surface of the material initially, it was also rapidly converted to K2SO4. Preoxidation of Kanthal APMT had a strong beneficial effect on the subsequent exposure at 600 degrees C in the presence of KCl and SO2, resulting in the formation of K2SO4 and the evaporation of HCl and KCl. In summary, the alumina-forming FeCrAl material Kanthal APMT is not completely inert to KCl in an oxidizing SO2-containing atmosphere at 600 degrees C. However, the corrosion rate is significantly lower than that of the commonly used chromia-forming alloy, 304L. Preoxidation decreases the corrosion rate even further, making Kanthal APMT a promising candidate material for combustion plant components, particularly from a corrosion point of view.
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| 5. |
- Hellström, Kristina M, 1971, et al.
(author)
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Oxidation behaviors and microstructural alterations of a Mo(Si,Al)(2)-based composite after heating at 1580 degrees C either in a furnace (ex-situ) or via alternating current (in-situ)
- 2015
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In: Journal of the European Ceramic Society. - : Elsevier BV. - 1873-619X .- 0955-2219. ; 35:2, s. 513-523
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Journal article (peer-reviewed)abstract
- The commercial heating element Kanthal Super ER (Mo(Si,Al)(2)-based composite) was oxidized at 1580 degrees C for 24 h up to 1 year using two methods: (1) a furnace set at the desired temperature, (2) passing an alternating current (AC) through the material. Initially, the oxidation behaviors appeared similar for the AC- and furnace-exposed materials. However, at longer exposure times, the level of Al depletion was more pronounced in the furnace-exposed material. A dense alumina scale formed with the same thickness during the two types of exposures, although a porous outer alumina scale was also formed on the composite that was heated in the furnace. The bulk microstructures were also different, in that dark regions in a circle were noted on the AC-exposed material, while the dark regions were evenly distributed on the furnace-exposed material. These dark regions consisted of agglomerated Mo-5(Si,Al)(3) and Al2O3. The AC-exposed material also has "bands" where Al2O3 have agglomerated.
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| 6. |
- Hellström, Kristina M, 1971, et al.
(author)
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Oxidation behaviour of a (Mo, W)Si2-based composite in dry and wet oxygen atmospheres in the temperature range 350–950◦C
- 2009
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In: Journal of the European Ceramic Society. - : Elsevier BV. - 1873-619X .- 0955-2219. ; 29:10, s. 2105-2118
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Journal article (peer-reviewed)abstract
- The oxidation of a (Mo, W)Si2-based composite was investigated in the temperature range (350–950 °C). The influence of temperature and water vapour on the oxidation was examined. The kinetics was studied using a thermobalance whereas the morphology and composition of the oxides were examined using X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive X-ray (EDX). Focused ion beam (FIB) milling was performed on some of the oxide scales which allowed us to look at a non-mechanically disturbed scale/oxide in cross-section. Rapid oxidation was found to occur in the 550–750 °C temperature range. The mass gains were significantly larger in O2 than in O2 + 10%H2O. The different mass changes in the two exposure atmospheres were attributed to the higher vapour pressure of the volatile MoO2(OH)2 and WO2(OH)2 species in O2 + 10%H2O than that of (MoO3)3 and (WO3)3 in dry O2. The peak mass gain was found to occur at a temperature of about 750 °C in O2 and 650 °C in O2 + 10%H2O. At temperatures above 850 °C, especially when water vapour is present, the removal of Mo and W from the oxide scales is rapid enough to allow partial healing of the silica, causing the oxidation rate to drop. At 950 °C in O2 + 10%H2O, a protective SiO2 scale could be re-established quickly and maintained, causing the oxidation to essentially cease.
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| 7. |
- Hellström, Kristina M, 1971, et al.
(author)
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Oxidation of a Dispersion-Strengthened Powder Metallurgical FeCrAl Alloy in the Presence of O2 at 1,100°C: The Influence of Water Vapour
- 2015
-
In: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 83:5-6, s. 533-558
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Journal article (peer-reviewed)abstract
- The oxidation behaviour of the FeCrAl alloy Kanthal(A (R)) APMT in O-2 + N-2 and O-2 + N-2 + H2O environments at 1,100 A degrees C was investigated using thermogravimetry and detailed analyses of the scale morphology with SEM/EDX and STEM/EDX. Wrought FeCrAl alloy Kanthal(A (R)) AF was used as a reference. Exposure time was up to 168 h. Water vapour influenced the early oxide growth kinetics. This effect is explained in terms of water acting as an oxidant, simultaneously with O-2. During later stages of the exposures, H2O had no effect on the kinetics of oxidation.
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| 8. |
- Hellström, Kristina M, 1971, et al.
(author)
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The Oxide Scales Formed on a Dispersion-Strengthened Powder Metallurgical FeCrAl Alloy at 900 A degrees C in O-2 and in O-2 + H2O
- 2015
-
In: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 84:1-2, s. 1-19
-
Journal article (peer-reviewed)abstract
- Early oxide scale growth on an oxide dispersion strengthened rapidly solidified powder FeCrAl material, Kanthal(A (R)) APMT, was investigated at 900 A degrees C in an O-2 + N-2 and an O-2 + H2O + N-2 environment for up to 168 h. Gravimetry was used to follow oxide growth and the oxide scale was examined with XRD. Scale morphology was investigated in detail with SEM/EDX, TEM/EDX/CBED. The alloy rapidly formed a protective two-layered alpha-alumina scale containing oxide nodules. Between the top and bottom alumina layers there was a zone containing chromia-rich particles 5-20 nm in diameter, corresponding to the original sample surface. The alumina scale mainly grew inward after 1 h of oxidation. Alumina scale growth at 900 A degrees C was initially somewhat faster in an O-2 + H2O + N-2 environment than in an O-2 + N-2 environment.
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| 9. |
- Ingemarsson, Linda, 1972, et al.
(author)
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Oxidation behavior at 300–1000C of a (Mo,W)Si2-based composite containing boride
- 2010
-
In: Intermetallics. - : Elsevier BV. - 0966-9795. ; 18:1, s. 77-86
-
Journal article (peer-reviewed)abstract
- The oxidation behavior of a (Mo,W)Si2 composite with boride addition was examined at 300–1000C for24 h in dry O2. The oxidation kinetics was studied using a thermobalance, and the oxide scales wereanalyzed using a combination of electron microscopy (SEM/EDX, FIB, BIB) and XRD. Accelerated oxidationwas found to occur between 500C and 675C, with a peak mass gain at 625C. The rapid oxidation isattributed to the vaporization of molybdenum oxide that leaves a porous and poorly protective silicalayer behind. At higher temperature (700–1000C) a protective scale forms, consisting of a dense SiO2/B2O3 glass.
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| 10. |
- Ingemarsson, Linda, 1972, et al.
(author)
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Oxidation behavior of a Mo (Si, Al)(2)-based composite at 300-1000 degrees C
- 2010
-
In: Intermetallics. - : Elsevier BV. - 0966-9795 .- 1879-0216. ; 18:4, s. 633-640
-
Journal article (peer-reviewed)abstract
- The oxidation behavior of a Mo (Si,Al)(2)-based composite of Mo(Si,Al)(2), Al2O3 and Mo-5(Si,Al)(3) (Kanthal Super ER) in synthetic air was investigated. The samples were oxidized isothermally for up to 72 h at 300-1000 degrees C using a thermobalance. The microstructure was analyzed by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Auger Electron Spectroscopy (AES) depth profiling. Broad ion beam milling (BIB) was used to prepare cross-sections. Oxidation behavior depended strongly on the composition of the substrate which consisted of a Mo(Si,Al)(2) matrix and the minority phases Mo-5(Si,Al)(3) and Al2O3. At 300-500 degrees C the mass gains were small with parabolic kinetics, oxidation resulting in a mixture of oxides that reflects the substrate composition. At 600 and 700 degrees C the oxide scale is thin and protective and depleted in molybdenum, a mass loss occurring due to MoO3 vaporization. At 1000 degrees C a protective alpha-alumina scale forms.
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| 11. |
- Ingemarsson, Linda, 1972, et al.
(author)
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Oxidation behavior of a Mo(Si,Al)2 composite at 900–1600 C in dry air
- 2013
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In: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 48:4, s. 1511-1523
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Journal article (peer-reviewed)abstract
- The oxidation of a Mo(Si,Al)2-based compositeis investigated in the temperature range 900–1600 C indry air. Exposure time was 72 h. Comparisons are madewith the oxidation behavior of a conventional MoSi2-basedmaterial. Cross-sections are examined with scanning electronmicroscopy and transmission electron microscopy; thephase composition is analyzed by X-ray diffraction andconvergent beam electron diffraction. The material forms acontinuous external a-alumina scale throughout the temperature range. Below the scale, there is a continuousMo5(Si,Al)3 layer that overlies Mo(Si,Al)2 in the bulk. TheMo(Si,Al)2 phase immediately beneath the Mo5(Si,Al)3layer is depleted in Al. No indications of MoO3 volatilization could be found for the Mo(Si,Al)2 material
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| 12. |
- Ingemarsson, Linda, 1972, et al.
(author)
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Oxidation behaviour of a Mo(Si,Al)2 based composite at 1500 degrees C
- 2011
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In: Intermetallics. - : Elsevier BV. - 0966-9795. ; 19:9, s. 1319-1329
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Journal article (peer-reviewed)abstract
- The oxidation of a Mo(Si,Al)(2) composite is investigated at 1500 degrees C in dry air using exposure times from 1 to 1000 h. Cross sections are examined with Scanning Electron Microscopy (SEM) and the phase composition is analyzed by X-ray diffraction (XRD). The material forms a continuous and protective alumina layer, the growth of the alumina layer following parabolic kinetics. Immediately below the scale Mo(Si,Al)(2) is replaced by a Mo(5)(Si,Al)(3) layer due to the flux of aluminum to the scale. The Al concentration in the Mo(Si,Al)(2) phase in the underlying substrate decreases from 27% before exposure to 16-17% after 1000 h. The continuous alumina layer becomes covered by a top layer consisting of alumina grains embedded in a viscous melt with approximate composition 7 Na(2)O-15 Al(2)O(3)-78 SiO(2). With time, sodium is volatilized from the melt and the top scale layer transforms to a mixture of alumina, mullite and silica melt.
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| 13. |
- Israelsson, Niklas, 1983, et al.
(author)
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A Microstructural and Kinetic Investigation of the KCl-Induced Corrosion of an FeCrAl Alloy at 600 A degrees C
- 2015
-
In: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 84:1-2, s. 105-127
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Journal article (peer-reviewed)abstract
- The corrosion behaviour of a FeCrAl alloy was investigated at 600 A degrees C in O-2 + H2O with solid KCl applied. A kinetics and microstructural investigation showed that KCl accelerates corrosion and that potassium chromate formation depletes the protective scale in Cr, thus triggering the formation of a fast-growing iron-rich scale. Iron oxide was found to grow both inward and outward, on either side of the initial oxide. A chromia layer is formed with time underneath the iron oxide. It was found that although the alloy does not form a continuous pure alumina scale at the investigated temperature, aluminium is, however, always enriched at the oxide/alloy interface.
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| 14. |
- Israelsson, Niklas, 1983, et al.
(author)
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Cyclic Corrosion and Chlorination of an FeCrAl Alloy in the Presence of KCl
- 2015
-
In: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 84:3-4, s. 269-290
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Journal article (peer-reviewed)abstract
- The KCl-induced corrosion of the FeCrAl alloy Kanthal® APMT in an O 2 + N 2 + H 2 O environment was studied at 600 °C. The samples were pre-oxidized prior to exposure in order to investigate the protective nature of alumina scales in the present environment. The microstructure and composition of the corroded surface was investigated in detail. Corrosion started at flaws in the pre-formed α-alumina scales, i.e. α-alumina was protective in itself. Consequently, KCl-induced corrosion started locally and, subsequently, spread laterally. An electrochemical mechanism is proposed here by which a transition metal chloride forms in the alloy and K 2 CrO 4 forms at the scale/gas interface. Scale de-cohesion is attributed to the formation of a sub-scale transition metal chloride.
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| 15. |
- Israelsson, Niklas, 1983, et al.
(author)
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KCl-Induced Corrosion of an FeCrAl Alloy at 600°C in O2 + H2O Environment: The Effect of Pre-oxidation
- 2015
-
In: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 83:1-2, s. 29-53
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Journal article (peer-reviewed)abstract
- The present study investigates the influence of H2O and KCl on the high temperature corrosion of an FeCrAl alloy at 600 A degrees C. Polished samples were exposed to O-2 or O-2 + H2O and to O-2 + H2O with KCl applied. The samples were investigated using SEM/EDX, XRD, IC, AES and SIMS. It was found that KCl accelerates corrosion and that a rapidly growing iron-rich oxide forms with time. Chromate formation is shown to initiate the formation of a non-protective oxide scale. Pre-oxidising the alloy before exposure in the presence of KCl had a strongly beneficial effect on the corrosion.
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| 16. |
- Israelsson, Niklas, 1983, et al.
(author)
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KCl-Induced Corrosion of the FeCrAl Alloy Kanthal® AF at 600°C and the Effect of H2O
- 2015
-
In: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 83:1-2, s. 1-27
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Journal article (peer-reviewed)abstract
- The present study investigates the influence of H2O and KCl on the high-temperature corrosion of the FeCrAl alloy Kanthal(A (R)) AF. Polished samples, with and without applied KCl, were exposed isothermally to O-2 or O-2 + H2O at 600 A degrees C. The samples were investigated using TGA, XRD, SEM/EDX, AES and IC. It was found that KCl accelerates corrosion and that a rapidly growing iron, chromium-rich oxide forms in both environments. Chromate formation and alloy chlorination are shown to initiate the formation of non-protective oxide scales. In addition, aluminium nitrides form in the alloy substrate in both environments.
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| 17. |
- Larsson, Erik, 1983, et al.
(author)
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A Comparative Study of the Initial Corrosion of KCl and PbCl2 on a Low-Alloyed Steel
- 2017
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In: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 87:5-6, s. 779-787
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Journal article (peer-reviewed)abstract
- Heat exchange surfaces in biomass- and waste-fired boilers are exposed to corrosive species due to the considerable amounts of alkali chlorides and PbCl2 which are released during combustion. The corrosivity of alkali chlorides toward superheater alloys exposed at high temperature has been studied extensively. However, at lower material temperatures, i.e., at waterwall conditions, considerably less research has been performed. In order to investigate the effect of small amounts of KCl and PbCl2 during the initial stages of the corrosion attack, a Fe–2.25Cr–1Mo steel was exposed for 24 h in an atmospheres consisting of O2 + H2O + N2 at 400 °C. Both KCl and PbCl2 resulted in an increased corrosion rate compared to the reference. The aim of the present paper is to investigate the influence of KCl and PbCl2 on the initial oxidation of a Fe–2.25Cr–1Mo steel. The work involves a detailed microstructural investigation as well as thermodynamic equilibrium calculations.
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| 18. |
- Liu, Fang, 1975, et al.
(author)
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First Three-Dimensional Atomic Resolution Investigation of Thermally Grown Oxide on a FeCrAl Alloy
- 2015
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In: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 83:5-6, s. 441-451
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Journal article (peer-reviewed)abstract
- Thermally grown Al2O3 scales formed on a FeCrAl alloy, Kanthal APMT, were successfully analysed using pulsed green laser atom probe tomography. The alloy was exposed to 5 vol.% O-2 + 95 vol.% N-2 at 900 A degrees C for 1 h, and covered by a thin layer of Al2O3. Cr segregation to some of the Al2O3 grain boundaries was observed. The continuous Cr-rich band, which contains a large number of Cr- and/or Fe- enriched nano-sized particles, was studied in detail. Four types of nanoparticles were found and analysed. Oxidation mechanisms at the initial stages are discussed based on the observations.
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| 19. |
- Malmberg, Per, 1974, et al.
(author)
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The elemental distribution in the oxide scale on a conventionally cast and a metallurgical ODS FeCrAl alloy characterized by ToF-SIMS
- 2014
-
In: Surface and Interface Analysis. - : Wiley. - 1096-9918 .- 0142-2421. ; 46:S1, s. 281-284
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Journal article (peer-reviewed)abstract
- The commercial FeCrAl alloys Kanthal APMT(TM) (powder metallurgical) and Kanthal AF(TM) (conventionally cast) contain reactive elements (RE) to improve scale properties. These alloys were oxidized at 1100 degrees C for 168h to form a protective alumina scale. These scales were then investigated with Time of flight secondary ion mass spectrometry to examine the distribution of the REs. The results showed an accumulation of Y, Zr, Mg and Mo in the outermost part of the oxide scales on both alloys. Low levels of these elements were also detected in the oxide scales. In addition, Mo was accumulated together with Cr in the oxide of APMT.
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