| 1. |
- Ingemarsson, Linda, 1972, et al.
(författare)
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Oxidation behavior at 300–1000C of a (Mo,W)Si2-based composite containing boride
- 2010
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Ingår i: Intermetallics. - : Elsevier BV. - 0966-9795. ; 18:1, s. 77-86
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Jonsson, Torbjörn, 1970, et al.
(författare)
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Oxidation of Fe-10Cr in O-2 and in O-2+H2O environment at 600 degrees C: A microstructural investigation
- 2013
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X. ; 75, s. 326-336
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Tidskriftsartikel (refereegranskat)abstract
- Oxidation of Fe-10Cr in dry and wet O-2 was studied at 600 degrees C for up to 168 h. Oxide microstructure was investigated by STEM/EDX, FIB/SEM and TEM. Oxidation in dry O-2 gives a Cr-rich protective (Fe1-xCrx)(2)O-3 scale. The same protective oxide initially forms in O-2 + H2O environment, but after an incubation period scale breakdown is triggered by CrO2(OH)(2) evaporation that depletes the substrate in Cr and converts (Fe1-xCrx)(2)O-3 to FeCr spinel oxide. Internal oxidation occurs after breakaway. Alternating external and internal oxidation result in the inward-growing scale showing a characteristic banded morphology.
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| 3. |
- Pujilaksono, Bagas, 1965, et al.
(författare)
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Oxidation of Binary FeCr Alloys (Fe–2.25Cr, Fe–10Cr, Fe–18Cr and Fe–25Cr) in O2 and in O2 + H2O Environment at 600 °C
- 2011
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Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 75:3, s. 183-207
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Tidskriftsartikel (refereegranskat)abstract
- The oxidation behaviour of the binary alloys Fe-2.25Cr, Fe-10Cr, Fe-18Cr and Fe-25Cr (wt%) in dry and wet O 2 at 600 °C is investigated by isothermal exposures of carefully polished samples for up to 168 h. The oxidized samples are investigated gravimetrically and the oxides formed are studied by X-ray diffraction. X-ray photoelectron spectroscopy is used for depth profiling of the thin oxides. The scale surface is imaged by SEM. Cross-sections through the scale are analyzed by SEM/EDX for imaging and for measuring the chemical composition. The oxidation behavior of the four FeCr alloys is intermediate between those of iron and chromium. Fe-2.25Cr oxidizes in a way similar to iron in both environments, forming a poorly protective scale consisting of FeCr spinel at the bottom, magnetite in the middle and a hematite cap layer. In dry O 2, Fe-10Cr, Fe-18Cr and Fe-25Cr form a thin and protective (Fe,Cr) 2O 3 oxide similar to the chromia film formed on pure chromium. In wet O 2, Fe-10Cr, Fe-18Cr and Fe-25Cr initially form the same kind of protective oxide film as in dry conditions. After an incubation time that depends on alloy chromium content, all three alloys go into breakaway oxidation and form thick, poorly protective scales similar to those formed on Fe-2.25Cr. Breakaway oxidation in wet O 2 is triggered by the evaporation of CrO 2(OH) 2 from the protective (Fe,Cr) 2O 3 oxide.
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| 4. |
- Pujilaksono, Bagas, 1965, et al.
(författare)
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Oxidation of iron at 400-600 °C in dry and wet O2
- 2010
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X. ; 52:5, s. 1560-1569
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Tidskriftsartikel (refereegranskat)abstract
- The oxidation of iron in dry and wet O-2 at 400-600 degrees C has been re-investigated using gravimetry, SEM/EDX, XRD and FIB. In the presence of O-2, water vapour accelerates iron oxidation at 500 and 600 degrees C. At 400 and 500 degrees C the magnetite layer is duplex and exposure to water vapour results in the formation of blades on top of a fine-grained hematite layer. At 600 degrees C it results in a surface without needles and blades. The increased oxidation rate at 500 and 600 degrees C is attributed to a smaller grain size in the hematite layer resulting in faster ion transport.
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| 5. |
- Canovic, Sead, 1979, et al.
(författare)
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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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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 1945-7111 .- 0013-4651. ; 157:6, s. C223-C230
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Tidskriftsartikel (refereegranskat)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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| 6. |
- Canovic, Sead, 1979, et al.
(författare)
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Oxidation of Co- and Ce-nanocoated FeCr steels: A microstructural investigation
- 2013
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Ingår i: Surface and Coatings Technology. - : Elsevier BV. - 0257-8972. ; 215, s. 62-74
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Tidskriftsartikel (refereegranskat)abstract
- The effect of novel Co and Ce nanocoatings on oxidation behaviour and chromium volatilization from a commercial Fe-22Cr steel (Sanergy HT) developed for solid oxide fuel cell interconnect applications is investigated. Three different coatings (10 nm Ce, 640 nm Co and 10 nm Ce + 640 nm Co) are studied. Uncoated and nanocoated samples are exposed isothermally at 850 C in the air with 3% H2O for 168 h. The detailed microstructure of the different coatings is investigated. The surface morphology and microstructure of the oxide scales are characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and energy dispersive X-ray analysis (EDX). Cross-section TEM thin foils are prepared by using a combined FIB/SEM (focused ion beam/scanning electron microscope) instrument. A 640 nm cobalt coating strongly inhibits Cr volatilization but has only minor effects on oxidation rate. In contrast, a 10 nm Ce coating decreases the oxidation rate but has no significant effects on chromium volatilization. Combining the two coatings, i.e., applying a 640 nm Co coating on top of the 10 nm Ce, effectively reduces Cr evaporation and slows down the rate of alloy oxidation.
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| 7. |
- Engkvist, Josefin, 1972, et al.
(författare)
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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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Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 73:1, s. 233-253
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Tidskriftsartikel (refereegranskat)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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| 8. |
- Esmaily, Mohsen, 1987, et al.
(författare)
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Influence of temperature on the atmospheric corrosion of the MgAl alloy AM50 produced by semi-solid cast and high pressure die cast technique
- 2013
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Ingår i: Proceedings of the International Congress on Light Materials-Science and Technology (LightMAT 2013), Bremen, Germany, In: Characterisation, Simulation, In: Corrosion, Editor: A. Lohmüller.
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Konferensbidrag (refereegranskat)abstract
- The effect of temperature on the atmospheric corrosion of the MgAl alloy AM50 was investigated in the laboratory. The alloy was investigated in both semi-solid cast and high pressure die cast form. Polished samples were exposed to air containing 400ppm CO2 for up to 4 weeks at 22ºC, 4ºC and -4oC at 95% relative humidity (RH). The rate of corrosion was determined by mass gain and metal loss measurements. The corrosion products were analyzed by SEM/EDX. Analysis by XRD showed that the composition of the crystalline corrosion product depended on the exposure temperature. Both materials exhibited a strong positive correlation between temperature and the rate of NaCl-induced atmospheric corrosion. It is suggested that the temperature dependence of corrosion is related to the dissolution of alumina in the passive film. The semi-solid cast material exhibited lower average corrosion rates at all three temperatures.
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| 9. |
- Esmaily, Mohsen, 1987, et al.
(författare)
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Microstructural characterization of the Mg-Al alloy AM50 produced by a newly developed rheo-casting process
- 2014
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Ingår i: Materials Characterization. - : Elsevier BV. - 1044-5803 .- 1873-4189. ; 95, s. 50-64
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Tidskriftsartikel (refereegranskat)abstract
- The microstructure of rheo-cast Mg-Al alloy AM50 produced by the RheoMetal process is investigated and compared with the same alloy produced by conventional high pressure die casting. The size and arrangement of microstructural constituents and pores are characterized quantitatively using image analyzing techniques. The nearest neighbor distribution of the intermetallic particles is determined. The area fraction of porosity in rheo-cast AM50 is about half that found in the high pressure die cast alloy. In rheo-cast material, the distribution of p phase (Mg17Al12) is relatively uniform throughout the cast. In contrast, the beta phase particles tend to form macroscopic agglomerates in high pressure die cast material. The externally solidified grains in the rheo-cast material exhibit a smaller aluminum gradient than in the high pressure die cast alloy. This indicates that the solidification of the rheo-cast material is closer to equilibrium.
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| 10. |
- Folkeson, Nicklas, 1981, et al.
(författare)
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The influence of small amounts of KCl(s) on the high temperature corrosion of a Fe-2.25Cr-1Mo steel at 400 and 500 degrees C
- 2011
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Ingår i: Materials and Corrosion - Werkstoffe und Korrosion. - : Wiley. - 1521-4176 .- 0947-5117. ; 62:7, s. 606-615
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports the oxidation behaviour of a low-alloyed steel (Fe-2.25Cr-1Mo) in the presence of small amounts of KCl(s) at 400 and 500 degrees C. Cleaned and polished sample coupons were exposed in a horizontal tube furnace with exposure times ranging from one hour to one week. The flue gas composition was 5% O(2) with 40% H(2)O in N(2), and 0.1mg KCl/cm(2) was deposited on the samples prior to exposure. X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis were used to characterize the samples. Cross sections were prepared by means of focused ion beam (FIB) and broad ion beam (BIB). At 400 degrees C there was a modest mass gain in the absence of KCl. In the presence of KCl, mass gain is significantly increased and a rapid attack is evident already after short exposure times. At 500 degrees C, the mass gains in the absence of KCl were considerably higher than at 400 degrees C, especially after 168 hours of exposure. KCl had an effect at shorter exposure times, but after one week the samples exposed with and without KCl had mass gains of comparable magnitude.
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