| 1. |
- Afanas´ev, V.P., et al.
(författare)
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Study of A1/Nb interface by spectroscopy of reflected electrons
- 2007
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 101:064912, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- We have studied Al/Nb interface with help of spectroscopy of reflected electrons. Ion sputtering combined with monitoring of Auger peaks has been used to approach the interface. The developed method of quantitative interpretation of spectra allowed us to characterize the distribution of Al and Nb in the interface region with a nanometer depth resolution. The Al/Nb interface was found to have an intermediate layer of about 10 nm thickness, which is more likely due to the interface roughness, rather than diffusion smearing. We discuss the possibility to distinguish by means of spectroscopy of reflected electrons either material under analysis is a single phase or a mixture of two phases.
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| 2. |
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| 3. |
- Andersson, Petter, 1970, et al.
(författare)
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Field test of superheater corrosion in a CFB waste boiler: Part II - Scale formation characteristics
- 2005
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Ingår i: Materials and Corrosion. - : Wiley. - 0947-5117 .- 1521-4176. ; 56:8, s. 550 - 560
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Tidskriftsartikel (refereegranskat)abstract
- This study concerns the scales formed on the steels T22, Alloy 310, Alloy 28 and the nickel-based Alloy 65 in a superheater test coil at 460-540°C in a CFB waste boiler. The methods used for the characterisation of the scales included SEM, EDX, Auger spectroscopy and XRD. The deposits on the tubes consisted mainly of alkali chlorides and calcium sulphate. The scales formed consisted of Fe 2 O 3 and Fe 3 O 4 on the T22 steel, NiFe 2 O 3 and Cr 2 O 3 on Alloy 310 and Alloy 28, and Cr 2 O 3 and NiO on Alloy 65. Rapid corrosion on the steel T22 was associated with the growth of an open columnar iron oxide below a thick porous chlorine-containing scale. Pitting corrosion on Alloy 310 occurred and it may be associated with selective corrosion, first following the grain boundaries then uniformly attacking the metal. The only protective oxide was observed on Alloy 28 that formed an inner chromium oxide separating the chlorides from the metal. Dense thin chromium oxides were observed in the scale on Alloy 28, but no major cracks were found perpendicular to the tube. Alloy 65 suffered from grain boundary attack and was locally attacked under thick porous chromium oxide with nickel chlorides in the advancing front. Molybdenum was enriched at the interface to the metal on both Alloy 28 and Alloy 65. © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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| 4. |
- Andersson, Petter, 1970, et al.
(författare)
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Scale growth on austenitic alloys under KCl deposits at 500 deg C
- 2008
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Ingår i: Materials Science Forum. - 1662-9752 .- 0255-5476. ; 595-598:I, s. 333-342
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Tidskriftsartikel (refereegranskat)abstract
- The scale growth on two austenitic alloys, Alloy 310 and Sanicro 28, under KCl deposits was examined. This is relevant to the long term corrosion of superheater tubes in biofuel combustion. Coupons were encapsulated in tablets so that 1 mm of KCl with a relative density of 91% covered the metal. Samples were tested at 500 deg C in 5%O2-10%H2O-N2 for 24, 168 and 672 h. After exposure the salt was broken off and the scale was characterised by using SEM-EDX and AES. After 24 h a 50 nm thick oxide surrounded 500 nm thick chromates on the surface. No oxide layer was detected under the chromates and no Cl was found under either layer. The chromate growth requires lateral transportation of Cr along the surface. This reduces the protectiveness of the oxide and accelerates the formation of less protective Fe rich oxides. The formation of chromates also releases HCl inside the KCl tablet. The chromates did not grow significantly between 24 and 168 h, but the oxide grew equally thick beneath and between them and Cl was enriched around the metal oxide interface. After 672 h the oxides were about 5 mum thick and only few chromates were seen. Crystals of KCl formed in areas with thick porous and Fe rich oxides on both alloys.
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| 5. |
- Battabyal, Manjusha, 1979, et al.
(författare)
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Comparison of microstructure in Ni-Al single splats and millimeter sized drops
- 2011
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Ingår i: Surface Modification Technologies XXV. - 9788191057140 ; , s. 3-12
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Konferensbidrag (refereegranskat)abstract
- Splat studies are a central area of research because they can provide fundamental knowledge on the phenomena controlling the final coating properties such as coating microstructure and adhesion. Wetting and heat transfer are expected to influence the final splat shape while they are in turn controlled by the presence of oxides and adsorbed species on the substrate surface. It is however difficult to follow the flattening of a sprayed droplet at the micrometer scale. Since the mid nineties, so-called free falling experiments have been developed with which it is possible to simulate the thermal spray process. The millimetre sized drops allow investigating the flattening and solidification occurring in milliseconds instead of in microseconds.In this study, the microstructure of plasma sprayed Ni-Al splats and millimetre sized droplets produced on TiAlV and pure Ti substrates, respectively, are compared. By use of scanning electron microscopy (SEM), especially the cross-section of splats and droplets has been investigated. In the splats, diffusion across the splat-substrate interface and the formation of an interface layer is detected. In the droplets, up to 3 different layers are formed at the interface to the substrate. The microstructure at the interface and the phases present are discussed and their influence on heat transfer and coating properties are described.In this study, the microstructure of plasma sprayed Ni-Al splats and millimetre sized droplets produced on TiAlV and pure Ti substrates, respectively, are compared. By use of scanning electron microscopy (SEM), especially the cross-section of splats and droplets has been investigated. In the splats, diffusion across the splat-substrate interface and the formation of an interface layer is detected. In the droplets, up to 3 different layers are formed at the interface to the substrate. The microstructure at the interface and the phases present are discussed and their influence on heat transfer and coating properties are described.
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| 6. |
- Cao, Yu, 1969, et al.
(författare)
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Multi-technique characterization of low-temperature plasma nitrided austenitic AISI 304L and AISI 904L stainless steel
- 2014
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Ingår i: Surface and Interface Analysis. - : Wiley. - 1096-9918 .- 0142-2421. ; 46:10-11, s. 856-860
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Tidskriftsartikel (refereegranskat)abstract
- The current study focuses on the characterization of the nitrided layer, formed in American Iron and Steel Institute (AISI) 304L and AISI 904L austenitic stainless steels by industrial low-temperature plasma nitriding, using combined analysis techniques. The study highlighted that the evolution of the microstructure of the nitrided layers is influenced by surface finishing prior to nitriding, alloying elements and nitriding conditions, all factors affecting S-phase formation and nitrogen (N) diffusion mechanisms. The chemical bonding characteristics of Cr 2p3/2 and N 1s as revealed by XPS show a shift in binding energy between expanded austenite (S-phase) and CrN-like compounds. S-phase has proven to be more stable in 904L, whereas residual and/or induced ferrite/martensite in 304L acts as a barrier for its development. © 2014 The Authors.
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| 7. |
- Cao, Yu, 1969, et al.
(författare)
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Role of Nitrogen Uptake During the Oxidation of 304L and 904L Austenitic Stainless Steels
- 2013
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Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 80:5-6, s. 479-491
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen uptake affects corrosion of stainless steel in diesel exhaust systems where urea is injected to reduce NO (x) . This was examined by exposing plasma nitrided 304L and 904L to humid air at 450-600 A degrees C. The samples were characterized primarily by using XRD, AES and XPS. The as-nitrided samples had 10-20 at.% N in 3-40 mu m layers dominated by expanded austenite supersaturated with N, or the S-phase. Nitrogen was detrimental, with oxide thicknesses about 70-100 times thicker than on as-received 304L and 2-5 times thicker on 904L. In the S-phase the Cr activity is reduced by short-range ordering with N, hampering formation of protective oxides. On 304L the fraction of thick oxides decreased significantly with increasing temperature, despite formation of CrN, since formation of bcc promotes Cr diffusion. For 904L the S-phase is more stable and the corrosion less severe due to its alloying content. At 500 A degrees C formation of CrN enhanced the corrosion.
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| 8. |
- Chasoglou, Dimitris, 1982, et al.
(författare)
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Characterization of surface oxides on water-atomized steel powder by XPS/AES depth profiling and nano-scale lateral surface analysis
- 2013
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332. ; 268, s. 496-506
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Tidskriftsartikel (refereegranskat)abstract
- Characterization of oxide products on the surface of water-atomized steel powder is essential in order to determine the reducing conditions required for their removal during the sintering stage which in turn will result in improved mechanical properties. Pre-alloyed powder with 3 wt% Cr and 0.5 wt% Mo was chosen as the model material. Investigation of the powder surface characteristics with regard to composition, morphology, size and distribution of surface oxides was performed using X-ray photoelectron spectroscopy, Auger electron spectroscopy and high resolution scanning electron microscopy combined with X-ray microanalysis. The analysis revealed that the powder is covered by a homogeneous (similar to 6 nm thick) Fe-oxide layer to similar to 94% whereas the rest is covered by fine particulate features with the size below 500 nm. These particulates were further analyzed and were divided into three main categories (i) Cr-based oxides with simultaneous presence of nitrogen, (ii) Si-based oxides of "hemispherical" shape and (iii) agglomerates of the afore mentioned oxides.
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| 9. |
- Cvetkovski, Krste, 1983, et al.
(författare)
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Analysis of wear debris in rolling contact fatigue cracks of pearlitic railway wheels
- 2014
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Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 314:1-2, s. 51-56
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Tidskriftsartikel (refereegranskat)abstract
- In the current study a severe subsurface crack network in a railway wheel has been studied and compared to typical rolling contact fatigue cracks found in the wheel tread surface. Microstructural characteristics, chemical composition and microhardness within the cracks and around crack faces were examined. While the two damage types are principally different, both showed similar crack characteristics, with short cracks branching along the main crack paths and a discontinuous sheared layer of wear debris and metallic flakes within them. Analyses of the wear debris showed that it does not originate from external contamination or being the result of corrosion primarily. Instead it has most likely been produced by shear deformation and wear mechanisms within crack faces caused by mixed-mode crack growth. Although microstructural appearance at lower magnification seemed to differ from the bulk material, at high magnification a lamellar structure was observed consisting of layers of deformed metallic flakes and particles of the base metal. Auger electron spectroscopy was used to analyze these sheared layers; higher concentration of oxygen was measured in between flakes, indicating the presence of oxides and flakes being of similar chemical composition as the base material. A possible explanation is that these layers are created due to high shear forces and friction between crack faces in the service of the wheel. With continued rolling the material being sheared by the cyclic relative motion of the crack faces disintegrates into smaller wear debris particles with concurrent oxidation.
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| 10. |
- Fasth Berglund, Åsa, 1978, et al.
(författare)
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Forskningsintegrerad undervisning: Hur? och Varför?
- 2015
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Ingår i: KUL konferensen.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Lärare som vill integrera forskning i undervisning, och som vill diskutera hur kan detta göras praktiskt, är välkomna på detta runda bordet samtal. Målet med detta är att vi genom denna diskussion får med oss goda exempel, reflektioner och erfarenheter till vidare diskussioner i fakultetsrådet.Då våra utexaminerade ingenjörer utgör viktiga ambassadörer för Chalmers är det strategiskt viktigt att alla studenter får inblick i Chalmers forskning samt att utbildningen är både relevant och aktuell. ‘Chalmers övergripande mål för grundutbildningen är en utbildning i världsklass. Alla studenter ska rustas för att göra skillnad för en hållbar samhällsutveckling. Utbildningarnas struktur och innehåll ska utvecklas i nära samspel med samhälle, näringsliv och vår forskning. Styrkeområdena har som uppgift att integrera utbildning, forskning och nyttiggörande, en integration som också ska prägla utbildningen.’Att integrera forskning i undervisning kan verka enkelt, men är inte utan implikationer. Det finns förstås både för och nackdelar. Schroder skriver att genom att integrera forskning i undervisningen kan detta berika forskarens egen kunskap genom att expandera kontexten (Schroeder, 1996) . Olika kurser kanske lämpar sig olika bra beroende på närhet till forskningen och kopplingen till den undervisande läraren. Man kan tänka sig olika typer av forskningsintegration, alltifrån koppling av kursmaterial till forskningsfronten till mer ”mjuka frågor” om hur det är att jobba som forskare. Målet med detta rundabords-samtal är att vi i denna arbetsgrupp får med oss goda exempel, reflektioner och erfarenheter som vi sedan kan dela med resten av fakultetsrådet under våren 2015.
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