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  • 1.
    Adegoke, Olutayo
    Dalarna University, School of Technology and Business Studies, Material Science.
    Homogenization of Precipitation Hardening Nickel Based Superalloys2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Allvac 718 Plus and Haynes 282 are relatively new precipitation hardening nickel based superalloys with good high temperature mechanical properties. In addition, the weldability of these superalloys enhances easy fabrication. The combination of high temperature capabilities and superior weldability is unmatched by other precipitation hardening superalloys and linked to the amount of the γ’ hardening precipitates in the materials. Hence, it is these properties that make Allvac 718 Plus and Haynes 282 desirable in the manufacture of hot sections of aero engine components.

    Studies show that cast products are less weldable than wrought products. Segregation of elements in the cast results in inhomogeneous composition which consequently diminishes weldability. Segregation during solidification of the cast products results in dendritic microstructure with the segregating elements occupying interdendritic regions. These segregating elements are trapped in secondary phases present alongside γ matrix. Studies show that in Allvac 718Plus, the segregating phase is Laves while in Haynes 282 the segregating phase is not yet fully determined.

    Thus, the present study investigated the effects of homogenization heat treatments in eliminating segregation in cast Allvac 718 Plus and Haynes 282. Paramount to the study was the effect of different homogenization temperatures and dwell time in the removal of the segregating phases. Experimental methods used to both qualify and quantify the segregating phases included SEM, EDX analysis, manual point count and macro Vickers hardness tests.

    Main results show that there is a reduction in the segregating phases in both materials as homogenization proceeds hence a disappearance of the dendritic structure. In Allvac 718 Plus, plate like structures is observed to be closely associated with the Laves phase at low temperatures and dwell times. In addition, Nb is found to be segregating in the interdendritic areas. The expected trend of increase in Laves as a result of the dissolution of the plate like structures at the initial stage of homogenization is only detectable for few cases. In Haynes 282, white and grey phases are clearly distinguished and Mo is observed to be segregating in interdendritic areas.

  • 2.
    Aminul, Mohammad
    Dalarna University, School of Technology and Business Studies, Material Science.
    Inkjet Printing of Adhesives for LCD Products2004Independent thesis Advanced level (degree of Master (Two Years))Student thesis
  • 3.
    Badel, Mbanga
    Dalarna University, School of Technology and Business Studies, Material Science.
    Optical modes for bistable twisted nematic LCD for welding filter applications2003Independent thesis Advanced level (degree of Master (Two Years))Student thesis
  • 4.
    Bengtsson, Linus
    Dalarna University, School of Technology and Business Studies, Material Science.
    Hållfasthetsvariationer i bandände hos varmvalsade höghållfasta stål2005Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [sv]

    Varmvalsade HSLA-stål (high strength low alloy) uppvisar normalt en lägre hållfasthet i sista änden av bandet. Denna s.k. ändeffekt har länge varit känd och flera undersökningar har genomförts för att utvärdera hur mycket de sista metrarna minskar i hållfasthet. Materialet som undersökts i detta examensarbete är Domex 700MC. DX 700MC är ett extra höghållfast kallformningsstål och dess typiska egenskaper är: • Utmärkt formbarhet i förhållande till sin höga hållfasthet. • God svetsbarhet • God slagseghet vid låg temperatur Materialet är varmvalsat och har en minsta sträckgräns längs valsriktningen på 700 MPa. Syfte och problemformulering är: • Bestämma ändeffektens utbredning med hjälp av hållfasthetsprovning • Litteraturstudie om materialmekanismer som inverkar på ändeffekten • Påverkan av värmebehandling • Inverkande tillverkningsfaktorer Examensarbetet är avgränsat till ett material med samma ämnesspecifikation, ÄS, vilket betyder att legeringshalterna i materialet är samma. Dessutom undersöks två olika tjocklekar av färdiga band.

  • 5. Berger, Robert
    et al.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Grehk, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Hörnström, Sven Erik
    A comparative study of the corrosion protective properties of chromium and chromium free passivation methods2007In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 202, no 2, p. 391-397Article in journal (Refereed)
    Abstract [en]

    Commercially available passivation methods for white-rust protection of hot-dip galvanized steel have been investigated. The passivations were either based on trivalent chromium or chromium free. A chromate based conversion coating was used for reference. The treated panels were tested with regard to white rust protection and paintability. The surface chemistry of the conversion coatings was monitored with scanning Auger electron spectroscopy and X-ray photoelectron spectroscopy. Coating thicknesses were measured using Auger electron sputter depth profiling. The passivations were applied with a thickness recommended by the supplier and thus showed large variation. The thickness of the chromium free passivation (Cr-free) is approximately 75 nm. The coating contains the active ions; H3O+, Ti4+, Mn2+, Zn2+, PO4 3-. The passivation based on trivalent chromium (Cr-III) is approximately 30 nm thick and contains the active ions; H3O+ Cr3+, PO4 3-, F. The chromate based passivation (Cr- VI) is approximately 5 nm thick and contains the active ions Cr6+/Cr3+, F-. The Cr-free and the Cr-III passivations showed similar white rust protection in the corrosion tests. The corrosion resistance was good although it did not fully reach the level of the Cr-VI passivation. The results from the tests of the painted panels showed that the powder paint worked well on all three passivations. The solvent born paint worked best on the passivation based on trivalent chromium. The water born paint showed poor resistance to blistering in the Cleveland humidity test for all three passivations. In this test the passivation with hexavalent chromium showed slightly better results than the chromate free passivations.

  • 6.
    Berger, Robert
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Grehk, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Hörnström, Sven Erik
    Properties of Chromate Free Passivations for Hot-Dip Galvanized Steel2006In: CORROSION/2006, San Diego, California, USA, 2006Conference paper (Other academic)
  • 7.
    Berger, Robert
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Stavlid, N.
    Grehk, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    The influence of alkali-degreasing on the chemical composition of hot-dip galvanized steel surfaces2006In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 38, no 7, p. 1130-1138Article in journal (Refereed)
    Abstract [en]

    The influence of dipping temperature and time on the surface chemistry of hot-dipped galvanized steel sheets during the alkaline degreasing process is investigated. The surface chemistry was monitored with scanning Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectroscopy (ToF-SIMS). The results show high Al concentrations on the untreated surfaces, which are significantly reduced during alkaline degreasing. The same conclusions could be drawn for the carbon compounds that accumulate on the surface during storage. The measurements reveal a gradual reduction in surface Al as the alkali solution temperature and/or degreasing time are increased. When degreasing was conducted at 70 °C for 30 s the surface was practically free from Al, which was present only in small islands. Furthermore, the experiments showed that the thickness of the oxide film covering the surfaces before and after alkaline degreasing is approximately 20 Å. The main constituents of the film varied from ZnAl hydroxide/oxide to Zn hydroxide/oxide, before and after degreasing, respectively. 

  • 8.
    BERGKVIST, ALEXANDER
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    LARSSON, GUSTAV
    Dalarna University, School of Technology and Business Studies, Material Science.
    Sprickbildning under formning av varmförzinkat stål: Crack formation during forming of zinc-coated steel2007Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    Stålplåt varmförzinkas för att ge ett bra korrosionsskydd. Det är dock svårt att bearbeta varmförzinkade stålplåt t.ex. att rullforma p.g.a. att Fe-Zn faser som bildas på ytan vid varmförzinkning är sprödare än stålet. Detta ger upphov till sprickbildning i beläggningen vid bockning vilket medför försämringar i korrosionsskyddet. Farligast är de sprickor som går igenom alla faser. Syftet med denna rapport var att ta reda på om det är möjligt att rullforma u-balkar av varmförzinkad plåt. För att ta reda på hur mycket beläggningen spricker vid olika stora töjningar bockades små varmförzinkade plåtbitar. Med hjälp av SEM och LOM jämfördes antalet sprickor vid olika stora bockningsvinklar. Vid stora töjningar sågs en kraftig sprickbildning och flera sprickor som gick igenom alla faserna. Försök gjordes för att undersöka om sprickbildningen minskade vid bockning under en förhöjd temperatur. Bockningar utfördes vid 200, 250 och 300°C. En tydlig minskning i antalet sprickor i beläggningen kunde observeras, framförallt sprickorna i det yttersta zinklagret. Vid rullformning finns det risk att zinkbeläggningen fastnar på rullformningsverktyget (galling). Detta kan framförallt förväntas om rullformningen sker vid förhöjd temperatur. Ett enkelt repprovningsförsök utfördes vid 250°C temperatur för att ta reda på hur mycket som fastnar. En vanlig stålkula och en WCC-belagd kula testades och WCC-beläggningen gjorde att galling minskade avsevärt.

  • 9. Bergström, Yngve
    et al.
    Granbom, Ylva
    Dalarna University, School of Technology and Business Studies, Material Science.
    Sterkenburg, Dirk
    A dislocation based theory for the deformation hardening behavior of DP steels: Impact of martensite content and ferrite grain size2010In: Journal of Metallurgy, ISSN 1687-9465Article in journal (Refereed)
    Abstract [en]

    A dislocation model, accurately describing the uniaxial plastic stress-strain behavior of dual phase (DP) steels, is proposed and the impact of martensite content and ferrite grain size in four commercially produced DP steels is analyzed. It is assumed that the plastic deformation process is localized to the ferrite. This is taken into account by introducing a non-homogeneity parameter, f(e), that specifies the volume fraction of ferrite taking active part in the plastic deformation process. It is found that the larger the martensite content the smaller the initial volume fraction of active ferrite which yields a higher initial deformation hardening rate. This explains the high energy absorbing capacity of DP steels with high volume fractions of martensite. Further, the effect of ferrite grain size strengthening in DP steels is important. The flow stress grain size sensitivity for DP steels is observed to be 7 times larger than that for single phase ferrite.

  • 10.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Surface Characterisation Using ToF-SIMS, AES and XPS of Silane Films and Organic Coatings Deposited on Metal Substrates2003Doctoral thesis, monograph (Other academic)
  • 11.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Berger, Robert
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Grehk, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Sundell, Per-Erik
    Johansson, Mats
    Bonding of vegetable oils to mercapto silane treated metal surfaces: surface engineering on the nano scale2006In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, no 2, p. 838-841Article in journal (Refereed)
    Abstract [en]

    In this paper the bonding of thin vegetable oil films on mercapto silane treated aluminium surfaces has been studied. The silane molecules are attached to the surface by metal–oxygen–silicon bonds. The coupling between the unsaturated bonds of the vegetable oil and the thiol functionalised surface was obtained through a photoinduced thiol-ene reaction. The surfaces were characterised by X-ray photoelectron spectroscopy (XPS). Vegetable oil contains both saturated and unsaturated carbon chains. For the reactions investigated in this study it is the unsaturated carbon chains that can react by a thiol-ene reaction and the results indicate that it is possible to attach a vegetable oil to a metal surface pre-treated with a thiol functionalised silane.

  • 12.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Carlsson, Per
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Characterisation of Thin Films of a Non-Organofunctional Silane on Al-43.4Zn-1.6Si Alloy Coated Steel by ToF-SIMS1999In: SIMS XII, Brussels, Belgium, 1999Conference paper (Refereed)
  • 13.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Carlsson, Per
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Tribological Characterisation of an Organic Coating by the use of ToF-SIMS2003In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 203-204, p. 596-599Article in journal (Refereed)
    Abstract [en]

    ToF-SIMS has been used to analyse tribological induced chemical changes of organic coatings deposited on steel strip hot-dip coated with a 55.0% Al–43.4% Zn–1.6% Si alloy (Aluzink). The organic coating was a styrene–acrylic co-polymer containing different forming additives. The forming properties of the organic coatings were evaluated with modified scratch testing. The friction curves show that organic coated hot-dip coated steel displays significantly better tribological properties, i.e. lower coefficient of friction and lower wear, as compared to hot-dip coated steel. Furthermore, the organic coatings showing the highest material transfer tendency also show the highest wear. ToF-SIMS spectra show that a transfer film consisting of species from the organic coating is formed on the ball counter surface. Finally, a combination of SEM and ToF-SIMS analysis shows that mechanical failure of the coating dominates, i.e. no tribochemical changes of the coatings could be detected in the wear track.

  • 14.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Grehk, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    A corrosion study of hot-dip galvanized steel sheet pre-treated with gamma-mercaptopropyltrimethoxysilane2007In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 201, no 8, p. 4734-4742Article in journal (Refereed)
    Abstract [en]

    In the present work an organofunctional silane, gamma-mercaptopropyltrimethoxysilane (gamma-MPS), has been deposited on hot-dip galvanized cold rolled steel from different silane solution concentrations. Painted and unpainted silane treated samples were corrosion tested and painted samples were adhesion tested. The surface chemistry of the unpainted silane treated samples was investigated with AES, ToF-SIMS and EDS and the surface morphology was studied with SEM. The results show that the silane film thickness is dependent on the silane concentration in the silane solution and a higher silane concentration gives a thicker film. Moreover, thicker films tend to give films with a pronounced crack pattern and even detachment of film debris. Corrosion tests of unpainted samples show that gamma-MPS can not work as a passivation treatment but gives a very good adhesion to the paint

  • 15.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Grehk, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Gelius, Ulrik
    XPS and AES Characterisation of hydrolysed ?- Mercaptopropyltrimethoxysilane deposited on Al, Zn and Al-43.4Zn-1.6Si alloy coated steel2004In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, no 36, p. 624-631Article in journal (Refereed)
  • 16.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Characterisation of a Non-Organofunctional Silane Film Deposited on Al, Zn and Al-43.4Zn-1.6Si Alloy Coated Steel, Part II. Interfacial Characterization by ToF-SIMS and AES2001In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 31, no 3, p. 223-231Article in journal (Refereed)
    Abstract [en]

    Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been used to analyse the interface between a non-organofunctional silane and three different metal substrates (aluminium, zinc and an aluminium-zinc alloy). Ion etching using Ga+ ions was used to expose the interfacial region. Ion fragments from the samples were examined carefully where supposed metal-oxygen-silicon ion fragments should appear in the mass spectra. From high mass resolution spectra it was concluded that there exists an AlOSi+ ion fragment at nominal mass m/z = 71 amu on the aluminium and aluminium-zinc alloy substrates and a ZnOSi+ ion fragment at nominal mass m/z = 108 amu on the zinc and aluminium-zinc alloy substrates. These results are further enhanced by the fact that the characteristic ion pattern of ZnOSi+-type ion fragments, composed of different naturally stable zinc and silicon isotopes, in the mass range m/z = 108-112 amu showed the expected relative peak height relations. The presence of these metal-oxygen-silicon ion fragments is a strong indication that chemical interaction between the silane and the metal substrates exists and that the nature of this interaction is due to the formation of a covalent bond between the silane and the metal substrate. Copyright © 2001 John Wiley & Sons, Ltd.

  • 17.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Characterisation of a Non-Organofunctional Silane Film Deposited on Al, Zn and Al-43.4Zn-1.6Si Alloy-Coated Steel, Part I. Surface Characterization by ToF-SIMS2001In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 31, no 3, p. 212-222Article in journal (Refereed)
    Abstract [en]

    The need to develop new environmentally friendly pretreatments in the surface engineering of metal substrates has become more and more important.This is mainly due to the toxic and carcinogenic properties of the chromium-based surface pretreatments frequently used in the industry. During the last decade, simple solution-dip silane-based pretreatments have emerged as promising candidates for the replacement of currently used pretreatments of metals. Recent investigations have shown that the performance of these newly developed pretreatments is strongly dependent on the chemical composition and structure of the silane film and consequently a lot of work, based on advanced surface analytical techniques, is needed in order to characterize these properties. In the present study, time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been used to characterize the structure of thin films of the non-organofunctional silane 1,2-bis(triethoxysilyl)ethane (BTSE) deposited on three different metal substrates, i.e. Al, Zn and Al-43.4Zn-1.6Si (AlZn) alloy-coated steel. Of special interest was an evaluation of the influence of substrate material on the structure and composition of the silane films. The results show that the BTSE silane forms a thin, evenly distributed film over the substrate surfaces and that the molecular structure of the silane film is independent of the type of metal substrate. Analysis of the molecular ions in the positive mode shows that the surface structure of the BTSE silane is very complex and that the BTSE condensates via one to three SiOSi bridges. Also, the results show that the BTSE silane is not fully hydrolysed using a hydrolysing time of 1 h. Finally, if an alcohol is used as a solvent for the BTSE there is a clear chemical interaction between the alcohol and the silane, resulting in an exchange of alkoxy groups between the alcohol and the silane. Copyright © 2001 John Wiley & Sons, Ltd.

  • 18.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Time-of-Flight SIMS Characterization of Hydrolysed Organofunctional and Non-Organofunctional Silanes Deposited on Al, Zn and Al-43.4Zn-1.6Si Alloy-Coated Steel2003In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 35, no 11, p. 880-887Article in journal (Refereed)
  • 19.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Jani, Simon
    AB Sandvik Materials Technology, Sandviken, Sweden.
    Lundberg, Mats W.
    AB Sandvik Materials Technology, Sandviken, Sweden.
    Initial oxidation of ferritic interconnect steel, effect due to a thin ceria coating2012In: European Fuel Cell Forum 2012 - Proceedings (memory stick), 2012Conference paper (Other academic)
    Abstract [en]

    Today there exist many ferritic stainless steel grades with a chemical composition speciallydesigned to be used as interconnects in solid oxide fuel cell applications in a temperatureinterval of 650-850°C. The steels have good high temperature mechanical properties andcorrosion resistance as well as good electron conductivity in the formed chromium oxidescale.One way to substantially decrease the high temperature degradation of the interconnectsteel i.e. improve properties such as increased surface conductivity and decreasedoxidation and chromium evaporation is to coat the interconnect steel with suitablecoatings. Today it is well known that a thin cobalt coating hinders chromium evaporationand a ceria coating lowers the oxidation rate at high temperature. Thus, by coating theinterconnect steel the properties are improved to an extent that it should be possible to usea cheaper standard steel, e.g. AISI 441, as substrate for the coatings.In this study the ferritic stainless steel alloys Sandvik Sanergy HT and AISI 441 is oxidizedin laboratory air at temperatures at 750°C, 800°C and 850°C. The results show that a welladhered oxide scale of a complex layered structure is formed with significant amounts ofMn, Fe, Cr and Ti in the oxide scale. A Ce coating significantly reduces the growth rate ofthe oxide scale. The lower Cr content in the AISI 441 alloy does not affect the initial hightemperature corrosion properties when coated with Ce. Also, the results demonstrate theusefulness of ToF-SIMS depth profiling for characterisation of the initial stages of oxidationof SOFC materials.

  • 20.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Johansson, M
    Samuelsson, J
    Sundell, P.-E
    A Tribological Study of a Novel Pre-Treatment With Linseed Oil Bonded to Mercaptosilane Treated Aluminium2003In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, no 166, p. 141-152Article in journal (Refereed)
  • 21.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Johansson, M
    Sundell, P.-E
    Carlsson, Per
    Dalarna University, School of Technology and Business Studies, Material Science.
    Hellsing, Magnus
    Dalarna University, School of Technology and Business Studies, Material Science.
    A ToF-SIMS Study of Linseed Oil Bonded to Mercaptosilane Treated Aluminium2003In: Proceedings of the 14th International Conference on Secondary Ion Mass Spectrometry, SIMS XIV, San Diego, California, USA, 2003Conference paper (Refereed)
  • 22.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Schuisky, Mikael
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Scratch testing as a tool to evaluate the adhesion of thermally grown oxides on ferritic interconnect steel2010In: 2010 Conference Memory Stick 9th European SOFC Forum, Lucerne, 2010Conference paper (Other academic)
    Abstract [en]

    The attempt to decrease the temperature in solid oxide fuel cells has made it possible to use metallic materials as interconnect, i.e. the part that separates the anode and the cathode in a fuel cell stack. Besides being impermeable to gases the interconnect give good electron conduction between adjacent cells and to the external circuit. Thus, the unavoidable oxide scale must have good electron conductivity and therefore good adhesion to the metal since spalling of the oxide scale from the metal will give rise to higher resistance in the whole oxide scale metal system. Scratch testing is today a common technique in order to characterize the mechanical properties of thin hard coatings on various types of substrate materials. In this test the normal load applied on the scratching stylus is continuously increased while the stylus is moved relative the surface. The critical load, corresponding to a cohesive and/or adhesive coating failure is registered either by a change in the force, the acoustic emission signal or preferable by combining the information from signals with post-test characterisation of the scratch using scanning electron microscopy. The present study evaluates the possibilities to use scratch testing as a method to measure or at least quantitatively classify the adhesion characteristics of different types of oxide scales thermally grown on ferritic stainless interconnect steel. Both uncoated and interconnect steel pre-coated with thin metallic coatings are studied. The results show that all oxide layers investigated display a sufficient cohesive strength and adhesion to the underlying substrate and that the major scratching induced surface failure mechanisms are plastic deformation and cracking, i.e. no brittle like chipping or spalling could be observed.

  • 23.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Schuisky, Mikael
    Ravash, Hamed
    Froitzheim, Jan
    Svensson, Jan-Erik
    Chromium evaporation from plastically deformed pre-coated Sandvik Sanergy HT 22% Cr ferritic interconnect steel2010In: 2010 Conference Memory Stick 9th European SOFC Forum, Lucerne, 2010Conference paper (Other academic)
    Abstract [en]

    Ferritic stainless steel has attracted a great deal of attention for its use as an interconnector in solid oxide fuel cells (SOFCs). The ferritic Sandvik Sanergy HT chromium steel is specially developed for interconnectors in SOFC with a unique chemical composition, which gives the alloy a good high temperature corrosion resistance as well as good surface conductivity in the formed chromium oxide scale. However, chromium evaporation from metallic interconnectors in SOFC fuel cells tends to poison the cathode of the fuel cell. Furthermore, the evaporation of chromium species from the oxide surface tends to increase the oxidation rate resulting in increased contact resistance. It is nowadays well known that thin coatings of e.g. cobalt can substantially reduce the chromium evaporation from the interconnectors. In this study, a 22% Cr ferritic steel, Sandvik Sanergy HT has been coated with a thin metallic cobalt film. The coated material was plastically deformed and the effect of chromium evaporation was studied as a function of the degree of deformation. Coated samples are also compared to uncoated material. The results show that the metallic cobalt film cracks when the steel sheet is formed but the chromium evaporation is more or less unaffected.

  • 24.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Stanciu, V.
    Warnicke, P.
    Östh, M.
    Svedlindh, P.
    ToF-SIMS depth profiling of (Ga,Mn)As capped with amorphous arsenic: effects of annealing time2006In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, no 19, p. 7252-7254Article in journal (Refereed)
    Abstract [en]

    The influence of annealing time on an amorphous As cap layer and the depth distribution of Mn atoms have been investigated. The results show that a 1600 Å thick As cap layer is completely desorbed after 3 h of annealing time. The depth distributions of Mn indicate that interstitial Mn atoms have diffused to the outer surface and being passivated. The thickness of the Mn passivation layer was around 90 Å.

  • 25. Birgerson, J.
    et al.
    Lindsjö, A.
    Selo Mustafa, Muhammed
    Dalarna University, School of Technology and Business Studies, Material Science.
    Grehk, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    Spectroscopic study of chemically stabilized dichroic thin crystal films2004In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 236Article in journal (Refereed)
  • 26. Birgerson, J.
    et al.
    Osterman, Jesper
    Dalarna University, School of Technology and Business Studies, Material Science.
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    Possibilities for high pretilt bistable twisted nematics2002In: Eurodisplay 2002, Nice, France, 2002Conference paper (Refereed)
  • 27.
    Birgerson, Jonas
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Keil, M
    Luo, Y
    Ågren, H
    Salaneck, W.R
    A study of the electronic structure of ethylenedioxythiophene in gasphase using NEXAFS and quantum chemical calculations2004In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, no 392, p. 100-104Article in journal (Refereed)
  • 28.
    Birgerson, Jonas
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Lindsjö, A
    Selo Mustafa, Muhammed
    Dalarna University, School of Technology and Business Studies, Material Science.
    Grehk, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    Spectroscopic study of chemically stabilized dichroic thin crystal films2004In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, no 236, p. 444-450Article in journal (Refereed)
  • 29.
    Birgerson, Jonas
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Selo Mustafa, Muhammed
    Dalarna University, School of Technology and Business Studies, Material Science.
    Lindsjö, A
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    Stabilization of Thin Crystal Film Polarizers for LCD's2004In: Proceedings of SID 2004, Seattle, USA, 2004, p. 590-593Conference paper (Refereed)
  • 30.
    Bjöör, Robert
    Dalarna University, School of Technology and Business Studies, Material Science.
    Analys av tjocklekspikar på höghållfast tunnplåt: Evaluation of ridges in high strength steel sheet2006Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [sv]

    I SSAB Tunnplåts kallvalsverk, Tandemverket, uppstår ibland korta tjockleksvariatoner längs bandet som reglersystemet inte hinner korrigera. Dessa tjockleksfel som uppstår på kallvalsade band har getts namnet tjocklekspikar och drabbar främst tre olika ämnessammansättningar med hög kiselhalt. Genom analys av mätdata har ett tydligt samband identifierats mellan tjocklekspikarna och temperaturvariationer i bandets längsriktning varmvalsningsprocessen. En närmare analys visade på stora skillnader i materialegenskaper mellan det som identifierats som pikbenägna områden gentemot kringliggande referensmaterial. Det betraktade pikområdet hade en tydligt bainitisk struktur, jämfört med den förväntade ferritiska strukturen som erhölls i referensområdet. Med utökad temperaturmätning och videofilmning kunde uppkomsten av pikarna fastställas. I väntan på kommande stick i det reversibla förparet, låg hetan still och utsattes för en tämligen kraftig kylning på grund av rullbanans anliggande rullar. Som en konsekvens av kylningen har pikområdena utsatts för en snabbare och kraftigare underkylning i kylsträckan som i sin tur har resulterat i en bainitstruktur. Hypotesen har byggt på att temperatursänkningen orsakad av rullbanan har påverkat resultatet vid färdigvalsningen, där den lägre temperaturen i pikområdena orsakat en partiell fasomvandling. I kylsträckan har endast den återstående austeniten fasomvandlats vilket har resulterat i att inte lika stor mängd omvandlingsvärme genererats, vilket skulle ha varit fallet utan den partiella fasomvandlingen. På så vis har en kraftigare underkylning kunnat ske, vilken i sin tur har givit en hård bainitisk struktur som vid valsning i kallvalsverket skulle komma att orsaka tjocklekspikar.

  • 31. Blinov, L.
    et al.
    Kozlovsky, M.
    Ozaki, M.
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    Yoshino, K.
    Photo-induced dichroism and optical anisotropy in a liquid crystalline azobenzene side chain polymer caused by anisotropic angular distribution of trans and cis isomers1998In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 84Article in journal (Refereed)
  • 32. Blomberg, Jonas
    et al.
    Persson, Bengt
    Dalarna University, School of Technology and Business Studies, Material Science.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Effects of semi-isostatic densification on anatomy and cell-shape recovery on soaking2006In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 60, no 3, p. 322-331Article in journal (Refereed)
    Abstract [en]

    Images obtained by scanning electron microscopy (SEM) helped to clarify the question as to how anatomy influences the deformation on compression and the spring-back of densified wood on water soaking. Transverse sections of Norway spruce (Picea abies), Scots pine (Pinus sylvestris), black alder (Alnus glutinosa), Swedish aspen (Populus tremula), European birch (Betula pubescens), European beech (Fagus sylvatica) and pedunculate oak (Quercus robur) were studied. Wood is reinforced with rays in the radial direction and with dense latewood in the tangential direction. When strained radially, rays buckle or tilt tangentially. Softwoods were mainly compressed radially, owing to low number of rays and since latewood is much denser than earlywood. The diffuse-porous hardwoods with low density variation between latewood and earlywood were mainly deformed tangentially, except birch, which has high density at the annual ring border and is mainly compressed radially. The ring-porous hardwoods were relatively equally deformed in the radial and tangential directions because of the high number of rays and high latewood density. Moisture-induced spring-back (shape recovery) was proportional to the degree of compression. Rays remained deformed, which also influenced the surrounding wood. Longitudinal wood cells almost resumed their original shape. Wood with low density and a low degree of compression showed the highest structural recovery. Shearing deformation was particularly pronounced and permanent in woods with high strength anisotropy. Thin-walled and sheared cells, such as earlywood in softwood, tended to crack on compression. Cracks usually stopped at the middle lamella and had a lesser influence on strength properties than for lumen-to-lumen cracks.

  • 33.
    Bonam, Sudhakar
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Kishore, Tatineni
    Dalarna University, School of Technology and Business Studies, Material Science.
    Automation of Four Point Probe by using Lab VIEW Programming2004Independent thesis Advanced level (degree of Master (Two Years))Student thesis
  • 34. Borgström, Henrik
    et al.
    Harlin, Peter
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Paiar, Tomaso
    Wang, Yu
    Nyborg, Lars
    Possibilities and constraints of implementing starch consolidated high speed steel in prototyping2008In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 475, no 1-2, p. 34-38Article in journal (Refereed)
    Abstract [en]

    In the starch consolidation (SC) process, a water-based slurry containing powder, starch, dispersant and thickener is used to fabricate near net-shape green bodies that are de-binded and further consolidated by sintering. In this study, gas atomized M3/2 as well as high and low carbon V-rich M4 type high speed steel powder (<150 mu m) are considered, Both material types undergo high volumetric shrinkage during super-solidus liquid phase sintering enabling them to reach near full density. The analyses and the review cover different process aspects like: recipe optimisation, post-gelatinization drying, de-binding and sintering. A SC recipe consisting of 58 vol.% powder, 3 vol.% starch, 1 vol.% dispersant and a thickener solution resulted in a density of >98% than what is theoretically stated after sintering. It is found that the success of the post-gelatinization drying procedure depends on the smoothness of mould material and controlling powder oxidation. The best combination was freeze drying the slurry in a silicon rubber mould. For V-rich alloys a total or partial control of eutectic carbides in the final microstructure could be realized for vacuum and nitrogen sintering atmospheres, respectively.

  • 35. Borgström, Henrik
    et al.
    Paiar, T
    Harlin, Peter
    Dalarna University, School of Technology and Business Studies, Material Science.
    Nyborg, Lars
    Super-solidus Liquid Phase Sintering of Starch Consolidated M4 High Speed Steel Powder2005In: EPMA 2005, Prague, 2005Conference paper (Other academic)
  • 36.
    Bäcke, Linda
    Dalarna University, School of Technology and Business Studies, Material Science.
    Modeling the effect of solute drag on recovery and recrystallization during hot deformation of Nb microalloyed steels2010In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, no 2, p. 239-247Article in journal (Refereed)
    Abstract [en]

    The effect of solute drag on recovery and recrystallization during hot deformation of Nb microalloyed steels has been modeled using a newly developed microstructure model. The model is based on dislocation theory and the calculated dislocation density determines the driving force for recrystallization. Subgrains act as nuclei for recrystallization and have to reach a critical size and configuration in order for recrystallization to start. In the model, the solute drag effect of Nb in solution is described. Nb retards both dislocation and grain boundary movement giving retardation in both recovery and recrystallization. Calculations were compared to experimental results from axisymmetric compression tests combined with stress relaxation. In order to model the effect of solute drag, the experiments were carried out at temperatures where precipitation of Nb(C, N) should not occur. The calculated flow stresses for the compression tests show good fit with experimental data. Also, the calculated results of the relaxation tests show good agreement with experimental data.

  • 37.
    Böe, Markus
    Dalarna University, School of Technology and Business Studies, Material Science.
    Processens inverkan på den dragna stångens rakhet samt dragskivans slitage2005Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    Examensarbetets syfte var att undersöka vilka parametrar som har störst inverkan på rakheten i processen dragen stång, med avseende på kortvågighet samt vilka faktorer som har störst inverkan på dragskivans slitage. Materialet som undersöktes var OVAKO 803 D som är en storvolymsprodukt, 6 stycken trådringar testades varav 3st var valsad tråd och resterande 3 st skalsvarvade. Parametrar som undersöktes var dragkonans vinkel, bärningens längd och övergångsradien mellan dessa. Statistisk försöksplanering med fullständigt faktorförsök har använts.

  • 38. Canovic, Sead
    et al.
    Engkvist, Josefin
    Lai, Haiping
    Götlind, Helena
    Svensson, Jan-Erik
    Johansson, Lars-Gunnar
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Microstructural investigation of the water vapour effect on the oxidation of the FeCrAl alloy Kanthal AF at 600 and 800 C2008In: 214th Meeting of ECS - The Electrochemical Society, Honolulu, Hawaii, 2008Conference paper (Other academic)
  • 39. Canovic, Sead
    et al.
    Engkvist, Josefin
    Dalarna University, School of Technology and Business Studies, Material Science.
    Liu, Fang
    Götlind, Helena
    Hellström, Kristina
    Svensson, Jan-Erik
    Johansson, Lars-Gunnar
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Halvarsson, Mats
    Microstructural investigation of the initial oxidation of the FeCrAlRE alloy Kanthal AF in dry and wet O2 at 600 and 800°C2010In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 157, no 6, p. C223-C230Article in journal (Refereed)
    Abstract [en]

    The FeCrAlRE (where RE is reactive element) alloy Kanthal AF was exposed isothermally at 600 and 800°C for 72 h in dry O2 and in O2 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°C, while no significant effect was observed at 600°C. A thin two-layered oxide formed at 600°C: an outer (Fe,Cr)2O3 corundum-type oxide, containing some Al, and an inner, probably amorphous, Al-rich oxide. At 800°C a two-layered oxide formed in both environments. The inner layer consisted of inward grown a-Al2O3. In dry O2 the originally formed outward grown g-Al2O3 had transformed to a-Al2O3 after 72 h. Water vapor stabilized the outward grown g-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°C the Y-rich RE particles were surrounded by thick oxide patches in both dry and humid O2.

  • 40.
    Carlsson, Per
    Dalarna University, School of Technology and Business Studies, Material Science.
    Surface engineering in sheet metal forming2005Doctoral thesis, monograph (Other academic)
  • 41.
    Carlsson, Per
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Hörnström, Sven Erik
    Corrosion Behaviour of Aluzink with Different Passivation Treatments2001In: GALVATECH 2001, Brussels, Belgium, 2001Conference paper (Other academic)
  • 42.
    Carlsson, Per
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Automatic Scratch Testing - A New Tool for Evaluating the Stability of Tribological Conditions in Sheet Metal Forming2001In: GALVATECH 2001, Brussels, Belgium, 2001Conference paper (Other academic)
  • 43.
    Carlsson, Per
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Friction and Wear Mechanisms of Thin Organic Permanent Coatings Deposited on Hot-Dip Coated Steel2001In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 247, no 1, p. 88-99Article in journal (Refereed)
    Abstract [en]

    Adhesive wear, generally defined as ‘wear due to localised bonding between contacting solid surfaces leading to material transfer between the two surfaces or loss from either surface’ is a common phenomenon in many sliding contact tribosystems, e.g. sheet metal forming operations. In these operations, galling, i.e. seizure of the sheet surface caused by transfer of sheet material to the tool surface, is frequently a problem since it may results in scratching of the formed sheet surface and eventually cracking and fracture of the product due to high friction forces. In order to reduce the coefficient of friction and the galling tendency in sheet metal forming operations thin organic coatings has been introduced on the market with the intention of improving the performance of hot-dip coated steel sheet. In summary, these coatings have the potential to increase the formability without additional lubrication and serve as temporary corrosion protection during transportation. In the present study, the friction and wear mechanisms of five different thin organic permanent coatings deposited on hot-dip coated (Zn and 55% Al–Zn) steel sheet is evaluated by modified scratch testing. The results obtained show that this test method permits easy and reproducible evaluation of the tribological properties of thin organic coatings. Further, these coatings show a high potential when it comes to improve the formability of hot-dip coated steel. The results obtained are discussed in relation to the identified friction and wear mechanisms.

  • 44.
    Carlsson, Per
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Tribological Behaviour of Thin Organic Permanent Coatings Deposited on Hot-Dip Coated Steel Sheet - a Laboratory Study2000In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 132, no 2-3, p. 169-180Article in journal (Refereed)
    Abstract [en]

    The forming and handling of hot-dip coated steel sheets is frequently associated with problems such as galling, scratching and discoloration. Recently, a new generation of thin organic coatings has been introduced on the market in order to improve the performance of hot-dip coated steel sheets and reduce these kinds of problems. In summary, these coatings have the potential to increase the formability of the steel sheet without additional lubrication, the anti-finger print properties and the corrosion protection of the product. Besides, they should also provide a pre-treatment for painting, i.e. they can be classified as permanent coatings. In the present study, the tribological behaviour of three different thin organic permanent coatings deposited on hot-dip coated (pure zinc and 55% Al–Zn) steel sheets is evaluated by three different laboratory tests; modified scratch testing, pin-on-disc testing and bending under tension testing. The results obtained show that all tests yield consistent and valuable information concerning the friction and wear properties of the materials and can, therefore, be used in order to study the tribology in sheet metal forming and the performance of different types of permanent coatings. Of the permanent coatings investigated, a pure organic coating shows the lowest coefficient of friction (µ close to 0.1) and the highest wear resistance, thus offering excellent anti-galling properties. In contrast, a mixed organic/inorganic coating displays a relatively high coefficient of friction (µ close to 0.3) and a significantly lower wear resistance. Surface analyses of the tested surfaces show that the thickness and coverage of the thin organic coating play an important role in controlling friction and wear. Furthermore, a thin organic coating optimized for improved formability and handling should display: a high adhesion to the underlying substrate material, a low coefficient of friction, a high load carrying capacity and a high intrinsic wear resistance.

  • 45.
    Carlsson, Per
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Tribological Performance of Thin Organic Permanent Coatings Deposited on 55%Al-Zn Coated Steel – Influence of Coating Composition and Thickness on Friction and Wear2001In: Wear, ISSN 0043-16.48, Vol. 251, no 1-12, p. 1075-1084Article in journal (Refereed)
    Abstract [en]

    Dry lubricants are today increasingly being used in various types of sheet metal forming operations. Among these, permanent coatings, based on organic resins are the only lubricants which have the potential to increase the formability without additional lubrication, serve as temporary corrosion protection during transportation and, finally, serve as a pre-treatment before subsequent painting. In the present study, the influence of coating composition and thickness on the friction and wear behaviour of different thin organic permanent coatings deposited on 55%Al–Zn coated steel sheet have been evaluated by various types of laboratory tests. Surface profilometry, scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and time-of-flight secondary ion mass spectrometry (ToF–SIMS) were used in order to characterise and model the tribological behaviour of the coatings. The results obtained show that the tribological properties of thin organic permanent coatings are strongly influenced by the coating thickness. In order to reduce problems associated with high friction and galling, the coating must be deposited with a uniform thickness, i.e. uncoated regions must be avoided. Furthermore, the addition of various types of additives can be used in order to further improve the tribological performance of these types of coatings.

  • 46.
    Carlsson, Per
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Klang, Hans
    A study of the initial stages of atmospheric corrosion of formed hot dip zinc coated steel1997In: EUROCORR-97, Trondheim, Norway, 1997Conference paper (Other academic)
    Abstract [en]

    Hot-dip zinc coated steel sheet is extensively used to improve the corrosion protection of steel constructions. When the sheet is formed cracks in the zinc coating develop in strained areas. The zinc coating gives a galvanic protection of the steel in damaged areas of the coating and at cut edges of the sheet. The degree of protection is, however, dependent on factors such as the geometry and the area of the defects, the coating thickness, the presence of corrosive ions in the electrolyte and the wet time. In this work we have studied the initial atmospheric corrosion of zinc coated steel in defects on bended and scribed material. The samples were exposed to a cyclic indoor corrosion test developed by Volvo (Volvo standard 1027). Scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS) and Auger electron spectroscopy (AES) were used to monitor the initial stages of corrosion and the growth of corrosion products. The corrosion products were identified as predominantly zinc hydroxycarbonate, zinc hydroxychloride and zinc hydroxide. The amount of corrosion products increases with the size of the damaged area, which suggests that the cathodic reduction of oxygen at the steel substrate controls the corrosion rate.

  • 47.
    Carlsson, Per
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Klang, Hans
    Initial Atmospheric Corrosion Behavior of Formed Hot Dip Zinc Coated Steel - An Energy Dispersive X-ray Spectroscopy Study1997In: SCANDEM-97, Gothenburg, Sweden, 1997Conference paper (Other academic)
  • 48. Carlsson, Per
    et al.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    PVD coatings for sheet metal forming: a tribological evaluation2006In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 200, no 14-15, p. 4654-4663Article in journal (Refereed)
    Abstract [en]

    The use of liquid-based lubricants in sheet metal forming mutually has a negative impact on the environment and on the whole economy, and, consequently, there is an urgent need to find a solution to make the forming processes dry or nearly dry. The deposition of a low-friction PVD coating on the forming tool has during the last years proved to be an interesting choice when it comes to create an “unlubricated” forming process. In the present study, five different PVD coatings (one CrN and four metal-carbide-doped DLC coatings) have been evaluated in sliding contact against hot dip Zn and 55% Al–Zn-coated steel sheet using a ball-on-disc test. From the investigation, it was found that all DLC coatings have potential to prevent material pickup during dry forming of hot dip Zn-coated steel. However, the as-deposited surface morphology, showing surface irregularities such as droplets and dimples, of the coatings will strongly influence the tribological performance, and, consequently, a polishing treatment or a running-in process, resulting in a smooth surface, will significantly reduce the tendency to material pickup. In sliding contact against 55% Al–Zn-coated steel, all PVD coatings display material pickup and high friction values, the only exception being a CrC-doped DLC coating in the as-polished condition. The CrN coating showed poor performance in sliding contact against both steel sheet materials due to a high tendency to material pickup. The study focuses on the tribo-induced changes of the surface condition of the PVD coating and the steel sheet surface during the sliding event. The changes in surface chemistry and topography of the tribo surfaces were characterised using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Auger electron spectroscopy (AES) and light interference profilometry.

  • 49.
    Carlsson, Rickard
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Sten, Niklas
    Dalarna University, School of Technology and Business Studies, Material Science.
    Varmsmidning av aluminiumlegering 6026 T9: Warm forging of aluminum alloy 6026 T92011Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    In this project forging of aluminum alloy Al 6026 T9 has been performed in the temperature range of 400 °C – 470 °C. The alloy which was in the shape of a cylindrical billet was formed in a press with the aim of analyzing the effect of different forging temperatures and required press load for optimal die filling. The component’s dimensions were later measured and compared to a reference piece. To ease the flow of material a lubricant was used between the billet and the die. This was demonstrated by compressing the billet with and without any lubricant. The performed experiments show that the lubricant reduces friction and makes it easier for the material to flow into the die. Higher billet temperature than 450 °C is deemed unnecessary as it does not give any significant improvement in filling the die. The experiments also conclude that a press load of at least 280 tons is required for these conditions.

  • 50.
    Ekendahl, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Development and evaluation of new method to messure hydrogen content in molten steel at Scana Steel Björneborg AB2005Independent thesis Basic level (degree of Bachelor)Student thesis
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