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  • 51.
    Lindgren, Michael
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Wikström, Lars
    Roll forming of partially heated cold rolled stainless steel2009In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 209, no 7, p. 3117-3124Article in journal (Refereed)
    Abstract [en]

    Today you will find roll formed details in many different products, for example buildings, household appliances and vehicles. The industry, in order to save weight, tends to use more and more high strength steel. The disadvantage with these materials is that they can be difficult to form due to reduced ductility. A way to increase the ductility in the forming areas is by partially heat the steel. It is shown that partial heating substantially increases the ductility of high strength steel and make it possible to roll form large bend angles. When roll forming, the material will work hardening almost to the as-received condition in the outer and inner radius of the roll formed profile. Furthermore, the heating power decides the bend angle obtained. Finally, the mechanical properties after heating and roll forming are discussed.

  • 52. Malmberg, P.
    et al.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Eriksson, C.
    Nygren, H.
    Richter, K.
    Analysis of bone minerals by time-of-flight secondary ion mass spectrometry: a comparative study using monoatomic and cluster ions sources2007In: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, E-ISSN 1097-0231, Vol. 21, no 5, p. 745-749Article in journal (Refereed)
    Abstract [en]

    Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is an important tool for the analysis of bone minerals at implant surfaces. Most studies have been performed with monoatomic primary ion sources such as Ga+ with poor secondary molecular ion production efficiency and only elemental distributions and minor fragments of bone minerals have been reported. By using cluster ion sources, such as Au and Bi, identification of larger hydroxyapatite species at m/z 485, 541, 597 and 653, identified as Ca5P3O12, Ca6P3O13, Ca7P3O14 and Ca8P3O15, respectively, became possible. The ions appear to be fragments of the hydroxyapatite unit cell Ca10(PO4)6(OH)2. Each ion in the series is separated by 55.9 m/z units, corresponding to CaO, and this separation might reflect the columnar nature of the unit cell. Copyright © 2007 John Wiley & Sons, Ltd.

  • 53. Olofsson, J.
    et al.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jacobson, S.
    Tribofilm formation of lightly loaded self mated alumina contacts2012In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 289, p. 39-45Article in journal (Refereed)
    Abstract [en]

    A tribofilm is formed on alumina surfaces that have been slid against alumina surfaces. The tribofilm is formed by alumina wear particles that have been ground, agglomerated and tribosintered to a film. The tribofilm smoothens out the surface topography and fills up cavities. Tribofilms on alumina surfaces have been investigated with respect to surface appearance, hardness and chemical composition. Surface preparation and surrounding humidity have shown to affect the character and lateral distribution of the tribofilm. The tribofilm that was formed in humid air was softer than the tribofilm formed in dry air. XPS analysis revealed the chemical shift of the Al 2p peak did not differ between the tribofilms that was formed in different humidity, nor the unworn reference surface, finding that no hydroxide was found on the alumina surfaces. Also, no tribochemical changes could be detected by ToF-SIMS analysis. (C) 2012 Elsevier B.V. All rights reserved.

  • 54.
    Olovsjö, S
    et al.
    Atlas Copco.
    Johanson, R
    Atlas Copco.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    On the understanding of cemented carbide degradation in rock drilling: the importance of metallographic sample preparation2012In: Proceedings of Euro PM 2012 Congress & Exhibition Vol. 2, 2012Conference paper (Refereed)
  • 55.
    Olovsjö, S
    et al.
    Atlas Copco.
    Johanson, R
    Atlas Copco.
    Falsafi, M
    Atlas Copco.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Surface failure and wear of cemented carbide rock drill buttons: the importance of sample preparation and optimized microscopy settings2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 302, no 1-2, p. 1546-1554Article in journal (Refereed)
    Abstract [en]

    The combination of suitable mechanical properties and wear resistance makes cemented carbide one of the most interesting engineering composite materials for tribological applications, such as in rock drilling. Despite the fact that cemented carbide buttons have been used in rock drilling applications for a long time the detailed understanding of the prevailing wear mechanisms is far from complete and wear and breakage of rock drill buttons are still one of the lifetime-limiting factors for rock drill bits. Consequently, further research in this area, including detailed characterization of worn drill button surfaces and sub-surface regions, is needed in order to support the future development of new cemented carbide grades with improved failure and wear resistance. In the present paper, high resolution scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Auger electron spectroscopy (AES) have been used to characterize the wear and failure mechanisms of worn drill buttons and samples exposed to well controlled impact and scratch tests performed in the laboratory. The most important mechanisms of surface failure and wear were found to be severe plastic deformation, cracking, crushing of individual WC grains and mechanical/tribochemical degradation of the Co binder phase including Co depletion. Fracture cross-sectioning under tensile stress-state was found to be the best method for achieving large and reliable sub-surface cross-sections within a short time and to a low cost. The importance of optimized microscopy and spectroscopy settings for enhanced surface sensitivity for the examination of small-scale tribological phenomena is illuminated and discussed.

  • 56.
    Olsson, Mikael
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Friction characteristics and material transfer tendency in metal powder compaction2011In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 271, no 9-10, p. 1903-1908Article in journal (Refereed)
    Abstract [en]

    The friction characteristics and material transfer tendency between metal powder and die tool material in metal powder compaction play an important role in the production of near-net-shape components of high density. A natural step to further increase the green density and simplify the sintering process is to reduce the amount of internal lubricant in the powder since the volume fraction of an organic lubricant will result in a significant contribution to the resulting porosity. However, this will significantly increase the adhesive contact and thus the friction between the die and the powder/green body during the powder compaction process. As a result, the compaction and ejection forces as well as the wear rate of the die and punch surfaces will increase. Consequently, improved knowledge concerning the friction mechanisms prevailing at the metal powder/die tool material interface is needed. The present paper will present data regarding the influence of type of tool and coating material on the friction characteristics and material transfer tendency during simulated powder compaction of a water atomized plain iron powder under no or starved lubrication conditions using two different laboratory tribo tests. Tool materials investigated include ingot cast tool steel, powder metallurgy (PM) tool steel and TiAlN and DLC-type PVD coatings. Post-test characterization using scanning electron microscopy and energy dispersive X-ray spectroscopy was used to analyse the tribo surfaces and especially the tendency to material transfer and tribo film formation. The results show that the material transfer tendency is mainly controlled by strong adhesive metal–metal contacts and that a PVD coating showing intrinsic low-friction properties and a smooth surface topography may significantly reduce the interaction between the mating surfaces promoting a stable friction and a low material transfer tendency.

  • 57.
    Olsson, Mikael
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Malmros, M.
    Bexell, Ulf
    Wiklund, U.
    Assessing the mechanical and electrical properties of aluminium oxid on aluminium using nanoindentation and nonoscratching2011In: Proccedings of the 18th International Conference on Wear of Materials, Philadelphia, USA, 2011Conference paper (Other academic)
  • 58.
    Persson, Tomas
    et al.
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Riedel, Jochen
    Berghel, Jonas
    Karlstads Universitet.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Win, Kaung Myat
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Emissions and deposit properties from combustion of wood pellet with magnesium additives2013In: Journal of Fuel Chemistry and Technology, ISSN 1872-5813, Vol. 41, no 5, p. 530-539Article in journal (Refereed)
    Abstract [en]

    This work studies the amount of gaseous and particleemissions and deposits on heat exchanger surfaces in a boiler fired withcommercially available pellets and with pellets primed with magnesium oxide andmagnesium hydroxide. The combustion experiments were performed on a residentialboiler of 20 kW. Substrates placed in the heat exchanger was analysed withSEM-EDX-mapping to evaluate the chemical composition of the deposits. Theresults show that particle emissions (PM 2.5) using the additives increased byabout 50% and the mass of the deposits in the flue gas heat exchanger (excludingloose fly ash) increased by about 25% compared to the combustion of pelletswithout additives. The amount of additives was found to be eight times higherthan the amount of the main alkali metals potassium (K) and sodium (Na) whichleads to the assumption that the additives were overdosed and therefore causedthe problems reported. The SEM analysis of the substrates placed in the fluegas heat exchanger indicate that the deposits of sodium (Na), potassium (K),chlorine (Cl) and sulphur (S) decrease using the additives. If this was due tothe expected chemical reactions or due to the loose fly ash covering thesubstrates after the test, could not be determined in this study.

  • 59. Prosek, T
    et al.
    Nazarov, A
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Thierry, D
    Serak, J
    Corrosion mechanism of model zinc–magnesium alloys in atmospheric conditions2008In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 50, no 8, p. 2216-2231Article in journal (Refereed)
    Abstract [en]

    Recently, superior corrosion properties of zinc coatings alloyed with magnesium have been reported. Corrosion behaviour of model zinc–magnesium alloys was studied to understand better the protective mechanism of magnesium in zinc. Alloys containing from 1 to 32 wt.% magnesium, pure zinc, and pure magnesium were contaminated with sodium chloride and exposed to humid air for 28 days. Composition of corrosion products was analyzed using infrared spectroscopy (FTIR), ion chromatography (IC), and Auger electron spectroscopy (AES). The exposure tests were completed with scanning Kelvin probe (SKP) and electrochemical measurements. Weight loss of ZnMg alloys with 1–16 wt.% magnesium was lower than that of pure zinc. Up to 10-fold drop in weight loss was found for materials with 4–8 wt.% Mg in the structure. The improved corrosion stability of ZnMg alloys was connected to the presence of an Mg-based film adjacent to the metal surface. It ensured stable passivity in chloride environment and limited the efficiency of oxygen reduction.

  • 60. Prosek, T.
    et al.
    Thierry, D.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Effects of chloride-to-chromate ratio on the protective action of zinc surface films under atmospheric weathering conditions2007In: Corrosion, ISSN 0010-9312, E-ISSN 1938-159X, Vol. 63, no 3, p. 258-267Article in journal (Refereed)
    Abstract [en]

    The formation and the corrosion protection of newly formed chromium-rich layers on bare zinc surfaces were studied to model the conditions in defected areas of both organic and conversion chromate coatings that are in contact with water environments contaminated with different amounts of chloride ions. Composition of the layers was idenified with Fourier transformed infrared spectroscopy (FTIR), x-ray absorption near-edge structure (XANES), and secondary ion mass spectroscopy (SIMS). The presence of chloride in the range from 0.06 mM to 1, 000 mM in the chromate treating solution had almost no effect on the amount of chromate adsorbed on zinc. Three independent techniques showed that a more than 4-order increase in chloride concentration results in the drop of the chromate content in the surface film only by 20% to 25%. Cr(VI)-to-total Cr surface ratio was close to 0.3 and constant under present experimental conditions. More chromium was detected in the outer region of the film, whereas chloride accumulated in the inner region. As a result of the linear increase of the surface chloride concentration with the chloride concentration in the chromate treating solution, the chloride-to-chromate surface molar ratio increased sharply. The rate of reduction of Cr(VI) to Cr(III) and the corrosion rate of zinc exposed to atmospheric weathering conditions increased significantly with the chloride-to-chromate ratio. The chromate coatings showed good stability and a high level of corrosion protection, up to the ratio of approximately 2. It represented a threshold value below which relatively low rates of the chromate reduction and zinc corrosion were observed, since the significant part of the chloride ions was inactivated in the first hours of exposure by the formation of insoluble corrosion products. A negative effect of the increasing chloride-to-chromate surface molar ratio on corrosion can be seen in the increasing ability to reduce oxygen on the zinc surface measured by the scanning Kelvin probe (SKP) technique. Inhibition of the cathodic reaction by chromate was less effective at higher ratios.

  • 61.
    Prosek, Tomas
    et al.
    Institut de la Corrosion / French Corrosion Institute.
    Nazarov, Andrej
    Institut de la Corrosion / French Corrosion Institute.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Thierry, Dominique
    Institut de la Corrosion / French Corrosion Institute.
    Serak, Jan
    Dept. of Metals and Corrosion Engineering, Institute of Chemical Technology, Praha, Czech Republic.
    Corrosion properties of model zinc-magnesium alloys2007In: GALVATECH 2007, 2007Conference paper (Other academic)
    Abstract [en]

    Recently, superior corrosion properties of novel zinc coatings alloyed with magnesium have been reported.The protection mechanism of magnesium in the coatings was studied on model zinc-magnesium alloys containing from1 to 32 wt. % Mg prepared by casting. Their chemical and phase composition was determined. The samples werecontaminated with NaCl and exposed to wet air. Weight loss was evaluated after 28 days of exposure. The compositionof corrosion products was analyzed using different techniques. The exposure tests were completed with scanning Kelvinprobe measurements. Alloying of zinc with small quantities of magnesium significantly decreased the weight lossof zinc-magnesium alloys. The effect was strongest at 4–8 wt. % Mg in the structure. Weight loss of these alloys was upto 10 times lower than that of zinc. This was found to be connected dominantly to the efficiency of the oxygenreduction, which was significantly limited on the surface of ZnMg phases covered with magnesium-based oxide layers.

  • 62. Rehnlund, D.
    et al.
    Lindgren, F.
    Böhme, S.
    Nordh, T.
    Zou, Y.
    Pettersson, J.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Boman, M.
    Edström, K.
    Nyholm, L.
    Lithium trapping in alloy forming electrodes and current collectors for lithium based batteries2017In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 10, no 6, p. 1350-1357Article in journal (Refereed)
    Abstract [en]

    Significant capacity losses are generally seen for batteries containing high-capacity lithium alloy forming anode materials such as silicon, tin and aluminium. These losses are generally ascribed to a combination of volume expansion effects and irreversible electrolyte reduction reactions. Here, it is shown, based on e.g. elemental analyses of cycled electrodes, that the capacity losses for tin nanorod and silicon composite electrodes in fact involve diffusion controlled trapping of lithium in the electrodes. While an analogous effect is also demonstrated for copper, nickel and titanium current collectors, boron-doped diamond is shown to function as an effective lithium diffusion barrier. The present findings indicate that the durability of lithium based batteries can be improved significantly via proper electrode design or regeneration of the used electrodes. © The Royal Society of Chemistry 2017.

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  • 63.
    Rhenlund, David
    et al.
    Uppsala Universitet.
    Lindgren, Fredrik
    Uppsala Universitet.
    Böhme, Solveig
    Uppsala Universitet.
    Nordh, Tim
    Uppsala Universitet.
    Zou, Yiming
    Uppsala Universitet.
    Pettersson, Jean
    Uppsala Universitet.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Boman, Mats
    Uppsala Universitet.
    Edström, Kristina
    Uppsala Universitet.
    Leif, Nyholm
    Uppsala Universitet.
    Improved Cycling Stability of Conversion and Alloying Anodes through the use of Nanomaterials2016Conference paper (Refereed)
  • 64. Riedel, Jochen
    et al.
    Persson, Tomas
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Berghel, Jonas
    Win, Kaung Myat
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Eldningsresultat för pellets med tillsats av magnesium2011Report (Other academic)
    Abstract [sv]

    Vid förbränning av biobränslen såsom träpellets bildas partiklar som orsakar avsättningar på ytor i pannans konvektionsparti. Det som leder till försämrad effektivitet och kräver sotning. Dessutom sker utsläpp av partiklar till uteluften som kan ge hälsoeffekter. Vid förbränning kan alkalimetaller, som till exempel kalium, frigöras från bränslet och de kan bilda klibbiga avsättningar tillsammans med klor, svavel eller kisel, som i sin tur samlar in mer partiklar och det bygger på avsättningar i konvektionspartiet. Det förväntas att magnesi-um reagerar (huvudsakligen med klor, svavel och kisel) så att sammansättningar med högre smältpunkter erhålls, vilket kan minska avsättningar i konvektionspartiet. Karlstads Universitet har producerat tre olika typer av träpellets; en referenspellet utan tillsat-ser, en pellet med magnesiumoxid (MgO) och en pellet med magnesiumhydroxid (Mg(OH)2). Kortare eldningsprov med de olika bränslena har genomförts i en 20 kW pelletspanna och uppkomna avsättningar i konvektionspartiet och emissioner har registreras. Avsättningarna i konvektionspartiet kvantifierades med en gravimetrisk metod och analyserades med SEM, vilket gör det möjligt att se vilka grundämnen som förekommer i avsättningarna. Gasformiga emissioner som CO, NO och TOC registrerades liksom partikelutsläpp. Motsvarande försök gjordes också med en kommersiellt tillverkad pellet. Tillsats av MgO och Mg(OH)2 ökade mängden flygaska och partikelutsläpp (PM 2,5). Massan av fasta beläggningar i konvektionspartiet ökade också jämfört med referenspellets utan dessa tillsatser. Dessutom bildades stora mängder flygaska i fallen med magnesiumtillsats. Att tillsatserna bildade flygaska kan förklaras av den normalt mycket låga askhalten i träpel-lets och därmed är också halten av alkalimetaller låg jämfört med pellets som tillverkas av spannmål. Magnesiumtillsatsen syftar till att reagera med alkalimetaller och bilda föreningar med så hög smältpunkt att de inte fastnar i pannans konvektionsparti. Troligen är magnesium-tillsatsen för hög jämfört med mängden alkali i pelletsen. Från SEM-analysen kan man se att mängden kalium minskar med magnesiumtillsatserna och det verkar som att principen fungerar. Dock hamnade stora mängder flygaska med hög andel magnesium i konvektionspartiet (lös flygaska har avlägsnats före den gravimetriska mätning-en och före SEM-analysen av substraten). Detta kan ha förhindrat substraten från att få högre andel fasta avsättningar från bland annat kalium och klor under denna korta mätperiod som genomfördes. Det kan dock inte uteslutas att de minskade avsättningarna av kalium och klor berodde på just tillsatsen av magnesium.

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  • 65.
    Saketi, Sara
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology. Uppsala University.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology. Uppsala University.
    Wear mechanism of cemented carbide cutting tool in the turning of 316L stainless steel2018Conference paper (Refereed)
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  • 66.
    Saketi, Sara
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Östby, Jonas
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    On the diffusion wear of cemented carbide in the turning of 316L austenitic stainless steel2019In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 430-431, p. 202-213Article in journal (Refereed)
    Abstract [en]

    The present study focuses on the wear and wear mechanisms of three different cemented carbide grades during orthogonal turning of 316L austenitic stainless steel at different cutting speeds. The influence of WC grain size and cutting speed on the resulting crater and flank wear was evaluated by optical surface profilometry and scanning electron microscopy (SEM). The mechanisms behind the crater and flank wear were characterized on the sub-micrometer scale using high resolution SEM, energy dispersive X-ray spectroscopy (EDS), Auger electron spectroscopy (AES) and time of flight secondary ion mass spectrometry (ToF-SIMS) of the worn cutting inserts and the produced chips.

    The results show that the wear rate of cemented carbide drastically increases with increasing cutting speed and that the wear is dependent on the WC grain size; i.e. the crater wear decreases with increasing WC grain size while the flank wear increases with increasing WC grain size. High resolution SEM, AES and ToF-SIMS analysis of the worn cemented carbide within the crater and flank wear regions reveal that the degradation of cemented carbide at higher cutting speeds is mainly controlled by diffusion wear of the WC-phase. This is confirmed by ToF-SIMS analysis of the back-side of stainless steel chips which reveals the presence of a 10 nm thin W-containing oxide film. The results are discussed and interpreted in the light of the conditions prevailing at the tool-chip interface.

  • 67.
    Saketi, Sara
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology. Uppsala universitet.
    Östby, Jonas
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    A methodology to systematically investigate the diffusion degradation of cemented carbide during machining2019In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 14, article id 2271Article in journal (Refereed)
    Abstract [en]

    Using Ti6Al4V as a work material, a methodology to systematically investigate the diffusion degradation of cemented carbide during machining is proposed. The methodology includes surface characterization of as-tested worn inserts, wet etched worn inserts, metallographic cross-sectioned worn inserts as well as the back-side of the produced chips. Characterization techniques used include scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Auger electron spectroscopy (AES) and time of flight secondary ion mass spectroscopy (ToF-SIMS).

    The results show that the characterization of wet etched worn inserts give quick and useful information regarding the diffusion degradation of cemented carbide, in the present work the formation of a fine crystalline W layer (carbon depleted WC layer) at the tool / work material interface. The present study also illuminates the potential of AES analysis when it comes to analyzing the degradation of cemented carbide in contact with the work material during machining. The high surface sensitivity in combination with high lateral resolution makes it possible to analyze the worn cemented carbide surface on a sub-µm level. Especially AES sputter depth profiling, resulting in detailed information of variations in chemical composition across interfaces, is a powerful tool when it comes to understanding diffusion wear. Finally, the present work illustrates the importance of analyzing not only the worn tool but also the produced chips. An accurate characterization of the back-side of the chips will give important information regarding the wear mechanisms taking place at the tool rake face / chip interface. Surface analysis techniques such as AES and ToF-SIMS are well suited for this type of surface characterization.

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  • 68.
    Saketi, Sara
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology. Uppsala universitet.
    Östby, Jonas
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology. Uppsala universitet.
    Wear behaviour of two different cemented carbide grades in turning 316 L stainless steel2018In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 941, p. 2367-2372Article in journal (Refereed)
    Abstract [en]

    Cemented carbides are the most common cutting tools for machining various grades of steels. In this study, wear behavior of two different cemented carbide grades with roughly the same fraction of binder phase and carbide phase but different grain size, in turning austenitic stainless steel is investigated. Wear tests were carried out against 316L stainless steel at 180 and 250 m/mincutting speeds. The worn surface of cutting tool is characterized using high resolution scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Auger electron spectroscopy (AES) and 3D optical profiler.The wear of cemented carbide in turning stainless steel is controlled by both chemical and mechanical wear. Plastic deformation, grain fracture and chemical wear is observed on flank and rake face of the cutting insert. In the case of fine-grained, the WC grains has higher surface contact with the adhered material which promotes higher chemical reaction and degradation of WC grains, so chemical wear resistance of the composites is larger when WC grains are larger. The hardness of cemented carbide increase linearly by decreasing grain size, therefore mechanical wear resistance of the composites is larger when WC grains are smaller.

  • 69. Stanciu, V.
    et al.
    Wilhelmsson, O.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Adell, M.
    Sadowski, J.
    Kanski, J.
    Warnicke, P.
    Svedlindh, P.
    Influence of annealing parameters on the ferromagnetic properties of optimally passivated (Ga,Mn)As epilayers2005In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 72, no 12, article id 125324Article in journal (Refereed)
    Abstract [en]

    The influence of annealing parameters—temperature (Ta) and time (ta)—on the magnetic properties of As-capped (Ga,Mn)As epitaxial thin films has been investigated. The dependence of the transition temperature (TC) on ta marks out two regions. The TC peak behavior, characteristic of the first region, is more pronounced for thick samples, while for the second ("saturated") region the effect of ta is more pronounced for thin samples. A right choice of the passivation medium, growth conditions along with optimal annealing parameters routinely yield TC-values of ~150 K and above, regardless of the thickness of the epilayers

  • 70.
    Sveen, Susanne
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology. Linköpings Universitet.
    M’Sauobi, R
    Seco Tools.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    PCBN hard turning of ball bearing steel: Influence of PVD coating deposition on tool wear and surface finish/surface integrity of machined surfaceManuscript (preprint) (Other academic)
  • 71. Wikström, Lars
    et al.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Lindgren, Michael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Partial annealing of stainless steel before roll forming2007In: Stål 2007, 2007Conference paper (Other academic)
  • 72.
    Yvell, Karin
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Lindgren, Michael
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    A microstructural investigation of roll formed austenitic stainless steel2013In: Sheet metal 2013: Key engineering metals, 2013, Vol. 549, p. 364-371Conference paper (Refereed)
    Abstract [en]

    Due to high production rates and the possibility to form complex geometries roll forming has become an increasingly popular forming process for sheet metal. Increasing quantities of high strength steels are used today but can be difficult to form due to their low ductility. One way to partly overcome this problem is to heat the steel in the forming area thus locally increasing the ductility. In the present study partially heated cold rolled high strength AISI 301 type austenitic stainless steel was investigated using electron backscattered diffraction (EBSD), and the results were compared to microhardness measurements. The results show that partial heating will give an almost complete reverse martensite transformation, i.e. martensite (alpha') transforms to austenite (gamma), close to the surfaces and grain growth in the middle of the steel sheet. The extension of the heat affected zone can be determined using either microhardness or EBSD measurements. Both these measurements can be used to determine the position of the neutral layer after roll forming. The hardness measurement cannot distinguish between microstructural features but the results are in good agreement with the EBSD results for volume fraction of alpha'-martensite. A major advantage of using EBSD is the possibility to characterize and follow the microstructural development when heating and roll forming.

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