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  • 51. Habainy, J.
    et al.
    Lee, Y.
    Surreddi, Kumar Babu
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Prosvetov, A.
    Simon, P.
    Iyengar, S.
    Dai, Y.
    Tomut, M.
    Study of heavy ion beam induced damage in tungsten for high power target applications2019In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 439, p. 7-16Article in journal (Refereed)
    Abstract [en]

    The spallation material at ESS is pure tungsten, which is cooled by gaseous helium flow. To study the behaviour of tungsten under dynamic beam conditions at ESS, pure tungsten specimens have been irradiated at the M3-beamline of the UNILAC facility at GSI Helmholtz Centre for Heavy Ion Research. Tungsten specimens of two thicknesses, 26 μm and 3 mm, were exposed to pulsed uranium and gold ion beams for fluences up to 7.5 · 1013 ions·cm−2 at 4.8 MeV/nucleon. Nanoindentation tests were performed on the cross section of the irradiated 3 mm sample, and microhardness was measured on the top surface. The measured data are compared with the calculated damage values, and a correlation between the radiation induced damage and the observed mechanical property is presented. Thermal diffusivities of foil samples irradiated up to four different fluences were measured with a Laser Flash Apparatus (LFA). The observed changes in the mechanical and thermal properties of irradiated tungsten were used to estimate the changes of operational temperature and mechanical stresses in the ESS target material with the progress of radiation damage, using coupled thermal and mechanical simulations. From the pulsed beam induced dynamic oscillations of thin tungsten specimens, information on fatigue properties of tungsten under irradiation was drawn. In addition to pure tungsten, oxidised tungsten samples were irradiated. This is to investigate the stability of the adhesive oxide layer under pulsed beam conditions, which would be formed due to oxygen impurities in the helium cooling loop. The irradiated oxide scale was examined using Auger Electron Spectroscopy (AES) and Scanning Electron Microscopy (SEM). 

  • 52.
    Hall, Josefin
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Beglund, Tomas
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Influence of microstructure and hard phase content on the mechanisms of deformation and wear of HIP:ed Stellite® 190 composites2015Conference paper (Refereed)
  • 53.
    Hall, Josefin
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Fletcher, J. S.
    Canovic, S.
    Malmberg, Per
    Comparing depth profiling of oxide scale on SOFC interconnect-materials using ToF-SIMS with 69Ga+, Bi3+/Cs+ and C60+/C602+ as primary and sputter ions2015In: Materials at High Temperatures, ISSN 0960-3409, Vol. 32, no 1-2, p. 133-141Article in journal (Refereed)
    Abstract [en]

    Oxide scale cross-sections of CeO2 coated FeCr based solid oxide fuel cell interconnect materials were examined using secondary ion mass spectrometry (SIMS) depth profiling. A duplex spinel∶chromia scale was formed after 1 h at 850°C. Ti and ceria were observed between these layers. Additionally, minor concentrations of Mn, Si and Nb were observed at the oxide/metal interface. Furthermore, Al and Ti were concentrated primarily in the metal surface close to the oxide/metal interface. Secondary ion mass spectrometry sputter depth profiles using different ion sources; 69Ga+, Bi3+/Cs+ and C60+/C602+ were compared with TEM oxide scale cross-section and field emission gun–Auger electron spectroscopy depth profiling. Secondary ion mass spectrometry depth profiling with 69Ga+, Bi3+/Cs+ showed decreased secondary ion yields in the metallic matrix. This decrease could be avoided using oxygen flooding. The C60cluster ion depth profiles were less sensitive to type of matrix and gave the best correspondence to the TEM cross-section. However, the impact energy has to be high enough to avoid carbon deposition.

  • 54.
    Hall, Josefine
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Berglund, Tomas
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Influence of Microstructure and Hard Phase Content on the Mechanisms of Deformation and Wear of HIP:ed Stellite® 190 Composites2015In: Proceedings of 2015 European powder metallurgy congress, Euro PM 2015, Reims, France, 4-7 October 2015, 2015Conference paper (Refereed)
  • 55.
    Halldén, Helena
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Planhet efter skärande bearbetning av formatplåt – en jämförelse mellan laserskärning och gradsaxklippning2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In recent years, SSAB has had a growing quality problem regarding residual stresses in sheet metal. The problem means that unevenness arises in connection with the customer processing, mainly during laser cutting, although the company has delivered a seemingly flat material.

    SSAB currently has power shearing within the company as an evaluation method for determining the internal stresses in metal sheet after leveling in sheet cutting line 3. However, there is a big difference between power shearing and the process laser cutting, which usually is the customer´s actual process method. Consequently, results from evaluating the two operations can differ. For that reason power shearing is questioned as a test method of residual stresses.

    The thesis compares the two operations power shearings and laser cuttings impact on flatness of leveled sheet metal, and thereafter to evaluate power shearing as a test method of unevenness. The intention of the thesis is also to determine how different leveling parameters may affect the results of the comparison.

    The work was performed by three different production trials. The first trial was leveling and cutting sheet metal. Thereafter some of the sheets were cut in a laser cutting machine and the rest with a power shearing machine. The result was in both cases smaller plates. The unevenness of the plates was measured by hand and then the results were compiled in order to read the results and make relevant comparisons between the cutting methods.

    The results show that power shearing, as an evaluation method to predict unevenness after laser cutting, is not a good method. Poor set leveling parameters also increases the uncertainty of the valuation method. However, a combination of power shearing into two different versions of plates, can provide some information about the unevenness of a corresponding laser cut sheet leveled with the same leveling settings.

  • 56.
    Harfouche, Sara
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Dimensionsmätning av varma ämnen iLIMAB och undersökning avkrympfaktorer2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    At the rolling mill in Ovako, Hofors, bars are produced in different dimensions during a hot rolled procedure. After the last rollers, a dimension gauge LIMAB was installed. LIMAB measures the bars at high temperatures, around 900 oC.

    When the bars of different steel types cool down to room temperature, they shrink differently. Exactly how much they shrink is of interest to the customers who want specific dimensions of their products.

    Two types of steels with different carbon content have been analyzed in in this project. By comparing the bars hot dimension values from the dimension gauge with the cold measured values, a shrinkage factor can be calculated.

    Several types of shrinkage formulas were compiled and the result shows a lineup of all the

    evaluated formulas and how the shrinkage factors deviate from each other.

    The production of rings formula gives us the highest value on the shrinkage factor based on our calculations. The next highest values are from LIMAB AB and the lowest values are from the production of pipes.

    Currently, it is difficult to determine new shrinkage factor values because it requires more experiments and some capability measurements.

  • 57. Harlin, P.
    et al.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Starch consolidation of M3/2 high speed steel powder: Influence of microstructure on mechanical properties2007In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 50, no 3, p. 232-238Article in journal (Refereed)
    Abstract [en]

    The influence of microstructure on the mechanical properties of starch consolidated super solidus liquid phase sintered AISI type M3/2 high speed steel powder has been evaluated. Hardness measurements, Rockwell C indentation and scratch testing were used to evaluate the mechanical properties and light optical microscopy and scanning electron microscopy were used for post-test characterisation. The results show that it is possible to starch consolidate and sinter large particle size high speed steel powder to obtain microstructures with high mechanical strength. However, the results show a strong correlation between the as sintered microstructure and the resulting mechanical properties and illuminate the importance of having a dense and isotropic microstructure in order to meet engineering requirements in demanding applications. Consequently, the failure mechanisms observed during indentation and scratch testing can be related to residual pores, present in the low temperature sintered samples, and a coarse microstructure with eutectic carbides, present in the high temperature sintered samples. 

  • 58.
    Harlin, Peter
    et al.
    Sandvik Materials Technology.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Influence of surface topography of arc-deposited TiN and sputter-deposited WC/C coatings on the initial material transfer tendency and friction characteristics under dry sliding contact conditions2009In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 203, no 13, p. 1748-1755Article in journal (Refereed)
    Abstract [en]

    The influence of surface topography of PVD coatings on the initial material transfer tendency and friction characteristics in dry sliding contact conditions has been investigated. A modified scratch test was used to evaluate the material transfer tendency between ball bearing steel and two different PVD coatings, TiN and WC/C, under dry sliding contact conditions. Post test characterisation of the contact surfaces was performed using SEM/EDS and AES in order to map the initiation points and mechanisms for material transfer. The results show that the resulting topography of the PVD coated surfaces is strongly dependent on both the substrate material topography and the topography induced by the coating deposition process used. In sliding contact with a softer surface the coating topography results in a significant material pick-up tendency of the PVD coated surfaces. The material pick-up is mainly controlled by the abrasive action of hard coating asperities and as a result a polishing post treatment of the as-deposited PVD coatings significantly reduces the material pick-up tendency. For the WC/C coating, showing intrinsic low friction properties, the post treatment inhibits the material pick-up and results in a low and stable friction coefficient (mu similar to 0.1). For the TiN coating, that lacks intrinsic low friction properties, the post treatment reduces the material pick-up tendency but has no significant influence on the friction characteristics. This is mainly due to the presence of metallic Ti originating from the macroparticles on the TiN coating which results in a reactive surface that promotes a strong adhesion between the mating surfaces.

  • 59. Hatami, S.
    et al.
    Armada, S.
    Laurent, A.
    Nyborg, L.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Tribological properties of powder metallurgical tool steels used in powder compaction pressing dies2011In: Lubrication Science, ISSN 0954-0075, E-ISSN 1557-6833, Vol. 23, no 3, p. 139-152Article in journal (Refereed)
    Abstract [en]

    The tribological properties of two powder metallurgical (PM) tool steels, high and low nitrogen containing, are investigated by means of three different wear tests: ball-on-disc, rubber wheel and scratch test. The ball-on-disc tests showed two distinct friction curves corresponding to each material. In order to simulate the tribosystem existing in metal powder compaction dies, the rubber wheel and the scratch test were modified. The rubber wheel test was performed using ferrous powder instead of sand, and scratch testing was carried out by sliding a powder compact over the tool steels. The scratch tests indicated a higher steady-state coefficient of friction for the low nitrogen containing PM steel as compared with the high nitrogen containing alloy. Additionally, the results from the rubber wheel tests were in agreement with industrial experiences, showing the low nitrogen containing tool steel to suffer from severe galling.

  • 60.
    Hedman, Fanny
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Inverkan av processparametrar i varmvalsverket på planhet efter formatklippning2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    After the hot rolling mill the coils are sent either untreated or pickled to be leveled and cut in one off the different cut to length lines in SSAB Borlänge.

    The results on the flatness after leveling and cutting in the cut to length line 4 shifts even though the coils are from the same steel type. Many factors could affect the flatness and this thesis examines if the geometry on the coil after the hot rolling mill has any impact on the flatness after the cut to length line 4. The studies have been limited to a few steel types and dimensions.

    In order to find a connection between the hot rolling mill and the cut to length line were information on historical coils gathered from data bases that are connected to the different production lines.

    The connections that were found were that with a lower crown on the coils the flatness results are better. The wedge on good and defect coils varies and a thicker drive side gives a better flatness result than a thicker free side gives. Even the shape of the cross profile is affecting the flatness results.

    To verify these connections two production experiments were done, one where some coils were rolled and cut to length without any changes on the parameters and one where some parameters were changed before the coils was rolled and cut to length. The production experiments proved the connections because the good coils had the lowest crown.

  • 61.
    Heinrich, Jannica
    et al.
    Tribomaterials Group, The Ångström Laboratory, Uppsala University.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology. Tribomaterials Group, The Ångstrom Laboratory, Uppsala University.
    Jenei, Istvan Zoltan
    Instrumentation Physics, Stockholm University.
    Jacobson, Staffan
    Tribomaterials Group, The Ångström Laboratory, Uppsala University.
    Transfer of titanium in sliding contacts: new discoveries and insights revealed by in situ studies in the SEM2014In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 315, no 1-2, p. 87-94Article in journal (Refereed)
    Abstract [en]

    Titanium and its alloys generally display poor tribological properties in sliding contacts due to their high chemical activity and strong adhesion to the counter surface. The strong adhesion causes a high tendency to transfer and ultimately galling or build-up edge formation, resulting in severe surface damage. As a result, forming and machining of titanium and its alloys are generally associated with significant problems such as high friction, rapid tool wear and poor surface finish of the formed/machined surface.

    In the present study, in situ tests in a scanning electron microscope have been performed to increase the understanding of the mechanisms controlling the initial transfer of titanium (Grade 2) in sliding contact with tool surfaces. Tool materials included cover cold work tool steel, cemented carbide, CVD deposited Al2O3and PVD deposited DLC. In these tests, a relatively sharp tip, representing the titanium work material, slides against a flat surface, representing the tool. The contact conditions result in plastic deformation of the work material against the tool surface, thereby simulating forming or machining. The limited and well-defined contact, along with the possibility to study the sliding in the SEM, makes it possible to correlate local surface variations to transfer of work material and frictional response. Post-test characterization of the contact surfaces was performed by high-resolution SEM, TEM, EDS and EELS.

    The initial friction was low and stable against all tested materials, but then gradually escalated against all surfaces except the DLC. The friction escalation was associated to increasing levels of transfer, while the DLC stayed virtually free from transfer. From these very initial sliding tests DLC is a promising tool coating in forming and machining of titanium.

  • 62.
    Heinrichs, J
    et al.
    Uppsala Universitet.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jacobson, S
    Uppsala Universitet.
    Influence of tool steel microstructure on initial material transfer in metal forming: in situ studies in the SEM2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 302, no 1-2, p. 1249-1256Article in journal (Refereed)
    Abstract [en]

    Metal forming constitutes a group of industrially important processes to form metallic components to net shape. When forming aluminium and other materials that tend to stick to the tools, problems associated with material transfer, e.g. galling, may occur. In a previous study by the present authors, in situ observations of aluminium transfer during sliding contact in the SEM revealed that the surface topography and chemical composition of the tool steel counter surface have a strong impact on the initial material transfer tendency. Even if carefully polished to a very smooth surface (Ra<50 nm), transfer of aluminium was found to immediately take place on a very fine scale and preferentially to the surface irregularities presented by the slightly protruding M(C,N) particles (height 15 nm) in the tool steel. In contrast, the less protruding M6C carbides, as well as the martensitic steel matrix exhibited very little initial transfer. The mechanism behind the preferential pick-up tendency displayed by the M(C,N) particles was not fully understood and it was not possible to determine if the decisive mechanism operates on the microstructural scale, the nanoroughness scale or the chemical bonding scale. In the present study, these mechanisms have been further investigated and analysed by comparing the very initial stages of material transfer onto different types of tool steels in sliding contact with aluminium in the SEM. The tool steels investigated cover conventional ingot cast and powder metallurgy steel grades, selected to possess a range of different types, amounts and sizes of hard phase particles, including MC, M(C,N), M7C3 and M6C. The transfer mechanisms are investigated using high resolution SEM, and the differences between the different microstructures and carbide types are carefully analysed. The implications for real metal forming are discussed.

  • 63.
    Heinrichs, J
    et al.
    Uppsala Universitet.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jacobson, S
    Uppsala Universitet.
    Initial deformation and wear of cemented carbides for rock drilling as evaluated by a sliding wear test2015In: Proceedings of International Tribology Conference 2015, 2015Conference paper (Refereed)
  • 64. Heinrichs, J.
    et al.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jacobson, S.
    Initial deformation and wear of cemented carbides in rock drilling as examined by a sliding wear test2017In: International journal of refractory metals & hard materials, ISSN 0958-0611, E-ISSN 2213-3917, Vol. 64, p. 7-13Article in journal (Refereed)
    Abstract [en]

    Due to a combination of high hardness and toughness, resulting in excellent wear resistance, cemented carbides are commonly used as the rock crushing component in rock drilling. The present paper presents a unique study where the very initial stages of deformation and wear of cemented carbide in sliding contact with rock are followed in small incremental steps. After each step, a pre-determined area within the wear mark is characterized using high resolution SEM and EDS. This facilitates analysis of the gradual deformation, material transfer, degradation and wear. The deterioration mechanisms found in this sliding test are similar to those observed in actual rock drilling. Cemented carbide grades with different microstructures show significant differences, where a higher amount of Co and a larger WC grain size both are associated to more wear. 

  • 65.
    Heinrichs, J.
    et al.
    Uppsala universitet.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology. Uppsala universitet.
    Jacobson, S.
    Uppsala universitet.
    Surface degradation of cemented carbides in scratching contact with granite and diamond: the roles of microstructure and composition2015In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 342, p. 210-221Article in journal (Refereed)
    Abstract [en]

    Cemented carbides are composite materials comprising metal carbide grains in a more ductile metallic binder. This microstructure results in a combination of high hardness and toughness, making them commonly used as rock crushing parts in rock drilling, where they usually show wear on a very fine scale. The hardness and toughness can ultimately be tuned for the application by adjusting the carbide grain size, binder fraction and composition.In the present investigation, the initial micro-scale deformation and wear of polished cemented carbide surfaces is studied by micro scratching with diamond and granite styli, and also by instrumented micro and nanoindentation. The deformation and wear is evaluated on the sub-micrometer scale using high resolution FEG-SEM and FIB cross sectioning. The selected microstructures include besides four cemented carbide grades that are commonly used in rock drilling also binderless and Ni containing grades. This wider range of cemented carbides is used to gain fundamental insights into the relations between microstructure and micro-scale deformation and wear. The results are discussed with respect to their significance for wear of cemented carbides in rock drilling operations.

  • 66.
    Heinrichs, J
    et al.
    Uppsala Universitet.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jenei, I. Z,
    Stockholms Universitet.
    Jacobson, S
    Uppsala Universitet.
    Transfer of titanium in sliding contacts – New discoveries and insights revealed by in situ studies in the SEM2013In: Proceedings of World Tribology Congress 2013, Torino, Italy, September 8 – 13, 2013, 2013Conference paper (Refereed)
  • 67. Heinrichs, J.
    et al.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology. Uppsala University.
    Yvell, Karin
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jacobson, S.
    On the deformation mechanisms of cemented carbide in rock drilling: Fundamental studies involving sliding contact against a rock crystal tip2018In: International journal of refractory metals & hard materials, ISSN 0958-0611, E-ISSN 2213-3917, Vol. 77, p. 141-151Article in journal (Refereed)
    Abstract [en]

    Cemented carbide is a composite material, most commonly consisting of tungsten carbide grains in a metallic matrix of cobalt. The combination of a hard ceramic phase in a ductile metallic matrix combines high hardness and ability to withstand plastic deformation with toughness to avoid cracking and fracturing. Since these properties are very important in rock drilling, cemented carbides are frequently used in such applications. In earlier work, it was found that granite in sliding contact with considerably harder cemented carbides not only results in plastic deformation of the cemented carbide composite, but also in plastic deformation of some of the individual WC grains. The latter observation is remarkable, since even the two hardest granite constituents (quartz and feldspar) are significantly softer than the WC grains. This tendency to plastic deformation of the WC grains was found to increase with increasing WC grain size. The present investigation aims to increase the understanding of plastic deformation of cemented carbides in general, and the individual WC grains in particular, in a situation representative for the rock drilling application. The emphasis is put on explaining the seemingly paradoxical fact that a nominally softer counter material is able to plastically deform a harder constituent in a composite material. The experimental work is based on a scratch test set-up, where a rock crystal tip slides against a fine polished cemented carbide surface under well-controlled contact conditions. The deformation and wear mechanisms of the cemented carbide are evaluated on the sub-micrometer scale; using high resolution FEG-SEM, EDS, EBSD, BIB and FIB cross-sectioning. The size of the Co-pockets, together with the shape and size of WC grains, turned out to be decisive factors in determining the degree of carbide deformation. The results are discussed with respect to their industrial importance, including rock drilling.

  • 68.
    Heinrichs, J
    et al.
    Uppsala Universitet.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Yvell, Karin
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jacobson, S
    Uppsala Universitet.
    Soft rock scratches hard cemented carbide2015In: Proceedings of Wear of Materials, 2015Conference paper (Refereed)
  • 69.
    Heinrichs, J
    et al.
    Uppsala Universitet.
    Yvell, Karin
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology. Uppsala universitet.
    Jacobson, S
    Uppsala Universitet.
    Influence of hardness and microstructure on the mechanisms of deformation and wear of cemented carbides for rock drilling2014In: Proceedings of 16th Nordic Conference on Tribology, Aarhus, Denmark, June 10-13, 2014, 2014Conference paper (Refereed)
  • 70.
    Heinrichs, Jannica
    et al.
    Tribomaterials group, The Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Gerth, Julia
    Tribomaterials group, The Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Thersleff, Thomas
    Applied Materials Science, The Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Larsson, Mats
    Primateria AB, Uppsala, Sweden.
    Wiklund, Urban
    Tribomaterials group, The Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Influence of sliding speed on modes of material transfer as steel slides against PVD tool coatings2013In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 58, p. 55-64Article in journal (Refereed)
    Abstract [en]

    An intermittent sliding test was used in order to study the formation and build- up of tribofilms during intermittent sliding of PVD coated HSS against case hardening steel (20NiCrMo2). Two cutting tool coatings were tested, TiN and AlCrN, and the influence of sliding speed was evaluated. With moderate speed,  two tribofilms were formed separately, one consisting of Mn, Si, Al and O on an intermediate layer  of Fe and one consisting of Fe, Mn, Cr and O on an intermediate layer of Cr and Mn. At low sliding speeds an uneven transfer of steel occured while high sliding speeds resulted in thermal softening of the substrate leading to coating failure. AlCrN provided better substrate protection at high speeds than TiN did.

  • 71. Heinrichs, Jannica
    et al.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology. Uppsala universitet.
    Almqvist, Bjarne
    Jacobson, Staffan
    Initial surface failure and wear of cemented carbides in sliding contact with different rock types2018In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 408-409, p. 43-55Article in journal (Refereed)
    Abstract [en]

    The initial wear, deformation and degradation of cemented carbide in contact with different rock types are studied using a crossed cylinder sliding test. The sliding distance is limited to centimetres at a time, interrupted by successive SEM analysis. This allows for careful studies of the gradually changing microstructure of the cemented carbide during the test. Five different rock types are included; granite, metal sulphide ore, mica schist, quartzite and marble. All rock types are very different in microstructure, composition and properties. The cemented carbide grade used for the evaluation contains 6 wt% Co and fine (~ 1 µm) WC grains, a grade commonly used in rock drilling. The results show that the cemented carbide microstructure becomes altered already during the very first contact with rock. The initial wear rate and wear character is highly influenced by the rock type. The initial wear of the cemented carbide is highest against quartzite and lowest against marble.

  • 72.
    Heinrichs, Jannica
    et al.
    Uppsala University.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jacobson, Staffan
    Uppsala University.
    Initial wear of cemented carbides in sliding contact with different rock types2016In: Proceedings of the 17th Nordic Symposium on Tribology - Nordtrib 2016, 2016Conference paper (Refereed)
  • 73.
    Herrdin, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Modell för att utvärdera spänningar vid reducervalsning2005Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [sv]

    Ovako Steel AB i Hofors tillverkar varmvalsade rör. Ett av de sista stegen i tillverkningsprocessen är en konventionell valsning i ett antal valspar kallad reducervalsning. De valsade rören uppvisar ibland en ojämn väggtjocklek längs rörlängden på grund av att det uppstår drag- och tryckspänningar i rören mellan valsparen. Syftet med examensarbetet är att öka kunskapen om dessa spänningars inverkan på det färdiga röret samt ge förslag på hur processen kan förbättras. I examensarbetet har undersökts vilka parametrar som påverkar spänningarna i valsningsprocessen. Detta har utförts genom att skapa en teoretisk modell för valsning utan drag- och tryckspänningar som sedan jämförs med uppmätta data från sju provade rör med olika mått och materialtyper. Försök har även utförts genom att variera valsmotorernas hastigheter för att inducera drag- och tryckspänningar i rören. Resultatet visar att spänningarna påverkas av rörens reduktion, valsarnas hastighetsökning, materialtyp och antal valsar i valsserien. Valsarnas styrning medför att spänningsfri valsning endast kan erhållas genom att förändra rörets reduktion i valsarna. Resultaten visar även att valsarnas motorhastighet kan användas för att motverka de spänningar som uppstår under valsningsprocessen.

  • 74. Hooshyar, H.
    et al.
    Jonsson, T.
    Hall, Josefine
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Svensson, J. -E
    Johansson, L. G.
    Liske, J.
    The effect of H2 and H2O on the oxidation of 304L-stainless steel at 600 °C: general behaviour (part I)2016In: Oxidation of Metals, ISSN 0030-770X, E-ISSN 1573-4889, Vol. 85, no 3-4, p. 321-342Article in journal (Refereed)
    Abstract [en]

    The effect of p(H2O) and p(H2) on the oxidation of 304L stainless steel at 600 °C has been investigated in the present study. The samples were analysed by means of X-ray diffraction, Auger spectroscopy, and scanning electron microscopy equipped with energy dispersive spectroscopy. The results showed that at fixed p(H2), the corrosion rate increased considerably with increasing p(H2O). At fixed p(H2O), the corrosion rate decreased slightly with increasing p(H2). Duplex oxide scales formed during the exposure in all environments. The outer and inner layer consisted of Fe3O4 and (Fe, Cr)3O4, respectively. The latter was mainly in the form of internal oxidation. The Cr-rich oxide formation was observed at the initial oxidation process before oxide breakdown. The Auger analysis also suggested the presence of Cr-rich oxide layer just after the breakaway oxidation. The results indicated that the rate-determining step in the corrosion attack is surface controlled or diffusion controlled through an oxide layer with fixed thickness over time.

  • 75.
    Huang, Shuo
    et al.
    Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden..
    Vida, Adam
    Wigner Res Ctr Phys, Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary.;Eotvos Lorand Univ, Dept Mat Phys, Pazmany Peter Setany 1-A, H-1117 Budapest, Hungary..
    Li, Wei
    Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden..
    Molnar, David
    Dalarna University, School of Technology and Business Studies, Materials Technology. KTH.
    Kwon, Se Kyun
    Pohang Univ Sci & Technol, Grad Inst Ferrous Technol, Pohang 37673, South Korea..
    Holmstrom, Erik
    Sandvik Coromant R&D, S-12680 Stockholm, Sweden..
    Varga, Bela
    Transylvania Univ Brasov, Fac Mat Sci, Bulevardul Eroilor 29, Brasov 500036, Romania..
    Varga, Lajos Karoly
    Wigner Res Ctr Phys, Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary..
    Vitos, Levente
    Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden.;Wigner Res Ctr Phys, Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary.;Uppsala Univ, Div Mat Theory, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Thermal expansion in FeCrCoNiGa high-entropy alloy from theory and experiment2017In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 110, no 24, article id 241902Article in journal (Refereed)
    Abstract [en]

    First-principle alloy theory and key experimental techniques are applied to determine the thermal expansion of FeCrCoNiGa high-entropy alloy. The magnetic transition, observed at 649 K, is accompanied by a significant increase in the thermal expansion coefficient. The phase stability is analyzed as a function of temperature via the calculated free energies accounting for the structural, magnetic, electronic, vibrational and configurational contributions. The single-and polycrystal elastic modulus for the ferro-and paramagnetic states of the face-centered and body-centered cubic phases are presented. By combining the measured and theoretically predicted temperature-dependent lattice parameters, we reveal the structural and magnetic origin of the observed anomalous thermal expansion behavior. Published by AIP Publishing.

  • 76. Hultquist, G.
    et al.
    Graham, M. J.
    Kodra, O.
    Moisa, S.
    Liu, R.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Smialek, J. L.
    Corrosion of copper in distilled water without O-2 and the detection of produced hydrogen2015In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 95, p. 162-167Article in journal (Refereed)
    Abstract [en]

    This paper reports on hydrogen pressures measured during similar to 19,000 h immersion of copper in oxygen-free liquid distilled water. Copper corrosion products have been examined ex-situ by SEM and characterized by XPS and SIMS. XPS strongly indicates a corrosion product containing both oxygen and hydrogen. SIMS shows that oxygen is mainly present in the outer 0.3 mu m surface region and that hydrogen penetrates to depths well below the corrosion product. Thermal desorption spectroscopy shows that the reaction product formed near room-temperature is less stable than that formed in air at 350 degrees C. 

  • 77. Hultquist, Gunnar
    et al.
    Graham, M. J.
    Kodra, O.
    Moisa, R.
    Liu, R.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Smialek, J. L.
    Corrosion of copper in distilled water without molecular oxygen and the detection of produced hydrogen2013Report (Other academic)
    Abstract [en]

    This paper reports on hydrogen pressures measured during the longterm immersion (~19 000 hours) of copper in oxygen-free distilled water. Hydrogen gas evolution is from copper corrosion and similar pressures (in the mbar range) are measured for copper contained in either a 316 stainless steel or titanium system. Copper corrosion products have been examined ex-situ by SEM and characterized by Xray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). XPS strongly indicates a corrosion product containing both hydroxide and oxide. SIMS shows that oxygen is mainly present in the outer 0.3 um surface region and that hydrogen penetrates to depths in the substrate well below the corrosion product.

  • 78. Hörnström, S. -E
    et al.
    Karlsson, E.
    Losch, A.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Bay, N.
    Forming of high-strength steels using a hot-melt dry lubricant2010In: 17th International Colloquium Tribology 2010 - Solving Friction and Wear Problems, 2010, Vol. 2, p. 958-971Conference paper (Refereed)
    Abstract [en]

    The increasing use of high strength steels in a variety of mechanical engineering applications has illuminated problems associated with galling in sheet metal forming operations. Galling is a tribological phenomenon associated with transfer of material from the steel sheet to the tool surface during forming resulting in seizure of the tool/steel sheet contact and extensive scratching of the steel sheet surface. As a result, a number of concepts have been developed in order to reduce the tendency to galling in metal forming, including the development of new dry lubricants, new forming tool steel grades and improved surface engineering treatments such as the deposition of low friction CVD and PVD coatings. In the present study the performance of a hot-melt dry lubricant in the forming of hot and cold rolled and hot-dip galvanized high strength steel has been evaluated and compared with a conventional rust protection oil using five different tests methods, i.e. a strip reduction test, a bending under tension test, a stretch-forming test, a pin-on disc test and a strip drawing test. In these tests, two different cold work tool steels, a conventional steel grade and a nitrogen alloyed PM steel grade were evaluated. The results show that the different tests used give consistent results and valuable information concerning the galling tendency of the steel sheet, tool steel and lubricant combinations investigated and when combined can be used to rank the galling resistance of lubricants and tool steels. The results clearly show that the dry lubricant provides better lubrication and generates less galling than the rust protection oil. Also, the nitrogen alloyed PM steel grade shows a significantly higher galling resistance as compared with the conventional steel grade and can, in combination with a dry lubricant, preferably be used in sheet metal forming operations to further improve the galling resistance.

  • 79.
    Isgren, Peter
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Dragprovstavens geometripåverkan på mätresultatet2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The thesis is based on a comparative investigation of standard SS 112113 with a geometry described as straight and standard SS-EN 1561:2011 with a geometry described as hourglass shaped. The study will provide deeper understanding of the effect that different tensile test geometries and different test speed has on the tensile strength and the variation. The purpose is to find a suitable geometry and test speed that results in a small dispersion on the measured tensile strength. Another purpose is to perform structural studies to investigate how the microstructure affects the measured result. Seventy tensile tests are included in this study and every bar is casted from the same gray iron melt in identical sand molds. The tensile test bars is lathed according respective standard and tensile tested in a Zwick tensile test machine. A light microscopy, LOM has been used for checking defects in the fracture surface, check the roughness of the surface and for graphite classification. A scanning electron microscope, SEM has been used to check rust on the tensile test piece. Hardness testing by Brinell has been performed since there is a connection between tensile strength and hardness. The tensile strength and the dispersion are lower for SS 112113. The fracture occurs at different positions for standard SS 112113. Different tensile test speed does not result in a significant difference in tensile strength or dispersion. For standard SS-EN 1561:2011 the fracture occurs where the cross-sectional area is minimum. Microstructure with regard to graphite type and graphite length does not explain the difference in tensile strength or deviation.

  • 80.
    Jacobson, S
    et al.
    Uppsala Universitet.
    Beste, U
    Uppsala Universitet.
    Heinrichs, J
    Uppsala Universitet.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Wiklund, U
    Uppsala Universitet.
    On the nature of cemented carbide wear in rock drilling2014In: Hard Rock Tribology Course and Seminar, Tampere, Finland, November 4-5, 2014, 2014Conference paper (Other academic)
  • 81.
    Jacobson, S
    et al.
    Uppsala Universitet.
    Heinrichs, J
    Uppsala Universitet.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    New experimental findings on the role of initial material transfer in determining friction and surface damage,2013In: Proceedings of World Tribology Congress 2013, Torino, Italy, September 8 – 13, 2013, 2013Conference paper (Refereed)
  • 82. Jansson, S.
    et al.
    Brabie, Voicu
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jonsson, P.
    Magnesia-carbon refractory dissolution in Al killed low carbon steel2006In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 33, no 5, p. 389-397Article in journal (Refereed)
    Abstract [en]

    The effects of rotation speed, steel temperature and steel composition on the rate of dissolution of MgO-C refractory into Al deoxidised molten steel were investigated using the rotating cylinder method. Cylinders or rods of MgO-C refractory material were immersed in an Al deoxidised molten steel. Experiments were performed for steel temperatures between 1873 and 1973 K and rotation speeds between 100 and 800 rev min(-1) as well as for different immersion times. For each case, the dissolution rate of MgO-C material was determined from measurement of the decrease in the rod radius. The experimental results showed that the dissolution rate of the MgO-C refractory material increased with an increase in steel temperature and rotation speed. The findings strongly suggest the diffusion of magnesium through the slag layer formed around the refractory rods to be a rate determining step. This thin oxide layer at the steel/refractory interface was found to be owing to reaction between magnesium vapour and CO generated by the reaction between MgO and C in the refractory. Oxide inclusions were also found in the steel melt and they were shown to mainly consist of MgO and Al2O3 or a mixture of the two.

  • 83. Jansson, Sune
    et al.
    Brabie, Voicu
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jonsson, P.
    Corrosion mechanism of commercial doloma refractories in contact with CaO-Al2O3-SiO2-MgO stag2008In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 35, no 2, p. 99-107Article in journal (Refereed)
    Abstract [en]

    The dissolution of three doloma based refractories in liquid CaO-Al2O3-SiO2-MgO slag was studied. Cylindrical refractory specimens of doloma, carbon bonded doloma, and magnesia doloma were rotated in a stationary crucible of molten slag under forced convection conditions. Slag composition, temperature, rod rotation speed and rod immersion time were varied. The refractory dissolution rate was determined from the change in diameter of the cylindrical specimens. The corrosion rate was found to increase with temperature and rod rotation speed and decrease when the slag was nearly saturated with MgO. The findings of the study substantiate the assumption that the diffusion of magnesium oxide through the slag boundary layer controls the corrosion process. The results indicated the overall corrosion process to be the dissolution of refractory material into the slag, followed by slag penetration of the pores and grain boundaries and finally, dispersion of the grains into the slag.

  • 84. Jansson, Sune
    et al.
    Brabie, Voicu
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Josson, Par
    Corrosion mechanism of commercial MgO-C refractories in contact with different gas atmospheres2008In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 48, no 6, p. 760-767Article in journal (Refereed)
    Abstract [en]

    Corrosion of MgO-C refractories in different gas atmospheres consisting of air, Ar, CO or Ar/CO was studied in laboratory experiments. In total, 103 experiments were carried out in the temperature range 1 173 to 1 773 K and for holding times between 2 to 120 min. The reaction rate of the MgO-C material was determined from measurements of the weight loss of the samples. The results showed that the refractory weight loss increased with an increased temperature or an increased holding time. The thermodynamic conditions and the experimental results showed that magnesium gas and carbon monoxide gas should form during ladle refining of steel when the refractory material consists of MgO-C. It was suggested that the reaction rate is directly dependent on the oxygen potential in the ambient atmosphere.

  • 85. Jansson, Sune
    et al.
    Brabie, Voicu
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jönsson, Pär
    Corrosion mechanism and kinetic behaviour of MgO-C refractory material in contact with CaO-Al2O3-SiO2-MgO slag2005In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 34, no 5, p. 283-292Article in journal (Refereed)
    Abstract [en]

    The rate of dissolution of solid MgO-C into liquid CaO-Al2O3-SiO2-MgO slag at different temperatures was studied under conditions of forced convection by rotating cylindrical refractory specimens in a stationary crucible containing molten slag. The corrosion rate was calculated from the change in diameter of the cylindrical refractory specimens. The specimens were rotated for 15-120 min at a speed of 100-400 rpm in the molten slag. The rate of corrosion was found to increase with an increase in temperature and rod rotation speed, and to decrease when the slag was nearly saturated with MgO. The experimental results support the assumption that the diffusion of magnesium oxide through the slag-phase boundary layer controls the corrosion process. The corrosion mechanism seems to be the dissolution of refractory material into the slag followed by penetration of pores and grain boundaries and dispersion of the grains into the slag.

  • 86.
    Johansson, Per
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Mekanisk och tribologisk karakterisering av ferrokrombaserat kompositmaterial för tribologiska användningsområden2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 87.
    Johansson, Robert
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Finite element modeling of straightening of thin-walled seamless tubes of austenitic stainless steel2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    During this thesis work a coupled thermo-mechanical finite element model (FEM) was builtto simulate hot rolling in the blooming mill at Sandvik Materials Technology (SMT) inSandviken. The blooming mill is the first in a long line of processes that continuously or ingotcast ingots are subjected to before becoming finished products.

    The aim of this thesis work was twofold. The first was to create a parameterized finiteelement (FE) model of the blooming mill. The commercial FE software package MSCMarc/Mentat was used to create this model and the programing language Python was used toparameterize it. Second, two different pass schedules (A and B) were studied and comparedusing the model. The two pass series were evaluated with focus on their ability to healcentreline porosity, i.e. to close voids in the centre of the ingot.

    This evaluation was made by studying the hydrostatic stress (σm), the von Mises stress (σeq)and the plastic strain (εp) in the centre of the ingot. From these parameters the stress triaxiality(Tx) and the hydrostatic integration parameter (Gm) were calculated for each pass in bothseries using two different transportation times (30 and 150 s) from the furnace. The relationbetween Gm and an analytical parameter (Δ) was also studied. This parameter is the ratiobetween the mean height of the ingot and the contact length between the rolls and the ingot,which is useful as a rule of thumb to determine the homogeneity or penetration of strain for aspecific pass.

    The pass series designed with fewer passes (B), many with greater reduction, was shown toachieve better void closure theoretically. It was also shown that a temperature gradient, whichis the result of a longer holding time between the furnace and the blooming mill leads toimproved void closure.

  • 88. Karasev, A. V.
    et al.
    Kellner, Hans
    Dalarna University, School of Technology and Business Studies, Materials Technology. KTH.
    Sundqvist, O.
    Memarpour, A.
    Jönsson, P. G.
    Estimation of non-metallic inclusions in industrial Ni based alloys 8252017In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 88, no 4, article id 1600024Article in journal (Refereed)
    Abstract [en]

    It is well known that inclusions affect the properties of the steel and other alloys. The importance of understanding the behavior of the inclusions during production can never be overstated. This study has examined the main types of big size (&gt;10μm) inclusions that exist in Ni-based Alloy at the end of ladle treatment and after casting during industrial production of Ni based Alloys 825. Sources, mechanisms of formation and behavior of different type large size inclusions in Alloy 825 are discussed based on 2 and 3D investigations of inclusion characteristics (such as, morphology, composition, size, and number) and thermodynamic considerations. The large size inclusions found can be divided in spherical (Type I and II) inclusions and in clusters (Type III-V). Type I-A inclusions (Al2O3-CaO-MgO) originate from the slag. Type I-B inclusions and Type II inclusions consist of CaO-Al2O3-MgO and Al2O3-TiO2-CaO, respectively. Both types originate from the FeTi70R alloy. Type III clusters (Al2O3-MgO-CaO) are formed during an Al deoxidation of the Ni-based alloy. Type IV clusters (Al2O3-TiO2-CaO) formed from small inclusions, which are precipitated in local zones which contain high Ti and Al levels. These clusters are transformed to Type III clusters over time in the ladle. Finally, Type V clusters are typical TiN clusters. 

  • 89.
    Karimi Bakhshandi, Reza
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Corrosion Study of yellowmetals in Biodiesel and Test fuel2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Biodiesel is a promising substitute fuel for fossil fuels that derived from renewable resources like vegetable oils and animal fats. Rapeseed methyl ester, RME, is the most common biodiesel used in Scandinavia. Chemically, biodiesel is unstable and degradation of biodiesel results in formation of corrosive degradation products such as short chain fatty acids (SCFA) and water.Degradation of biodiesel is a continuous process which takes place even during corrosion studies in laboratory and results in too aggressive fuel. In order to investigate how increasing acidity of degraded fuel influence corrosion of metals and to avoid too corrosive environment, a stable test fuel simulating degraded biodiesel with certain amount of corrosive degradation products but resistance to additional degradation was needed to be developed.In the first part of this project a stable test fuel has been prepared and doped by adding impurity (methanol) and corrosive degradation products such as SCFA and water to a saturated methyl ester in order to simulate the corrosive environment and avoid excessive aggressiveness during the corrosion testing .Then four batches of test fuel were blended to see how increasing acidity and water content will influence the metallic corrosion.In the second part, samples of copper, brass and aluminium, with focus on copper, were exposed to prepared test fuels and RME in order to investigate corrosion behaviour of the metals and their effect on the test fuels.In order to investigate the stability of test fuel and effect of metals on it, developed test fuels were evaluated regarding to its water content using Karl Fischer volumetric titration, SCFA using extraction ion chromatography, structure using GC-MS and methanol using GC-FID. Targeted acceptance criteria for developed test fuel; such as solubility of degradation products, oxidation stability, toxicity, melting point were fulfilled by test fuel.Corrosion rate of the copper samples was calculated and their surfaces were analysed with SEM-EDS and FTIR. Metal content of fuel samples were analysed after exposure using ICP-OES method.As expected copper accelerated the oxidation of biodiesel effectively and copper ions were released into RME or low acidic test fuel but with increasing the acidity in test fuel copper samples were corroded and the corrosion rate increased. The results showed that the developed test fuel enabled accelerated corrosion testing comparable with aged RME.

  • 90.
    Karlsson, P
    et al.
    Karlstads Universitet.
    Eriksson, Jenny
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Gaard, A
    Karlstads Universitet.
    Krakhmalev, P
    Karlstads Universitet.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Bergstrom, J
    Karlstads Universitet.
    Galling resistance evaluation of tool steels by two different laboratory test methods for sheet metal forming2012In: Lubrication Science, ISSN 0954-0075, E-ISSN 1557-6833, Vol. 24, no 6, p. 263-272Article in journal (Refereed)
    Abstract [en]

    Adhesive accumulation of work material on the tool surface is today a major problem in many sheet metal-forming applications. Different laboratory test methods are used to investigate galling with respect to different tool materials, lubricants and process conditions. In the present study, the galling resistance of a modern nitrogen-alloyed powder metallurgy tool steel and an conventional ingot cast D2 type tool steel was evaluated under lubricated sliding against ferritic stainless steel sheets using a commercial pin-on-disc (POD) and an in-house made slider-on-flat-surface (SOFS) tribotester. The investigated tool steels ranked similarly in terms of galling resistanc in both test methods. However, sliding distances to galling were longer for the SOFS equipment due to continuous sliding on new lubricated sheet surface. Best performance was demonstrated by the powder metallurgy tool steel treated to 65?HRC. Differences in friction behaviour and galling initiation were analysed on the basis of the two different working conditions, i.e. open (SOFS) and closed (POD) tribosystems. Copyright (c) 2012 John Wiley & Sons, Ltd.

  • 91.
    Karlström, Klaudia
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Värmebehandling av kättingstål: Inverkan på slagsegheten och mikrostrukturen2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    One of Ovako:s internal steel grades 9209 is used for chains and thus has high demands on toughness and hardness. After several quality controls has been implemented, among others impact toughness and grain size after martensite hardening, the result of the impact strength was not satisfactory. Several hardening tests in a wide temperature range has been made without satisfactory results. On a few rare occasions, the material had been annealed at 720 °C before hardening. This has resulted in surprisingly high values of impact strength. It’s also been noted that the hardness increases with annealing temperature.

    The main objective of this work is to carry out heat treatments in a temperature range to find the most ideal annealing temperature that maximizes the steel properties and to study the effect of heat treatment on microstructure.

    The result of heat treatment showed that a temperature of 700 °C was the only heat treatment method that resulted in satisfactory impact strength combined with strength requirements.The study of microstructure showed that annealing affects the precipitated particles, which is of probable significance for the ductility and thus improves the impact toughness. Hardness measurements showed that hardness increased with annealing temperature.

  • 92. Kasimagwa, I.
    et al.
    Brabie, Voicu
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jonsson, P. G.
    Slag corrosion of MgO-C refractories during secondary steel refining2014In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 41, no 2, p. 121-131Article in journal (Refereed)
    Abstract [en]

    Studies of the reactions between the MgO-C refractory and a CaO-Al2O3-SiO2-MgO slag system have been carried out through thermodynamic simulations, laboratory experiments and microscopy studies of the microstructure of the refractory samples after the experimental procedures. Corrosion experiments were conducted using the rotating immersion method of the MgO-C refractory rods in a liquid slag: in the temperature range of 1773-1923 K, revolution speed of 200 rev min(-1), with varying slag compositions and times ( 2700-8100 s). Laboratory experiments have shown that the time during which the ladle lining is exposed to a liquid slag with high stirring and slag composition are two important parameters which have large effect on the kinetics of the refractory wear. The rate constants calculated in the present work are in the range of 4 x 10(-7) to 1 x 10(-6) ms(-1). The estimated activation energy from the experimental results is 26 kJ mol(-1)

  • 93.
    Kellner, Hans
    Dalarna University, School of Technology and Business Studies, Materials Technology. KTH, Tillämpad processmetallurgi.
    Study of Non-metallic Inclusion in Alloy 8252017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    It is well known that inclusions affect the properties of steels and alloys. Therefore, it is important to understand what type of inclusions that exist and how they behave and especially with a focus on large size inclusions. Thus, the large size non-metallic inclusions in ferroalloy FeTi70R were investigated in two dimensions (2D) by using scanning electron microscopy (SEM) in combination with an energy dispersive technique (EDS). It was found that the FeTi70R ferroalloy contain complex oxide inclusions consisting mostly of CaO, SiO2 and TiOx. Furthermore, experimental trials were performed to investigate how these inclusions behaved when entering a melt. More specifically, a comparison between pure Fe and an Alloy 825 grade were made. These results determined the parameters effect on the transformation of the inclusions in the melt.

    The large size non-metallic inclusions in Alloy 825 during the ladle treatment were investigated during industrial trials by using both two dimensional (2D) and three dimensional (3D) microscopic investigations. The results showed that inclusions consisted of spherical oxides and clusters made up of oxides and nitrides. Further investigations found that the spherical inclusions were transformed from existing NMI in the FeTi70R ferroalloy and slag particles. As for the clusters, they originate from deoxidation products. Furthermore, small inclusions precipitated in the local zones around the added FeTi70R ferroalloy and titanium nitrides. Investigations also found that only Al2O3-MgO and TiN clusters exist after casting.

    Industrial trials were performed during the last period of the ladle treatment and using a combined electromagnetic (EMS) and gas (GS) stirring. The purpose to investigate the effect of different EMS directions on the agglomeration and on the removal of Al2O3-MgO and TiN clusters. The investigations were then performed in 3D after an electrolytic extraction of the metal samples. The results show that electromagnetic stirring in the upwards direction is best for the agglomeration of the Al2O3-MgO and TiN clusters. However, electromagnetic stirring in the downwards direction is more effective to remove clusters from the melt. This is in agreement with the theoretical predictions based on Stokes’, Brownian and Turbulent collisions. Also, the calculations showed that for Al2O3-MgO clusters with sizes <20 μm the Turbulent collision is the defining factor for agglomeration. However, both Stokes’ and Turbulent collisions are dominant for larger inclusions. For the TiN clusters, turbulent collisions is the dominant factor.

    Further investigations with more heats and stirring modes were done by using 2D microscopic investigations. More specifically, the number, size, composition and morphology of different inclusions were determined by using SEM in combination with EDS and Inca Feature analyses. The results show that the EMS in downwards direction with a 0.04 m3 min-1 gas flow rate promotes a general removal of Al2O3-MgO and TiN inclusions. Furthermore, that the upwards EMS direction promotes a drastically increase of inclusions having an equivalent size smaller than 11.2 μm. Moreover, the stirring with a 0.02 m3 min-1 gas flow rate has a better removal rate for both downwards and upwards stirring directions compared to the stirring with a 0.04 m3 min-1 gas flow rate. However, no influence on the inclusion composition and morphology could be seen from the different stirring modes.

  • 94.
    Kellner, Hans
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Karasev, A. V.
    Memarpour, A.
    Jönsson, P. G.
    Evolution of non-metallic inclusions from FeTi70R alloys during alloying of Fe-40Ni-20Cr steels2016In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 87, no 11, p. 1461-1468Article in journal (Refereed)
    Abstract [en]

    In this study, the composition, size, and number of large non-metallic inclusions (&gt;20μm) are investigated in a commercial refined FeTi70R alloy, which is used for deoxidation and alloying of different industrial high-quality steels. It is found that this ferroalloy contains different complex oxide inclusions, which sizes vary from 20 to 260μm. These different complex inclusions contain mostly CaO, SiO2, and TiOx. When adding FeTi70R alloy in the steel during the final stage of ladle treatment, these large size inclusions can significantly decrease the cleanliness and mechanical properties of steel. Therefore, the evolution and behavior of these inclusions after addition of this ferroalloy into the liquid iron or Fe-40Ni-20Cr steel are investigated in laboratory experiments. In addition, the results from the laboratory scale experiments are compared to results obtained from industrial heats using Alloy 825. A consideration of the evolution mechanism of large inclusions after an addition of a FeTi70R alloy helps to understand their behavior in the melt. It also helps to estimate their possible harmful effects on the quality of this steel grade during commercial production. 

  • 95.
    Kellner, Hans
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology. KTH.
    Karasev, A. V.
    Sundqvist, O.
    Jönsson, P. G.
    Effect of the Stirring Mode on the Behavior of Al2O3–MgO Particles and Clusters during Ladle Treatment of Ni-based Alloy 8252017In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 88, no 12, article id 1700165Article in journal (Refereed)
  • 96.
    Kellner, Hans
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology. KTH.
    Karasev, Andrey Vladimirovich
    KTH Royal Inst Technol, S-10044 Stockholm, Sweden..
    Sundqvist, Olle
    Sandvik Mat Technol AB, S-81181 Sandviken, Sweden..
    Jönsson, Pär Göran
    KTH Royal Inst Technol, S-10044 Stockholm, Sweden..
    TiN Particles and Clusters during Ladle Treatments of Ni-based Alloy 825 using Different Stirring Modes2018In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 58, no 2, p. 292-298Article in journal (Refereed)
    Abstract [en]

    Today, titanium is often used in steelmaking not only for deoxidation but also for micro-alloying and alloying for a wide range of steel grades. Therefore, many studies are focused on investigations on the formation and behavior of Ti-containing non-metallic inclusions (such as oxides, nitrides and carbides) during production of different Ti-containing steels and their effect on final steel properties. This study has examined the behavior of TiN clusters and particles in the melt during the ladle treatment of Alloy 825 containing up to 1.2 wt% of Ti. The industrial trials were performed at the end of the ladle treatment by using argon gas in combination with electromagnetic stirring using an upwards or a downwards stirring direction. Metal samples were taken before and after ladle treatment to enable three-dimensional investigations of non-metallic inclusions and clusters. The composition, size and number of particles and clusters were determined after electrolytic extraction of the metal samples by using SEM in combination with EDS. It was found that agglomerations of TiN clusters and particles in the melt are faster during an upwards stirring in comparison to a downwards stirring. However, the removal of clusters from the melt is more effective when using a downwards stirring direction compared to when using an upwards stirring in combination with gas stirring. It was also found that the Turbulent collision is the dominant factor for the agglomeration of TiN particles in the melt.

  • 97.
    Khraisat, Walid
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Graphite pore filling and surface blistering of sintered Fe-C-Si2012In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 55, no 3, p. 242-247Article in journal (Refereed)
    Abstract [en]

    Different alloys of the system Fe-C-Si were sintered to obtain a grey iron microstructure and then hardened by post-sintering heat treatment to obtain a martensitic structure. The main problem in the development of this approach is related to the occurrence of surface blistering in the as sintered material when sintering in N2 atmosphere. Surface blistering is explained by the increase in entrapped gas pressure in pores caused by graphite pore filling. A mechanism has been proposed to explain graphite pore filling. According to this mechanism, graphite pore filling is caused by the C activity difference between the gas entrapped in pores and the matrix, which is a consequence of Boudouard’s reaction. This difference in C activity causes C to diffuse from the matrix to the pores, thus filling pores with graphite. © 2012 Institute of Materials, Minerals and Mining.

  • 98.
    Kolvereid, Anneli
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Framtagande av fördelningsfaktorer för säkrare beräkning vid skrotlastning2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This work is performed at the company Ovako Sweden AB in Hofors as a degree project for the engineering education in materials technology.  In steel industry, the cost of raw materials such as scrap and alloys is the by far largest, and requires resources for the best utilization. By using a program to optimize the loading of scrap, large savings can be made. The thesis presents the compiling of distribution factors for more secure calculations for the scrap loading. These factors are used in the optimization program RAWMATMIX as large savings can be made since this program chooses the most economically advantageous raw material. The results show that the distribution factors differ between different scrap classes, which require a new model for the distribution factors for each class. Furthermore, the optimization program must be adapted to calculate with a certain amount of steel left in the electric arc furnace. 

  • 99. Larsson, C.
    et al.
    Holden, T. M.
    Bourke, M. A. M.
    Stout, M.
    Teague, J.
    Lindgren, Lars-Erik
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Measurement andniodeling of residual stress in a welded Haynes (R) 25 cylinder2005In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 399, no 1-2, p. 49-57Article in journal (Refereed)
    Abstract [en]

    An experimental and simulation study of residual stresses was made in the vicinity of a gas tungsten arc weld, used to join a hemispherical end cap to a cylinder. The capped cylinder is used in a satellite application and was fabricated from a Co-based Haynese (R) 25 alloy. The cylinder was 34.7 mm in outer diameter and 3.3 mm in thickness. The experimental measurements were made by neutron diffraction and the simulation used the implicit Marc finite element code. The experimental resolution was limited to approximately 3 rum parallel to the axis of the cylinder (the weld was 6 mm in the same direction) and comparison over the same volume of the finite element prediction showed general agreement. Subject to the limited spatial resolution, the largest experimentally measured tensile residual stress was 180 MPa, located at the middle of the weld. However, the predictions suggest that there are regions in the weld where average tensile residual stresses as much as 400 MPa exist. One qualitative disparity between the model and the experiments was that the measurement included a larger degree of asymmetry on either side of the weld than predicted by the model. 

  • 100. Lindgren, L. -E
    et al.
    Gyhlesten Back, Jessica
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Elastic properties of ferrite and austenite in low alloy steels versus temperature and alloying2019In: Materialia, ISSN 2589-1529, Vol. 5, article id 100193Article in journal (Refereed)
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