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  • 201.
    Memarpour, Arashk
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Brabie, Voicu
    Jönsson, Pär G.
    Decarburization and clogging behaviour of yttria stabilized zirconia coatings applied to SEN´s Al2O3-C refractories by plasma PVD2012In: Steel Grips - Journal of Steel and Related Materials, ISSN 1611-4442, E-ISSN 1866-8453, Vol. 10, p. 353-363Article in journal (Refereed)
    Abstract [en]

    Carbon oxidation is a main industrial problem for alumina-graphite refractory base materials used in commercial Submerged Entry Nozzles (SEN) during preheating. Thus, the effects of the plasma spray-PVD coating of the Yttria Stabilized Zirconia (YSZ) powder on the carbon oxidation were investigated. Laboratory preheating trials were performed at non-isothermal heating conditions in a controlled atmosphere. Also, the applied temperature profile for the laboratory trials were defined based on industrial preheating trials. The controlled atmospheres consisted of CO2, O2 and Ar. The (CO2/O2) ratios were kept the same as for a propane combustion flue gas at an Air-Fuel-Ratio (AFR) value equal to 1.5 for heating in an air-fuel mixture and in air. The thicknesses of the decarburized layers were measured and examined using light optic microscopy, FEG-SEM and EDS. The YSZ plasma-PVD coated alumina-graphite refractory base materials, presented the effective resistance to carbon oxidation at different coating thicknesses from 160-480 µm in both combustion flue gas and air atmospheres. For the YSZ plasma coating that contained a thinner coating layer such as 160 µm, the uneven surface of the substrate may be reflected more than it could be reflected for a thicker coating. However, for the YSZ plasma coating with a coating thickness of 290 µm, the uneven surface of the substrate may be reflected much less than it could be reflected for thinner coatings. A 250µm and a 290µm YSZ coating may prevent the decarburization of an alumina-graphite refractory base materials during preheating in air at a maximum heating temperature of 1020°C. Moreover, in an oxidizing atmosphere with an AFR value equal to 1.5 at a maximum temperature of 1020°C and a holding time of 7200 seconds. A 250-290 µm YSZ coating is suggested to be an appropriate coating, as it provides both an even surface and prevention of the decarburization even during heating in air. In addition, the interactions between the YSZ coated alumina-graphite refractory base materials in contact with a cerium alloyed molten stainless steel were surveyed. The YSZ coating provided a total prevention of the alumina reduction by cerium. Therefore, the prevention of the first clogging product formed on the surface of the SEN refractory base materials. Therefore, the YSZ plasma-PVD coating can be recommended for coating of the hot surface of the commercial SENs.

  • 202.
    Memarpour, Arashk
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Brabie, Voicu
    Dalarna University, School of Technology and Business Studies, Material Science.
    Jönsson, Pär G.
    Post-mortem study of the internal coated SENs (Submerged Entry Nozzle) respecting clogging phenomena2011Conference paper (Refereed)
    Abstract [en]

    A large number of accretion samples formed inside alumina/graphite clogged Submerged Entry Nozzles (SEN) were examined using FEG-SEM-EDS and Feature analysis. The SENs were used for continuous casting of stainless steel grades alloyed by Rare Earth Metals (REM). The internal surfaces of the SENs were coated by a glass/silicon powder layer to prevent the SEN decarburization during the preheating process. The results indicated a harmful effect of the SENs decarburization on the accretion thickness. In addition, the post-mortem results clearly revealed the formation of a multi-layer accretion. Also, the study indicated the penetration of the protecting glaze into the Alumina/graphite refractory materials. The interaction of the penetrated glaze with alumina in the SEN refractory materials leads to formation of high viscous alumina-rich glaze during the SEN preheating process. This interaction may lead to formation of an uneven surface inside the SEN. These areas consist of alumina particles, silica particles and the penetrated glaze in between. The results showed that these areas react with dissolved REM in molten steel to form REM aluminates, REM silicates and REM alumina-silicates. Furthermore, the penetration of the glaze may lead to reactions between alkalines in the glaze and the graphite. This leads to a supply of oxygen at the interface between the SEN and the molten steel. This, in turn, may lead to reoxidation of the REM alloying elements in molten steel under the formation of “in situ” REM oxides. The formation of the large “in-situ” REM oxides and the reaction of the REM alloying elements with the SEN´s uneven inside surface, may create a large REM-rich surface in contact with the primary inclusions in molten steel. This may facilitate the attraction and agglomeration of the primary REM oxides inclusions on the SEN internal surface and thereafter the clogging.

  • 203.
    Memarpour, Arashk
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Brabie, Voicu
    Dalarna University, School of Technology and Business Studies, Material Science.
    Jönsson, Pär G.
    The effect of zirconium disilicide (ZrSi2) additions on the carbon oxidation behavior of alumina/graphite refractory materials2010In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, no 11, p. 1612-1621Article in journal (Refereed)
    Abstract [en]

    Carbon oxidation is a main industrial problem for Alumina/Graphite Submerged Entry Nozzles (SEN) during pre-heating. Thus, the effect of ZrSi2 antioxidants and the coexistence of antioxidant additive and (4B2O3 •BaO) glass powder on carbon oxidation were investigated at simulated non-isothermal heating conditions in a controlled atmosphere. Also, the effect of ZrSi2 antioxidants on carbon oxidation was investigated at isothermal temperatures at 1473 K and 1773 K. The specimens’ weight loss and temperature were plotted versus time and compared to each others. The thickness of the oxide areas were measured and examined using XRD, FEG-SEM and EDS. The coexistence of 8 wt% ZrSi2 and 15 wt% (4B2O3 •BaO) glass powder of the total alumina/Graphite base refractory materials, presented the most effective resistance to carbon oxidation. The 121% volume expansion due to the Zircon formation during heating and filling up the open pores by (4B2O3 •BaO) glaze during green body sintering led to an excellent carbon oxidation resistance.

  • 204.
    Michael, Lindgren
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Experimental investigations of the roll load and roll torque when high strength steel is roll formed2007In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 191, no 1-3, p. 44-47Article in journal (Refereed)
    Abstract [en]

    The cold roll forming process is a highly efficient process used to produce profiles for many applications, for example vehicles, buildings, domestic machines, etc. Therefore, its market share is increasing every year. Many of the above products are already today made of high strength steel and the usage of these materials will likely continue to increase. The objectives of this project are to find howthe roll load and roll torque are influenced by the yield strength of the material. Full-scale experiments have been performed. U-channels made of different materials from mild to ultra high strength steels have been formed. The roll torque is measured during the process using a torque sensor mounted between the tool and the power transmission. Used power is also calculated with help of the motor current. The roll load is measured with load cells mounted on both side of the roll forming tool. The experimental result will increase the understanding of the specific conditions for roll forming steels with increasing yield strength. The result can be used to support the roll machine designer to choose machine elements and power unit for these applications. Furthermore, the result can also be compared with finite element simulations in order to improve and validate simulation models.

  • 205.
    Molnar, David
    Dalarna University, School of Technology and Business Studies, Materials Technology. KTH, Tillämpad materialfysik.
    Generalised stacking fault energy and plastic deformation of austenitic stainless steels2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Austenitic stainless steels are primarily known for their exceptional corrosion resistance. They have the face centred cubic (FCC) structure which is stabilised by adding nickel to the Fe-Cr alloy. The Fe-Cr-Ni system can be further extended by adding other elements such as Mn, Mo, N, C, etc. in order to improve the properties. Since austenitic stainless steels are often used as structural materials, it is important to be able to predict their mechanical behaviour based on their composition, microstructure, magnetic state, etc.

    In this work, we investigate the plastic deformation behaviour of austenitic stainless steels by theoretical and experimental approaches. In FCC materials the stacking fault energy (SFE) plays an important role in the prediction of the deformation modes. Based on the magnitude of the SFE different deformation modes can be observed such as martensite formation, deformation twinning, dissociated or undissociated dislocation glide. All these features influence the behaviour differently, therefore it is desired to be able to predict their occurrence. Alloying and temperature have strong effect on the SFE and thus on the mechanical properties of the alloys. Several models based on the SFE and more recently on the so called generalised stacking fault energy (GSFE or γ-surface) are available to predict the alloy's affinity to twinning and the critical twinning stress representing the minimum resolved shear stress required to initiate the twinning deformation mechanism. One can employ well established experimental techniques to measure the SFE. On the other hand, one needs to resort to ab initio calculations based on density functional theory (DFT) to compute the GSFE of austenitic steels and derive parameters like the twinnability and the critical twinning stress. 

    We discuss the effect of the stacking fault energy on the deformation behaviour for two different austenitic stainless steels. We calculate the GSFE of the selected alloys and based on different models, we predict their tendency for twinning and the critical twinning stress. The theoretical predictions are contrasted with tensile tests and electron backscatter diffraction (EBSD) measurements. Several conventional and in situ tensile test are performed to verify the theoretical results. We carry out EBSD measurements on interrupted and fractured specimens and during tensile tests to closely follow the development of the microstructure. We take into account the role of the intrinsic energy barriers in our predictions and introduce a new and so far unique way to experimentally obtain the GSFE of austenitic stainless steels. Previously, only the SFE could be measured precisely by well-designed experiments. In the present thesis we go further and propose a technique that can provide accurate unstable stacking fault energy values for any austenitic alloy exhibiting twinning. 

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    FULLTEXT01
  • 206.
    Molnar, David
    Dalarna University, School of Technology and Business Studies, Materials Technology. KTH, Tillämpad materialfysik.
    Stacking fault energy and deformation behaviour of austenitic stainless steels: a joint theoretical-experimental study2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Austenitic stainless steels are primarily known for their exceptional corrosion resistance. They have the face centred cubic (FCC) structure which is stabilised by adding nickel, manganese or nitrogen to the Fe-Cr alloy. The Fe-Cr-Ni system can be further extended by adding other elements such as Mo, Cu, Ti, C, etc. to improve the properties. Since austenitic stainless steels are often used as structural materials, it is important to be able to predict their mechanical behaviour based on their composition, microstructure, magnetic state, etc.

    In this work, the plastic deformation behaviour of austenitic stainless steels is investigated by theoretical and experimental approaches. In FCC materials the stacking fault energy (SFE) plays an important role in the description and prediction of the deformation modes. Based on the magnitude of the SFE different deformation modes can be observed such as martensite formation, deformation twinning, or dislocation glide. All these deformation modes influence the material behaviour, therefore it is desired to predict and control their occurrence. Alloying elements and temperature have a strong effect on the SFE and thus on the mechanical properties of the alloys. Several models based on the SFE and more recently on the so-called generalised stacking fault energy (GSFE or γ-surface) are available to describe the alloy's affinity to twinning and the critical twinning stress representing the minimum resolved shear stress required to initiate the deformation twinning mechanism. One can employ well established experimental techniques to measure the SFE. On the other hand, one needs to resort to ab initio calculations based on density functional theory (DFT) to compute the GSFE of austenitic steels and derive parameters like the twinnability and the critical twinning stress.

    The correlation between the stacking fault energy and the deformation behaviour for four different austenitic stainless steels is discussed in this work. The SFE of the selected alloys is obtained by ab initio calculations and based on different models, their tendency for twinning and their critical twinning stress is predicted. The mechanical behaviour and the affinity for twinning and martensitic transformation is mapped across a broad range of temperature (-70°C to +500°C) for the four alloys. The theoretical predictions are contrasted with tensile tests and electron backscatter diffraction (EBSD) measurements. Several conventional and in situ tensile test are performed to verify the theoretical results. EBSD measurements on interrupted and fractured specimens, and during in situ tensile tests were carried out to closely follow the development of the microstructure. In the present thesis, a technique is proposed that can provide accurate unstable stacking fault energy values for any austenitic alloy exhibiting twinning at low stress values. The importance of temperature and interstitial alloying on mechanical behaviour is also investigated.

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    FULLTEXT01
  • 207.
    Molnar, David
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology. KTH.
    Engberg, Göran
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Li, Wei
    Lu, Song
    Hedström, Peter
    Kwon, Se Kyun
    Vitos, Levente
    Experimental study of the gamma-surface of austenitic stainless steels2019In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 173, p. 34-43Article in journal (Refereed)
    Abstract [en]

    We introduce a theory-guided experimental approach to study the γ-surface of austenitic stainless steels. The γ-surface includes a series of intrinsic energy barriers (IEBs), which are connected to the unstable stacking fault (USF), the intrinsic stacking fault (ISF), the unstable twinning fault (UTF) and the extrinsic stacking fault (ESF) energies. The approach uses the relationship between the Schmid factors and the effective energy barriers for twinning and slip. The deformation modes are identified as a function of grain orientation using in situ electron backscatter diffraction measurements. The observed critical grain orientation separating the twinning and slip regimes yields the USF energy, which combined with the universal scaling law provides access to all IEBs. The measured IEBs and the critical twinning stress are verified by direct first-principles calculations. The present advance opens new opportunities for modelling the plastic deformation mechanisms in multi-component alloys.

  • 208.
    Molnar, David
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology. KTH.
    Engberg, Göran
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Li, Wei
    Vitos, Levente
    Deformation properties of austenitic stainless steels with different stacking fault energies2018In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 941, p. 190-197Article in journal (Refereed)
    Abstract [en]

    In FCC metals a single parameter – stacking fault energy (SFE) – can help to predict the expectable way of deformation such as martensitic deformation, deformation twinning or pure dislocation glide. At low SFE one can expect the perfect dislocations to dissociate into partial dislocations, but at high SFE this separation is more restricted. The role of the magnitude of the stacking fault energy on the deformation microstructures and tensile behaviour of different austenitic steels have been investigated using uniaxial tensile testing and electron backscatter diffraction (EBSD). The SFE was determined by using quantum mechanical first-principles approach. By using plasticity models we make an attempt to explain and interpret the different strain hardening behaviour of stainless steels with different stacking fault energies.

  • 209.
    Molnar, David
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology. KTH.
    Lu, Song
    Hertzman, Staffan
    Engberg, Göran
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Vitos, Levente
    Study of the alternative mechanism behind the constant strain hardening rate in high‑nitrogen steels2020In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 170, article id 110726Article in journal (Refereed)
    Abstract [en]

    In this study, three austenitic stainless steels with different compositions are compared in terms of their deformation behaviour. Two of the investigated steels have considerable high nitrogen content which affects their deformation behaviour. The deformation properties and microstructure of the materials were studied by tensile testing and electron backscatter diffraction. We observe that the strain hardening rate curve of the alloy with low nitrogen content shows a continuously decreasing slope, whereas those of the high‑nitrogen steels exhibit a clear plateau. Since no twinning or ε-phase formation is observed at the corresponding strain levels, we suggest that the addition of a large amount of nitrogen suppresses cross-slip and promotes dislocation planarisation. The microstructural evolution of the materials during deformation supports the above scenario. Based on the results of the ab initio calculations, the deformation behaviour of high‑nitrogen alloys cannot be explained in terms of the stacking fault energy.

  • 210.
    Molnar, David
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology. KTH.
    Sun, Xun
    Lu, Song
    Li, Wei
    Engberg, Göran
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Vitos, Levente
    Effect of temperature on the stacking fault energy and deformation behaviour in 316L austenitic stainless steel2019In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 759, p. 490-497Article in journal (Refereed)
    Abstract [en]

    The stacking fault energy (SFE) is often used as a key parameter to predict and describe the mechanical behaviour of face centered cubic material. The SFE determines the width of the partial dislocation ribbon, and shows strong correlation with the leading plastic deformation modes. Based on the SFE, one can estimate the critical twinning stress of the system as well. The SFE mainly depends on the composition of the system, but temperature can also play an important role. In this work, using first principles calculations, electron backscatter diffraction and tensile tests, we show a correlation between the temperature dependent critical twinning stress and the developing microstructure in a typical austenitic stainless steel (316L) during plastic deformation. We also show that the deformation twins contribute to the strain hardening rate and gradually disappear with increasing temperature. We conclude that, for a given grain size there is a critical temperature above which the critical twinning stress cannot be reached by normal tensile deformation, and the disappearance of the deformation twinning leads to lower strain hardening rate and decreased ductility.

  • 211.
    Molnar, David
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology. KTH.
    Vida, Ádám
    Huang, Shuo
    Chinh, Nguyen Q
    The effect of cooling rate on the microstructure and mechanical properties of NiCoFeCrGa high-entropy alloy2019In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 54, no 6, p. 5074-5082Article in journal (Refereed)
    Abstract [en]

    The effect of cooling rate on the microstructure and mechanical properties of equimolar NiCoFeCrGa high-entropy alloy (HEA) was studied by scanning electron microscopy, energy-dispersive X-ray spectroscopy and electron backscatter diffraction (EBSD), as well as by microhardness tests. Experimental results show that the cooling rate has a crucial impact on the developing microstructure which has a mixture of two—FCC and BCC—phases, leading to a self-similarity of the solidified structure formed in the sample. Furthermore, the cooling rate influences both the composition of the two phase-components and the ratio of their volume fractions, determining the mechanical properties of the sample. The present results confirm the grouping of Co, Fe and Cr in the FCC phase and that of Ni and Ga in BCC phase in the NiCoFeCrGa high-entropy alloy system. An empirical rule is suggested to predict how the phase-components can be expected in this complex high-entropy alloy.

  • 212.
    Mukhopadhyay, N K
    et al.
    a Centre of Advanced Study, Department of Metallurgical Engineering, Institute of Technology, Banaras Hindu University, Varanasi 221 005, India.
    Ali, Fahad
    IFW Dresden, Institut für Komplexe Materialien, Postfach 27 01 16, D-01171 Dresden, Germany.
    Srivastava, Vikas C
    National Metallurgical Laboratory, Jamshedpur-831 007, India.
    Yadav, T P
    Department of Physics, Banaras Hindu University, Varanasi 221 005, India.
    Sakaliyska, Miroslava
    IFW Dresden, Institut für Komplexe Materialien, Postfach 27 01 16, D-01171 Dresden, Germany.
    Surreddi, Kumar Babu
    IFW Dresden, Institut für Komplexe Materialien.
    Scudino, Sergio
    IFW Dresden, Institut für Komplexe Materialien, Postfach 27 01 16, D-01171 Dresden, Germany.
    Uhlenwinkel, Volker
    Institut für Werkstofftechnik, Universität Bremen, Badgasteiner Str. 3, D-28359 Bremen, Germany.
    Eckert, Jürgen
    IFW Dresden, Institut für Komplexe Materialien, Postfach 27 01 16, D-01171 Dresden, Germany.
    Strain-induced structural transformation of single-phase Al–Cu–Fe icosahedral quasicrystal during mechanical milling2011In: Philosophical Magazine, ISSN 1478-6435, Vol. 91, no 19-21, p. 2482-2490Article in journal (Refereed)
  • 213. Nath, Deo
    et al.
    Tiwari, S. N.
    Surreddi, Kumar Babu
    Banaras Hindu University, India.
    Structure and properties of Al–Ni PM composites2004In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 47, no 3, p. 247-252Article in journal (Refereed)
    Abstract [en]

    Al–Ni powder mixtures containing 2, 4, 6 and 8 wt-% nickel were compacted at 125, 250, 375 and 500 MPa and sintered at 620, 630 and 640°C in a nitrogen atmosphere. The sintered density, sintered hardness and strength of composites thus produced were determined as a function of compaction pressure and sintering temperature. Wear rates of the composites were evaluated as a function of applied load and sliding velocity. Optical and scanning electron microscopy were used to reveal the morphology of powder and microstructures of green and sintered compacts. X-ray diffraction studies of the sintered compacts were made to confirm the phases formed on sintering. Sintered density, sintered hardness and strength increased with an increase in compaction pressure and nickel content. X-ray diffraction indicated the presence of Al3Ni phase in the sintered alloy. The wear rate of the sintered Al–Ni PM composite was found to increase with increasing load and decrease with increasing nickel content.

  • 214.
    Nikolowski, K
    et al.
    IFW Dresden, Institut für Komplexe Materialien, Postfach 27 01 16, D-01171 Dresden, Germany.
    Scudino, Sergio
    IFW Dresden, Institut für Komplexe Materialien, Postfach 27 01 16, D-01171 Dresden, Germany.
    Stoica, Mihai
    IFW Dresden, Institut für Komplexe Materialien, Postfach 27 01 16, D-01171 Dresden, Germany.
    Surreddi, Kumar Babu
    IFW Dresden, Institut für Komplexe Materialien.
    Das, Jayanta
    IFW Dresden, Institut für Komplexe Materialien, Postfach 27 01 16, D-01171 Dresden, Germany.
    Eckert, Jürgen
    IFW Dresden, Institut für Komplexe Materialien, Postfach 27 01 16, D-01171 Dresden, Germany.
    Stress-induced martensitic transformation in a Ti45Zr38Al17 cast rod2009In: Journal of Physics: Conference Series, ISSN 1742-6588, Vol. 144, no 1, p. 1-4Article in journal (Refereed)
  • 215.
    Nilsson, Maria
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Tribology in Metal Working2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis focuses on the tribological performance of tool surfaces in two steel working operations, namely wire drawing and hot rolling. In all forming operations dimensions and surface finish of the products are of utmost importance. Forming basically includes three parts – forming conditions excluded – that may be changed; work material, tool and (possibly) lubricant. In the interface between work material and tool, the conditions are very aggressive with – generally or locally – high temperatures and pressures. The surfaces will be worn in various ways and this will change the conditions in the process. Consequently, the surface finish as well as the dimensions of the formed product may change and in the end, the product will not fulfil the requirements of the customer. Therefore, research and development in regard to wear, and consequently tribology, of the forming tools is of great interest.

    The investigations of wire drawing dies focus on coating adhesion/cohesion, surface characteristics and material transfer onto the coated steel both in laboratory scale as well as in the wire drawing process. Results show that it in wire drawing is possible to enhance the tribological performance of drawing dies by using a lubricant together with a steel substrate coated by a polished, dual-layer coating containing both hard and friction-lowering layers.

    The investigations of hot rolling work rolls focus on microstructure and hardness as well as cracking- and surface characteristics in both laboratory scale and in the hot strip mill. Results show that an ideal hot work roll material should be made up of a matrix with high hardness and a large amount of complex, hard carbides evenly distributed in the microstructure. The surface failure mechanisms of work rolls are very complex involving plastic deformation, abrasive wear, adhesive wear, mechanical and thermal induced cracking, material transfer and oxidation.

    This knowledge may be used to develop new tools with higher wear resistance giving better performance, lower costs and lower environmental impact.

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  • 216.
    Nilsson, Maria
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    An investigation of worn work roll materials used in the finishing stands of the hot strip mill for steel rolling2012Conference paper (Refereed)
    Abstract [en]

    The surface failure characteristics of different work roll materials, i.e. High Speed Steel, High Chromium Iron and Indefinite Chill Iron, used in the finishing stands of a hot strip mill have been investigated using stereo microscopy, 3D optical profilometry, scanning electron microscopy and energy dispersive X-ray spectroscopy. The results show that the surface failure mechanisms of work rolls for hot rolling are very complex, involving plastic deformation, abrasive wear, adhesive wear, mechanical and thermal induced cracking, material transfer and oxidation. Despite the differences in chemical composition and microstructure, the tribological response of the different work roll materials was found to be strongly dependent on the material microstructure and especially the presence and distribution of microstructural constituents, such as the different carbide phases and graphite (in the case of Indefinite Chill Iron). Cracking and chipping of the work roll surfaces, both having a negative impact on work roll wear, are strongly influenced by the presence of carbides, carbide networks and graphite in the work roll surface. Consequently, the amount of carbide forming elements as well as the manufacturing process must be controlled in order to obtain an optimised microstructure and a predictable wear rate.

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    An investigation of worn work roll materials used in the finishing stands of the hot strip mill for steel rolling
  • 217.
    Nilsson, Maria
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    An investigation of worn work roll materials used in the finishing stands of the hot strip mill for steel rolling2013In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 227, no 8, p. 837-844Article in journal (Refereed)
    Abstract [en]

    The surface failure characteristics of different work roll materials, i.e. High Speed Steel, High Chromium Iron and Indefinite Chill Iron, used in the finishing stands of a hot strip mill have been investigated using stereo microscopy, 3D optical profilometry, scanning electron microscopy and energy dispersive X-ray spectroscopy. The results show that the surface failure mechanisms of work rolls for hot rolling are very complex, involving plastic deformation, abrasive wear, adhesive wear, mechanical and thermal induced cracking, material transfer and oxidation. Despite the differences in chemical composition and microstructure, the tribological response of the different work roll materials was found to be strongly dependent on second phase constituents such as the size, morphology and distribution of different carbide phases and graphite (in the case of Indefinite Chill Iron) which was found to promote cracking. Cracking and chipping of the work roll surfaces, both having a negative impact on work roll wear, are strongly influenced by the presence of carbides, carbide networks and graphite in the work roll surface. Consequently, the amount of carbide forming elements as well as the manufacturing process must be controlled in order to obtain an optimised microstructure and a predictable wear rate.

  • 218.
    Nilsson, Maria
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology. Tribomaterials group, The Ångström Laboratory, Uppsala University, Sweden.
    Microstructural, mechanical and tribological characterisation of roll materials for the finishing stands of the hot strip mill for steel rolling2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 307, no 1-2, p. 209-217Article in journal (Refereed)
    Abstract [en]

    The microstructure, mechanical and tribologicalproperties for three different materials, High Speed Steel, High Chromium ironand Indefinite Chill iron, used for hot strip mill work rolls have beenevaluated. Microstructural characterisation was performed using light opticalmicroscopy, scanning electron microscopy and energy dispersive X-rayspectroscopy. The mechanical and tribological properties were evaluated usingmicro Vickers indentation and scratch testing in combination with post-testmicroscopy. The microstructures of the investigated materials were found to berather complex with a number of secondary phases andalso materials with similar nominal composition display significant differenceswith respect to distribution, size and morphology of carbides. Scratch testing,including detection of friction coefficient, acoustic emission and penetrationdepth, gives valuable information concerning the mechanical and tribologicalresponse on a microscopic level of the investigated materials. Type,amount, distribution, size and morphology of the secondary phases in thematerials have a strong impact on the surface deformation and wear mechanismsduring scratching. Cracking and chipping are frequently observed in connectionto the ridges surrounding the scratches. However, cross-sectional analyses ofthe scratched microstructures reveal that cracking of the brittle carbidephases may extend to significant depths, >100 µm, reducing the mechanicalstrength of the material. Based on the results, it is believed that a moreisotropic microstructure, e.g. obtained via a powder metallurgy process, withfiner carbides would result in improved properties and performance in a hotrolling application.

  • 219.
    Nilsson, Maria
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Tribological Testing of Some Potential PVD and CVD Coatings for Steel Wire Drawing Dies2010In: Nordtrib 2010, Storforsen, 2010Conference paper (Refereed)
    Abstract [en]

    Cemented carbide is today the most frequently used drawing die material in steel wire drawing applications. This is mainly due to the possibility to obtain a broad combination of hardness and toughness thus meeting the requirements concerning strength, crack resistance and wear resistance set by the wire drawing process. However, the increasing cost of cemented carbide in combination with the possibility to increase the wear resistance of steel through the deposition of wear resistant CVD and PVD coatings have enhanced the interest to replace cemented carbide drawing dies with CVD and PVD coated steel wire drawing dies. In the present study, the possibility to replace cemented carbide wire drawing dies with CVD and PVD coated steel drawing dies have been investigated by tribological characterisation, i.e. pin-on-disc and scratch testing, in combination with post-test observations of the tribo surfaces using scanning electron microscopy, energy dispersive X-ray spectroscopy and 3D surface profilometry. Based on the results obtained, CVD and PVD coatings aimed to provide improved tribological performance of steel wire drawing dies should display a smooth surface topography, a high wear resistance, a high fracture toughness (i.e. a high cracking and chipping resistance) and intrinsic low friction properties in contact with the wire material. Also, the steel substrate used must display a sufficient load carrying capacity and resistance to thermal softening. Of the CVD and PVD coatings evaluated in the tribological tests, a CVD TiC and a PVD CrC/C coating displayed the most promising results.

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  • 220. 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.

  • 221.
    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)
  • 222.
    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.

  • 223.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    A new test method for measuring the galling resistance between metal powders and die tool materials in powder compaction2011In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 273, no 1, p. 49-54Article in journal (Refereed)
    Abstract [en]

    The friction characteristics and galling resistance between metal powder and die tool material in metal powder compaction is of outmost importance since they will influence the porosity and surface quality of the green body and consequently the porosity, tolerances and surface quality of the final sintered product. In the present study, a new test method for evaluating the tribological performance of die tool materials aimed for powder compaction is presented. The test method is based on controlled scratch testing using a commercial scratch tester but instead of the commonly used Rockwell C diamond stylus a sample holder with a small green body of compacted powder particles is drawn over the surface in a well controlled multi pass linear reciprocating sliding contact. The capability of the test method was evaluated for different types of tool materials including two PVD coatings in contact with different types of metal powders to determine the friction characteristics and the adhesion and material transfer tendency at the sliding interface. Post-test examination of the tool surfaces using FEG-SEM and EDS were performed in order to evaluate the mechanisms controlling the friction behavior and the material transfer tendency. The results show that the proposed test is a simple and fast method to obtain relevant data regarding the friction and galling characteristics of die tool materials in metal powder compaction. The mechanisms prevailing at the green body/die tool material interface, e.g. cold welding, can easily be monitored by the friction and acoustic emission signals. Of the die tool materials investigated the low friction PVD a-C:Cr coating displayed the lowest friction and highest galling resistance.

  • 224.
    Olsson, Mikael
    Dalarna University, School of Information and Engineering, Materials Technology.
    Characterization of hot-rolled and annealed oxides on 2507 stainless steel – Microstructure, chemical composition, mechanical properties and pickling characteristics2021Report (Other academic)
    Abstract [en]

    The surface characteristics of samples of the 2507 super duplex stainless steel with three different surface conditions, i.e. after hot rolling, annealing and blasting plus pickling, respectively, have been investigated. High resolution scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and scratch testing have been used to characterize the oxide scales with respect microstructure, chemical composition, and mechanical properties.

    SEM and EDS-analysis of the oxide scales formed on hot rolled and hot rolled plus annealed samples, show an outer Fe-rich oxide layer and an inner Cr-rich oxide layer close to the interface. While the hot rolled oxide scale displays a relatively porous oxide composed of oxide particles, the hot rolled plus annealed oxide scale displays a more dense, “sintered”, microstructure, i.e. the high temperature during the annealing step promotes a densification of the oxide scale microstructure.

    The outer porous Fe-rich layer shows poor cohesive strength and poor adhesion to the underlying Cr-rich layer. In contrast, the inner more dense Cr-rich layer shows strong adhesion towards the 2507 duplex stainless steel. The dense microstructure and strong adhesion of the inner Cr-rich layer is believed to significantly influence the blasting and pickling characteristics.

  • 225.
    Olsson, Mikael
    Dalarna University, School of Information and Engineering, Materials Technology.
    Characterization of oxide layers formed on pilot plant Steckel rolled 304 stainless steel samples2021Report (Other academic)
    Abstract [en]

    The evolution of oxide scales on 304 austentic stainless steel during Steckel mill rolling has been investigated by performing pilot trials at Swerim Luleå. The influence of Steckel furnace conditions, i.e. temperature, time and excess oxygen, at reheating between subsequent roll passes have been evaluated and the resulting surface structures have been characterized.

    High resolution scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to characterize the oxide scales with respect microstructure and chemical composition. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to analyze the chemical composition at the stainless steel / oxide interface region.

    In common for all Steckell rolled samples investigated was a pronounced rough surface morphology and the surface roughness was found to increase with more iterations of rolling. Also, the amount of oxides in the rolled surface tends to increase with longer heating times and more iterations of rolling. 

    Surface areas, less distorted by the rolling contact, displayed an oxide scale with an outer rather well-defined oxide layer with relatively large grains and an inner, less well defined, oxide layer. EDS-analysis show that the outer oxide mainly consists of Fe2O3, whereas the inner oxide layer corresponds to a chromium rich (Cr,Fe)2O3 oxide combined with areas of partly oxidized stainless steel. ToF-SIMS analysis of the stainless steel / oxide interface region show the presence of B, Ca and Cu in connection to the oxides.

  • 226.
    Olsson, Mikael
    Dalarna University, School of Information and Engineering, Materials Technology.
    Influence of annealing on hot-rolled oxides on 2507 stainless steel2021Report (Other academic)
    Abstract [en]

    The influence of annealing on the oxide scale characteristics of hot rolled samples of 2507 super duplex stainless steel have been investigated using well controlled lab scale annealing experiments. High resolution scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to characterize the oxide scales with respect microstructure and chemical composition.

    SEM and EDS-analysis of the oxide scales after annealing show an outer Fe-rich oxide layer and an inner Cr-rich oxide layer close to the interface. While the hot rolled oxide scale displays a relatively porous oxide composed of oxide particles, the hot rolled plus annealed oxide scale displays a more dense, “sintered”, microstructure.

    The annealing peak temperature was found to have a strong impact on the oxide scale microstructure. The higher peak temperature, 1150 °C, resulted in a significantly denser microstructure with more pronounce, larger grains, as compared with the lower peak temperature, 1100 °C, which resulted in a less dense microstructure. In contrast, the influence of annealing atmosphere, was found to be relatively small.

  • 227.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    On the use of scratch testing as a model experiment for evaluating the initial wear of cemented carbidein rock drilling2013Conference paper (Refereed)
  • 228.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Tribologi i samband med pulverkompaktering2011In: Stålforskningsdagar 2011 : materialteknik vid Högskolan Dalarna / [ed] Storck, Joakim, Borlänge, 2011Conference paper (Other academic)
  • 229.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Tribological evaluation of some potential tribo materials used in column lift rolling contacts: a case study2011In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 270, no 9-10, p. 720-724Article in journal (Refereed)
    Abstract [en]

    The friction and wear characteristics of some potential tribological pairs aimed for the wheel/rail rolling contact in column lifts were studied. Tribo tests were performed using a pin-on-disc equipment and the tribological pairs included; stainless steel against ball bearing steel, stainless steel against WC/C-coated ball bearing steel and stainless steel against cast nylon (polyamide 6). The influence of coating surface topography as well as stainless steel surface topography on the friction and wear behaviour of the tribological pairs was investigated. The results show that the WC/C-coating significantly improves the tribological performance of the stainless steel/ball bearing steel sliding couples but that the WC/C-coating show a limited life-time in sliding contact with stainless steel under the prevailing contact conditions. In contrast, the stainless steel/ball bearing steel sliding couples suffer from high friction and wear due to strong adhesion between the mating surfaces followed by metal transfer and severe adhesive wear. The stainless steel/cast nylon sliding couples show a somewhat intermediate behaviour regarding friction and wear where the friction is controlled by the generation of a polymer transfer film and wear of the cast nylon is controlled by the surface topography of the mating stainless steel surface. The results obtained are discussed in relation to the identified friction and wear mechanisms as characterized by SEM and EDX.

  • 230.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Tråddragningens tribologi2015In: Nordisk Trådteknisk Förening: Årsbok 2015 / [ed] Leif Eriksson, NTTF , 2015Chapter in book (Other academic)
  • 231.
    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.

  • 232.
    Olsson, Mikael
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Heinrichs, Jannica
    Yvell, Karin
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jacobson, Staffan
    Initial degradation of cemented carbides for rock drilling: model studies of the tribological contact against rock2015In: International journal of refractory metals & hard materials, ISSN 0263-4368, Vol. 52, p. 104-113Article in journal (Refereed)
    Abstract [en]

    Hardness and fracture toughness are often used as the prime material parameters to characterise cemented carbides used in rock drilling. However, the deformation and wear of cemented carbide are too complicated to be described by these parameters alone. The cemented carbide and the wearing rock mineral are both composite materials, containing phases with widely varying hardness. Moreover, the deformation behaviour of the individual phases may be strongly anisotropic, as for the WC grains in the cemented carbide. The wear of the cemented carbide typically occurs on the scale of individual grains or smaller. Contrastingly, the hardness stated for both is typically a macroscopic value, averaged over numerous grains, orientations, etc. The present investigation aims to contribute to the understanding of the relations between microstructure, properties and wear mechanisms of cemented carbide buttons in rock drilling. It is focused on the role of scale of deformation in relation to size of the different phases of the cemented carbide. This is achieved by simplifying the contact situation of the rock drill button to a single stylus sliding contact between a granite stylus and a polished cemented carbide surface. The deformation and wear of this well controlled contact is then evaluated on the sub-micrometer scale; using high resolution FEG-SEM with EBSD, FIB cross-sectioning and AFM. The results show that even an extremely local deformation, such as slip within individual WC grains, affects the tribological contact, and that the nominally much softer granite may cause deformation both within individual WC grains, and on the composite scale. The results are discussed with respect to their significance for wear of cemented carbides in rock drilling. (C) 2015 Elsevier Ltd. All rights reserved.

  • 233.
    Olsson, Mikael
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Högman, B
    Uddeholms.
    Influence of tool steel microstructure on the prevailing wear mechanisms in metal powder compaction2012In: TOOL 2012 : proceedings of the 9th international tooling conference, developing the world of tooling, Montanuniversität Leoben 11-14 September 2012 / [ed] Herald Leitner, Regina Kranz, Angelika Tremmel, Knittelfeld: Gutenberghaus , 2012, p. 409-416Conference paper (Refereed)
  • 234.
    Olsson, Mikael
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Karlsson, P.
    Eriksson, Jenny
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Gåård, A.
    Krakhmalev, P.
    Bergström, J.
    Galling resistance evaluation of tool steels by two different laboratory test methods for sheet metal forming2011In: Proceedings of the 18th International Conference on Wear of Materials, Philadelphia, USA, 2011Conference paper (Other academic)
  • 235.
    Olsson, Mikael
    et al.
    Dalarna University, School of Information and Engineering, Materials Technology.
    Lundin, Peter
    Swerim.
    Samuelsson, Jan-Erik
    Erasteel Kloster.
    Tjerngren, Peter
    SMT/Alleima.
    Åhlberg, Richard
    Fagersta Stainless.
    Börjesson, Malin
    Kanthal.
    Balazs, Emil
    Ovako.
    Färre ytfel på varmvalsade produkter2022Report (Other academic)
  • 236.
    Olsson, Mikael
    et al.
    Dalarna University, School of Information and Engineering, Materials Technology.
    Lundin, Peter
    Swerim.
    Samuelsson, Jan-Erik
    Erasteel Kloster.
    Tjerngren, Peter
    SMT/Alleima.
    Åhlberg, Richard
    Fagersta Stainless.
    Börjesson, Malin
    Kanthal.
    Balazs, Emil
    Ovako.
    YTFEL Deelrapport - Verksförsök2022Report (Other academic)
  • 237.
    Olsson, Mikael
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Sandberg, Odd
    Tribological evaluation of tool materials for powder compaction2010In: Proceedings of the World Powder Metallurgy Congress and Exhibition, World PM 2010, Florence, 2010, Vol. 5Conference paper (Refereed)
    Abstract [en]

    The friction characteristics and material transfer tendency between metal powder and tool material in metal powder compaction have been evaluated using a new tribo test method. The method is based on controlled scratch testing using a commercial scratch tester but instead of the commonly used Rockwell C diamond stylus a sample holder with a small green body of compacted powder particles is drawn over the surface in a well controlled multi pass linear reciprocating sliding contact. In the present study a number of combinations of metal powder and tool materials have been evaluated with respect to the friction characteristics and the sticking and cladding tendency at the sliding interface. Post test scanning electron microscopy and energy dispersive X-ray spectroscopy in combination with 3D white light interferometry were used to analyse the tool material surfaces and material pick-up tendency. The tribological performance of potential powder compacting tool materials is discussed in relation to the identified friction and wear mechanisms.

  • 238.
    Olsson, Mikael
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Surreddi, Kumar Babu
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Scratch testing of cemented carbides - Influence of Co binder phase and WC grain size on surface deformation and degradation mechanisms2018In: Proceedings of The 18th Nordic Symposium on Tribology - Nordtrib 2018 / [ed] Staffan Jacobson, Uppsala: Uppsala University, 2018Conference paper (Refereed)
    Abstract [en]

    In the present study, the microstructural response of some commercial cemented carbide grades during scratchinghas been analyzed and evaluated by a number of post-test characterization techniques. The influence of Co binder phase content and WC grain size on the deformation and degradation on a WC grain size scale and on a composite scaleare evaluated. The results clearly illustrate the complexity of deformation, degradation and wear of cemented carbide and the dynamics of the diamond stylus / cemented carbide contact during the scratching event. For all cementedcarbide grades the microstructure has a strong impact on the observed degradation mechanisms and the resistance to deformation and degradation was found to increase with decreasing Co content and decreasing WC grain size.

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  • 239.
    Olsson, Mikael
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Surreddi, Kumar Babu
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Thin hard CVD and PVD coatings and their potential in steel wire drawing applications2018In: Proceedings of The 18th Nordic Symposium on Tribology - NORDTRIB 2018 / [ed] Staffan Jacobson, Uppsala: Uppsala University, 2018Conference paper (Refereed)
    Abstract [en]

    In the present work, the potential of using thin hard CVD and PVD coatings in order to improve the performance of cemented carbide steel wire drawing nibs is evaluated. Coating materials include some state-of-the-art CVD and PVD coatings and pre- and post-coating treatments were used to improve the surface topography of the coated functional surfaces. The tribological performance of the coatings has been evaluated by sliding wear tests and wire drawing experiments under well controlled conditions. Post-test characterization of the coated nibs using 3D optical surface profilometry, scanning electron microscopy and energy dispersive X-ray spectroscopy illustrates the pros and cons of the two deposition techniques but also that the coatings have a potential to improve the performance of cemented carbide nibs in steel wire drawing applications.

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    fulltext
  • 240.
    Olsson, Mikael
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Wadman, B.
    Eriksson, Jenny
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Schedin, E.
    Madsen, E.
    Bay, N.
    Influence of stainless steel surface texture on galling2011In: Proceedings of the 18th International Conference on Wear of Materials, Philadelphia, USA, 2011Conference paper (Other academic)
  • 241.
    Olsson, Mikael
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology. Ångström Tribomaterials Group, Uppsala University.
    Yvell, Karin
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Heinrichs, J.
    Bengtsson, M.
    Jacobson, S.
    Surface degradation mechanisms of cemented carbide drill buttons in iron ore rock drilling2017In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 388-389, p. 81-92Article in journal (Refereed)
    Abstract [en]

    The wear behavior of cemented carbide rock drill buttons is influenced by many factors, which include the composition and microstructure of the cemented carbide material, the nature of the rock material, and the conditions of the rock drilling operation. Depending on the type of rock and on the drilling procedure used, the cemented carbide is exposed to substantially differing mechanical and thermal conditions. In the present study, the surface degradation and wear mechanisms of cemented carbide drill buttons exposed to iron ore rock drilling have been characterized based on a combination of high resolution scanning electron microscopy (SEM), focused ion beam cross-sectioning (FIB), energy-dispersive X-ray spectroscopy (EDS) and electron back scatter diffraction (EBSD).The results show a significant difference in surface degradation and wear between the front and peripheral buttons of the drill bits. While the front buttons display a relatively smooth worn surface with shallow surface craters the peripheral buttons display a reptile skin pattern, i.e. plateaus, 200-300. μm in diameter, separated by valleys, typically 40-50. μm wide and 15-30. μm deep, The reptile skin pattern is obtained in regions where the peripheral buttons are in sliding contact against the drill hole walls and exposed to high surface temperatures caused by the frictional heating. The results indicate that the reptile skin pattern is related to friction induced thermal stresses rather than mechanical contact stresses, i.e. the reptile skin pattern is formed due to thermal fatigue, rather than mechanical fatigue, caused by the cyclic frictional heating generated at the cemented carbide button/iron ore interface.

  • 242.
    Olsson, Mikael
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Yvell, Karin
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Heinrichs, Jannica
    Uppsala University.
    Bengtsson, Maria
    LKAB Wassara AB.
    Jacobson, Staffan
    Uppsala University.
    Surface degradation mechanisms of cemented carbide drill buttons exposed to iron ore rock drilling2016In: Proceedings of the 17th Nordic Symposium on Tribology - Nordtrib 2016, 2016Conference paper (Refereed)
    Abstract [en]

    The wear behavior of cemented carbide rock drill buttons is influenced by many factors, which include the composition and microstructure of the cemented carbide material, plus the conditions of the rock drilling operation, such as drilling parameters, drill button geometry and the nature of the rock material. Depending on the type of rock and on the drilling procedure used, the cemented carbide is exposed to substantially differing mechanical and thermal conditions. Under conditions of high mechanical stress and high temperatures, typical for drilling in highly abrasive rocks such as granite, the worn cemented carbide buttons are usually very smooth, with the roughness limited to within the size of individual WC grains. When drilling under conditions of moderate mechanical stress and high temperatures, typical for drilling in low-abrasive rock, such as ores with e.g. magnetite, the surface damage of the buttons usually includes a macroscopic surface wear pattern, commonly referred to as “reptile skin”, in an otherwise smooth surface. The crack growth associated to the valleys of the reptile skin pattern eventually leads to catastrophic fracture of the button, unless the cracked surface layer is repeatedly ground off before the cracks grow too deep. So despite the low general wear rate, the wear life of drill buttons becomes severely restricted by the surface cracks. The present study focuses on revealing the degradation mechanisms behind the formation of the reptile skin. This is done by analyzing drill buttons exposed to different stages of degradation and wear from drilling in iron ore. The work is based on a combination of high resolution scanning electron microscopy (SEM), focused ion beam microscopy (FIB), energy-dispersive X-ray spectroscopy (EDS) and electron back scatter diffraction (EBSD).

  • 243.
    Olsson, Mikael
    et al.
    Dalarna University, School of Information and Engineering, Materials Technology.
    Åhlberg, Richard
    Fagersta Stainless.
    YTFEL Delrapport - Ytfelsatlas2022Report (Other academic)
  • 244.
    Osterman, Jesper
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Tong, Au Ping
    Zhukov, Andrey
    Chigrinov, Vladimir
    Kwok, Hoi Sing
    Mechanically stabilized bistable FLC cells on plastic substrates2005In: Proceedings of the twenty-fifth international display research conference, Eurodisplay 2005, 2005Conference paper (Refereed)
    Abstract [en]

    The electro-optical properties of a full v flexible photo-aligned FLC cell are investigated. Two different methods, sticky spacers together with a photo-sensitive monomer and polymer spacers in a regular pattern formed by photo-lithography, are proposed to stabilize the structure in order to increase the bending tolerance of the FLC material during deformation of the cell.

  • 245.
    Osterman, Jesper
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Tong, Au Ping
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Chigrinov, Vladimir
    Kwok, Hoi Sing
    Properties of azo-dye alignment layer on plastic substrates2005In: Journal of the Society for Information Display, ISSN 1071-0922, E-ISSN 1938-3657, Vol. 13, no 12, p. 1003-1009Article in journal (Refereed)
    Abstract [en]

    The alignment properties of the azo dye photo-alignment material SD-1/SDA-2 on plastic substrates are investigated. Excellent alignment with high anchoring energy can be achieved with a polarized UV dose less than 1.0 J/cm2. A reflective 6-digit flexible passive matrix driven TN-LCD for smart card applications showing excellent electro-optical properties is demonstrated.

  • 246. Park, J. M.
    et al.
    Jayamani, Jayaraj
    Kim, D. H.
    Mattern, N.
    Wang, G.
    Eckert, J.
    Tailoring of in situ Ti-based bulk glassy matrix composites with high mechanical performance2010In: Intermetallics (Barking), ISSN 0966-9795, E-ISSN 1879-0216, Vol. 18, no 10, p. 1908-1911Article in journal (Refereed)
    Abstract [en]

    In this study, we developed ductile dendrite-reinforced composites in the Ti–Zr–Ni–Cu–Be–(Nb) system. Although in situ composites have been successfully obtained by optimizing alloy composition and cooling rate, plasticity does not always occur. Only when the size, distribution, and elastic constants of the constituent phases are properly controlled, i.e. by creating homogeneously distributed dendrites with lower shear modulus than the glassy matrix, the composites exhibit large plasticity. By controlling the microstructural length scale and by tuning the intrinsic elastic constants of the constituent phases Ti-based bulk glassy matrix composites with good mechanical performance (high yield strength of ∼1.7GPa and large plasticity of ∼25%) have been achieved.

  • 247.
    Persson, Petter
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Finite element analysis of hot rolling in the blooming mill2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 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.

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  • 248.
    Persson, Petter
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Mätsystemanalys av mätmetod för kontroll av anoljningsgrad2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    At the end of the continuous annealing line at SSAB´s production plant in Borlänge a large portion of the produced sheet metal is oiled. Oiling of sheet metal is performed when a higher corrosion resistance is desirable, for example during transportation in a ship where it is exposed to a corrosive environment. To ensure that the correct amount of oil is applied, a visual inspection is done three times a day and each time the degree of oiling is changed. In addition, controls are done six times a year with a consumption measuring device. 

    The purpose of this thesis is to evaluate the current measurement method and to consider its use in the future. Possible improvements of this method are sought. Also, an oil thickness sensor is evaluated as an alternative.

    Three different measurement methods are used during the work with this thesis and a measurement systems analysis is carried out. This is done by compiling data in the statistical software Minitab 16 and the results were interpreted with regards to accuracy and precision.

    The results show that the consumption measuring device delivers more stable values than the oil thickness sensor when used during production. This is due to the sensors small measurement area and the drop-like way the oiling device applies oil. 

  • 249.
    Pirouznia, Pouyan
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Andersson, N. A. I.
    Tilliander, A.
    Jonsson, P. G.
    A mathematical model of martempering of thin martensitic stainless steel strips2015In: Proceedings of the 6th International Congress on the Science and Technology of Steelmaking, ICS 2015, 2015, p. 1027-1030Conference paper (Refereed)
    Abstract [en]

    The martempering process produces thin martensitic stainless steel strips and is widely used for production of valve- and spring steel. Industrial trials were conducted in collaboration with Böhler Uddeholm Precision Strip, Munkfors, Sweden. These trials suggested that the quenching step is critical to control, in order to reduce uneven temperature gradients which will lead to distortions or unevenness. To investigate this, computational modelling of the temperature was performed to estimate the current situation for the conventional martempering process based on physical theories together with Comsol Multiphysics and using a steady state modeling approach. The model boundary conditions were based upon temperature measurements in the real process. Furthermore, the strip was modelled as it comes out of the heating furnace, which is filled with hydrogen gas and continues into a molten lead-bismuth bath for quenching. Thus, the temperature profile was obtained for the strip as well as its surroundings; The results show that a better insight of the martempering line could be achieved. The model results can be used to investigate disturbances in the normal operation. Furthermore, the temperature profiles can be used to optimize the process and possibly to reduce the energy consumption.

  • 250.
    Pirouznia, Pouyan
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology. KTH Royal Institute of Technology; voestalpine Precision Strip AB, Munkfors.
    Andersson, N. ÅI.
    Tilliander, A.
    Jönsson, P. G.
    The impact of the gas inlet position, flow rate, and strip velocity on the temperature distribution of a stainless-steel strips during the hardening process2019In: Metals, E-ISSN 2075-4701, Vol. 9, no 9, article id 928Article in journal (Refereed)
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