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  • 1.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Beläggningar till högtemperaturbränsleceller2011In: Stålforskningsdagarna 2011 / [ed] Joakim Storck, Borlänge: Högskolan Dalarna , 2011, p. 89-99Conference paper (Other academic)
    Abstract [sv]

    Det finns en tro om att framtida högtemperaturbränslecellssystem kommer att ha en arbetstemperatur i intervallet 700-850°C. Vid dessa temperaturer kan man utnyttja metalliska material som bipolära plattor i en bränslecellsstack. Det har utvecklats speciella legeringar i just detta syfte men för ytterligare öka på prestandan måste dessa legeringar beläggas med lämpliga föreningar. Syftet med denna artikel är att visa att man kan förbättra olika egenskaperna av ett ferritiskt rostfritt stål genom att belägga det med lämpliga metalliska skikt.

  • 2.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Time-of-Flight SIMS Characterization of Hydrolysed Organofunctional and Non-Organofunctional Silanes Deposited on Al, Zn and Al-43.4Zn-1.6Si Alloy-Coated Steel2003In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 35, no 11, p. 880-887Article in journal (Refereed)
  • 3.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Jani, Simon
    AB Sandvik Materials Technology, Sandviken, Sweden.
    Lundberg, Mats W.
    AB Sandvik Materials Technology, Sandviken, Sweden.
    Initial oxidation of ferritic interconnect steel, effect due to a thin ceria coating2012In: European Fuel Cell Forum 2012 - Proceedings (memory stick), 2012Conference paper (Other academic)
    Abstract [en]

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

  • 4. Canovic, Sead
    et al.
    Engkvist, Josefin
    Dalarna University, School of Technology and Business Studies, Material Science.
    Liu, Fang
    Götlind, Helena
    Hellström, Kristina
    Svensson, Jan-Erik
    Johansson, Lars-Gunnar
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Halvarsson, Mats
    Microstructural investigation of the initial oxidation of the FeCrAlRE alloy Kanthal AF in dry and wet O2 at 600 and 800°C2010In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 157, no 6, p. C223-C230Article in journal (Refereed)
    Abstract [en]

    The FeCrAlRE (where RE is reactive element) alloy Kanthal AF was exposed isothermally at 600 and 800°C for 72 h in dry O2 and in O2 with 10 vol % H2O. The mass gains were 3–5 times higher at the higher temperature. The presence of water vapor increased the oxidation rate at 800°C, while no significant effect was observed at 600°C. A thin two-layered oxide formed at 600°C: an outer (Fe,Cr)2O3 corundum-type oxide, containing some Al, and an inner, probably amorphous, Al-rich oxide. At 800°C a two-layered oxide formed in both environments. The inner layer consisted of inward grown a-Al2O3. In dry O2 the originally formed outward grown g-Al2O3 had transformed to a-Al2O3 after 72 h. Water vapor stabilized the outward grown g-Al2O3 and hence no transformation occurred after 72 h in humid environment. RE-rich oxide particles with varying composition (Y, Zr, and Ti) were distributed in the base oxide at both temperatures and in both environments. The RE-rich particles were separated from the alloy substrate by a layer of Al-rich oxide. At 800°C the Y-rich RE particles were surrounded by thick oxide patches in both dry and humid O2.

  • 5. Engkvist, Josefin
    Characterization of oxide scales formed on FeCrAl alloys at high temperatures2009Doctoral thesis, monograph (Other academic)
    Abstract [un]

    This thesis focuses on the characterization of oxide scales formed on FeCrAl alloys at high temperatures. The effect of water vapour on commercial FeCrAl alloys oxidized in both dry and humid O2 has been investigated. Also, the effect of varying Al concentrations in model FeCrAl alloys was studied as well as the effect of using surface coatings in order to increase the oxidation resistance of FeCrAl alloys. The formed oxide scales were characterized using analysis techniques such as SEM, EDX, TEM, XRD, XPS, AES and SIMS. The main part of the work concerns the SEM, EDX, AES and SIMS techniques. The commercial FeCrAl alloys investigated follow the same trend in oxide formation independent of whether the alloy was conventionally cast or manufactured by powder metallurgy. In the as-received cold rolled condition the surface of the FeCrAl material shows a few nm thin native oxide. This native oxide is a mixture of oxides from Fe, Cr and Al, with a relatively high concentration of Cr. The oxide formation at elevated temperatures can be separated in a low temperature and a high temperature mode. At relatively low temperatures (500-600°C) a mixed oxide similar to the pre-existing native oxide forms, while at higher temperatures a thicker two-layered alumina scale forms. The outer and inner alumina layers are separated by a Cr-rich zone which is believed to be a remnant of the pre-existing native oxide and hence represents the original alloy surface. Accordingly the inner alumina layer is formed by oxygen inward diffusion while the outer alumina layer grows by cation outward diffusion. The inner alumina is composed of a-Al2O3, while the outer layer, during early stages, is composed of rapidly growing metastable polymorphs of alumina which with time transform to a-Al2O3. This phase transformation starts at the Cr-rich zone and progress outward. In presence of water vapour this transformation is inhibited due to hydroxylation of the surface of the metastable phases. Hence, a higher oxidation rate was observed in presence of water vapour. Model FeCrAl alloys having Al concentrations in the range 1.2-5 wt.% were investigated. At 900°C a minimum of 3.2% Al is needed in order to form a continuous alumina scale. Higher Al concentrations (= 4.4%) result in a relatively pure alumina scale and a slower oxidation rate. In order to evaluate the possibility to improve the oxidation resistance of FeCrAl a PVD SiO2 coating was applied on a commercial FeCrAl foil prior to oxidation. Parallel exposures of coated and uncoated samples were made at 1000°C and revealed that the SiO2 coating significantly reduced the initial oxidation rate of the FeCrAl foil. Further, metal organic CVD of a ZrO2 film in situ on an RE free FeCrAl alloy at 400 and 800°C showed that at the lower temperature mainly ZrO2 was formed while at 800°C an oxide scale composed of both ZrO2 and Al2O3 was formed. The results obtained illuminate the importance of advanced electron microscopy and surface analysis techniques in order to increase the understanding of high temperature oxidation of FeCrAl alloys and the oxidation mechanisms of this group of materials.

  • 6.
    Engkvist, Josefin
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Grehk, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    High temperature oxidation of FeCrAl-alloys: influence of Al-concentration on oxide layer characteristics2009In: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176, Vol. 60, no 11, p. 876-881Article in journal (Refereed)
    Abstract [en]

    The superior high temperature oxidation resistance of FeCrAl alloys relies on the formation of a dense and continuous protective aluminium oxide layer on the alloy surface when exposed to high temperatures. Consequently, the aluminium content, i.e. the aluminium concentration at the alloy–oxide layer interface, must exceed a critical level in order to form a protective alumina layer. In the present study the oxidation behaviour of six different FeCrAl alloys with Al concentrations in the range of 1.2–5.0wt% have been characterised after oxidation at 900 8C for 72 h with respect to oxide layer surface morphology, thickness and composition using scanning electron microscopy, energy dispersive X-ray spectroscopy and Auger electron spectroscopy.The results show that a minimum of 3.2wt% Al in the FeCrAl alloy is necessary for the formation of a continuous alumina layer. For Al concentrations in the range of 2.0–3.0wt% a three-layered oxide layer is formed, i.e. an oxide layer consisting of an inner alumina-based layer, an intermediate chromia-based layer and an outer iron oxide-based layer. In contrast, the 1.2wt% Al FeCrAl alloy is not able to form a protective oxide layer inhibiting extensive oxidation.

  • 7.
    Engkvist, Josefin
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Canovic, Sead
    Liu, Fang
    Götlind, Helena
    Svensson, Jan-Erik
    Johansson, Lars-Gunnar
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Halvarsson, Mats
    Oxidation of FeCrAl foils at 500-900 C in dry O2 and O2 with 40% H2O2009In: 7th Int. Conf. on the Microscopy of Oxidation, Chester, UK, 2009Conference paper (Other academic)
  • 8.
    Engkvist, Josefin
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Grehk, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Early stages of oxidation of uncoated and PVD SiO2 coated FeCrAl foils2009In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 203, no 19, p. 2845-2850Article in journal (Refereed)
    Abstract [en]

    The high temperature oxidation characteristics of uncoated and SiO2 PVD-coated FeCrAl foils have been investigated when exposed to laboratory air at 1000 °C during 1, 2, 4, 8, 16, 32 and 60 min. The oxidized samples were characterized using SEM, EDS, AES and SIMS. The results show that the presence of a 100 nm thin SiO2 PVD coating significantly reduces the oxidation rate of the FeCrAl foil during early stages of oxidation. The decreased oxidation rate displayed by the SiO2 coated FeCrAl foil is the result of the SiO2 coating acting as an initial diffusion barrier promoting the formation of a predominantly inward growing Al2O3 layer during oxidation. Additionally, by using EDS analysis together with AES and SIMS depth profiling it was shown that the total concentration of Si in the grown oxide scale decreased during oxidation.

  • 9.
    Eriksson, Jenny
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Tribological testing of commercial CrN, (Ti,Al)N and CrC/C PVD coatings: evaluation of galling and wear characteristics against different high strength steels2011In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 205, no 16, p. 4045-4051Article in journal (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 of galling in sheet 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 potential performance of three commercial PVD coatings, including CrN, (Ti,Al)N and a CrC/C DLC-based coating, in the forming of hot and cold rolled high strength steel as well as electro and hot-dip galvanized high strength steel has been evaluated using pin-on-disc testing under lubricated contact conditions. Post-test examination of the tribosurfaces using FEG-SEM and EDS analyses was performed in order to evaluate the mechanisms controlling the tendency to material transfer and wear. The results show that in contact with the hot and cold rolled steel the material pick-up tendency of the PVD coatings tend to increase in the order CrC/C–CrN–(Ti,Al)N while in contact with the two galvanized steel sheets, the CrC/C and the (Ti,Al)N coating show a significantly lower material pick-up tendency as compared with the CrN coating. Further, the substrate hardness has a strong influence on the wear of the PVD coatings and consequently on the friction characteristics and galling tendency of the coating/substrate composite. Low substrate hardness, resulting in a low load bearing capacity, increases the tendency to cracking and subsequently chipping of the brittle coating.

  • 10.
    Fallqvist, Mikael
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    M’Sauobi, R
    Seco Tools.
    Andersson, J
    Seco Tools.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Mechanical and tribological properties of PVD-coated cemented carbide as evaluated by a new multi-pass scratch testing method2012In: Advances in Tribology, ISSN 1687-5915, E-ISSN 1687-5923, no 305209Article in journal (Refereed)
    Abstract [en]

    A new test method based on multipass scratch testing has been developed for evaluating the mechanical and tribological properties of thin, hard coatings. The proposed test method uses a pin-on-disc tribometer and during testing a Rockwell C diamond stylus is used as the “pin” and loaded against the rotating coated sample. The influence of normal load on the number of cycles to coating damage is investigated and the resulting coating damage mechanisms are evaluated by posttest scanning electron microscopy. The present study presents the test method by evaluating the performance of Ti0.86Si0.14N, Ti0.34Al0.66N, and (Al0.7Cr0.3)2O3 coatings deposited by cathodic arc evaporation on cemented carbide inserts. The results show that the test method is quick, simple, and reproducible and can preferably be used to obtain relevant data concerning the fatigue, wear, chipping, and spalling characteristics of different coating-substrate composites. The test method can be used as a virtually nondestructive test and, for example, be used to evaluate the fatigue and wear resistance as well as the cohesive and adhesive interfacial strength of coated cemented carbide inserts prior to cutting tests.

  • 11.
    Fallqvist, Mikael
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    The influence of surface defects on the mechanical and tribological properties of VN-based arc-evaporated coatings2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 297, no 1-2, p. 1111-1119Article in journal (Refereed)
    Abstract [en]

    The influence of surface defects, i.e., droplets and craters, on the mechanical and tribological properties of arc-evaporated VxN coatings deposited on cemented carbide has been investigated in a scratching contact using a diamond stylus and a sliding contact using a stainless steel pin. Post-test characterisation using 3D optical surface profilometry and scanning electron microscopy was performed in order to investigate the mechanical and tribological response of the coatings. The results show that scratch induced coating cracking mainly is restricted to larger droplets showing a low interfacial bonding to the adjacent coating matrix. The influence of coating defects on the cohesive strength, i.e., the tendency to chipping of small coating fragments, was found to be relatively small. In contrast, the presence of defects may have a significant impact on the interfacial adhesive strength, increasing the tendency to spalling. In sliding contact, surface defects such as droplets and craters have a strong impact on the tribological behaviour of the coatings causing abrasive wear of the less hard counter material surface and material transfer to the coating, both mechanisms affecting the friction characteristics of sliding contact tribo systems.

  • 12.
    Fallqvist, Mikael
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Ruppi, S
    Seco Tools.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Ottosson, M
    Uppsala Universitet.
    Grehk, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology. Sandvik Materials Technology.
    Nucleation and growth of CVD α-Al2O3on TixOy template2012In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 207, p. 254-261Article in journal (Refereed)
    Abstract [en]

    The microstructure, phase and chemical composition of TixOy templates used to nucleate α-Al2O3 on Ti(C,N) coated cemented carbide have been elucidated using scanning electron microscopy, X-ray diffraction, Auger electron spectroscopy and Time-of-Flight Secondary Ion Mass Spectrometry. Further, the adhesive strength of the α-Al2O3–TixOy–Ti(C,N) interfaces was investigated using scratch adhesion testing.

    The present study confirmed that the as-deposited template consisted of a Ti4O7 phase which during subsequent deposition of the Al2O3 layer transformed to a Ti3O5 phase and that the grown Al2O3 layer consisted of 100% α-Al2O3. Furthermore, the results showed that the lowest interfacial strength within the multilayer structure was exhibited by the Ti(C,N)–TixOy interface and that the transformation of Ti4O7 to Ti3O5 in the template resulted in formation of pores in the Ti(C,N)-template interface lowering the interfacial strength even more. The use of surface analysis techniques such as Auger electron spectroscopy and especially Time-of-Flight Secondary Ion Mass Spectrometry enabled trace element analyses using depth profiling to characterise the thin interfacial layers in detail.

  • 13.
    Fallqvist, Mikael
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Schultheiss, F
    Lunds Universitet.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    M’Sauobi, R
    Seco Tools.
    Ståhl, J E
    Lunds Universitet.
    Influence of CVD Al2O3 coated tool surface micro topography on the tribological characteristics in metal cutting: part I2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, p. 87-98Article in journal (Refereed)
    Abstract [en]

    The influence of surface micro topography of CVD α-Al2O3 coatings, deposited on cemented carbide inserts, on tribological characteristics in sliding contact and in metal cutting has been investigated using quenched and tempered steel as counter/work material. Pin-on-disc and turning tests were carried out and post-test characterization using 3D optical surface profilometry and scanning electron microscopy was performed in order to investigate the tribological response of the coatings. The results show that surface micro topography can have a significant impact on the tribological performance of Al2O3 coatings under initial and cutting contact conditions. For both kinds of tests the tendency for transfer of workpiece material strongly increases with increasing coating micro topography. In the pin-on-disc tests, a smooth coating surface significantly reduces the friction coefficient. In the turning tests the contact conditions at the flank face increase with decreasing micro topography. In contrast, no general conclusions can be drawn regarding the influence of coating micro topography on the contact conditions at the rake face. The resulting topography of the turned surface was found to increase with increasing coating topography.

  • 14. Harfouche, Sara
    et al.
    Padam, Benita
    Dimensionsmätning av varma ämnen i LIMAB och undersökning av krympfaktorer2014Independent 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.

     

  • 15.
    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.

  • 16.
    Harlin, Peter
    et al.
    Sandvik Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Abrasive wear resistance of starch consolidated and sintered high speed steel2009In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 267, no 9-10, p. 1482-1489Article in journal (Refereed)
    Abstract [en]

    The abrasive wear resistance of starch consolidated (SC) and super solidus liquid phase sintered (SLPS) M3/2 high speed steel (HSS) samples have been evaluated by a two-body micro-abrasion test (low stress abrasion), using 6 µm diamond abrasive particles, and a three-body abrasion test (high stress abrasion), using significantly larger abrasive particles of blast furnace slag (600 HV) and silicon carbide (2400 HV), respectively. In the tests a commercial powder metallurgical (PM) HSS was used as a reference material. The results show that the microstructure of the SC and SLPS HSS samples is strongly dependent on the sintering temperature used. With increasing temperature the microstructure ranges from a porous (5% porosity) relatively fine grained low temperature sintered microstructure to a fully dense relatively coarse grained high temperature sintered microstructure with eutectic carbides/carbide networks. However, despite the pronounced microstructural differences displayed by the as-sintered HSS microstructures these show a relatively high abrasive wear resistance, comparable with that of a HIPed HSS reference, both under low and high stress abrasion contact conditions. The characteristic features of the low and high temperature sintered microstructures, i.e. the pores and coarse eutectic carbides/carbide networks, only show a limited impact on the wear rate and the wear mode (dominant wear mechanism). The results obtained imply that near net shaped components manufactured by starch consolidation and super solidus liquid phase sintering might be of interest in tribological applications.

  • 17.
    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.

  • 18.
    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)
  • 19.
    Heinrichs, J
    et al.
    Uppsala Universitet.
    Olsson, Mikael
    Jacobson, S
    Uppsala Universitet.
    Initiation of Galling in Metal Forming: Differences Between Aluminium and Austenitic Stainless Steel Studied In Situ in the SEM2013In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 50, no 3, p. 431-438Article in journal (Refereed)
    Abstract [en]

    High friction and transfer of work material to tool surfaces constitute important industrial problems in forming of many metals and alloys. However, it is very hard to gain a deeper understanding of these phenomena by studying real forming operations. In this paper, we have tried to gain fundamental understanding by avoiding as much as possible of the complexity of real forming. This has been realised by studying the friction and material transfer between well-defined tool material surfaces; uncoated and DLC-coated tool steel, and a needle shaped austenitic stainless steel tip, in situ in the SEM. The tool materials were tested in two conditions; well polished and well polished with local intentional scratches. It was found that work material was immediately transferred to the tool steel surface. When passing an intentional scratch, the local transfer was on a much larger scale, and the friction was higher, but the effect was mostly local. For the polished DLC-coated surface, almost no work material was transferred and the friction was low. An intentional scratch in the polished DLC surface barely influenced the galling behaviour. The present results are discussed in the light of previously published results from an analogous study with aluminium as work material.

  • 20.
    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)
  • 21.
    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.

  • 22.
    Lindgren, Michael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Experimental and computational investigation of the roll forming process2009Doctoral thesis, monograph (Other academic)
    Abstract [en]

    One of the first questions to consider when designing a new roll forming line is the number of forming steps required to produce a profile. The number depends on material properties, the cross-section geometry and tolerance requirements, but the tool designer also wants to minimize the number of forming steps in order to reduce the investment costs for the customer. There are several computer aided engineering systems on the market that can assist the tool designing process. These include more or less simple formulas to predict deformation during forming as well as the number of forming steps. In recent years it has also become possible to use finite element analysis for the design of roll forming processes. The objective of the work presented in this thesis was to answer the following question: How should the roll forming process be designed for complex geometries and/or high strength steels? The work approach included both literature studies as well as experimental and modelling work. The experimental part gave direct insight into the process and was also used to develop and validate models of the process. Starting with simple geometries and standard steels the work progressed to more complex profiles of variable depth and width, made of high strength steels. The results obtained are published in seven papers appended to this thesis. In the first study (see paper 1) a finite element model for investigating the roll forming of a U-profile was built. It was used to investigate the effect on longitudinal peak membrane strain and deformation length when yield strength increases, see paper 2 and 3. The simulations showed that the peak strain decreases whereas the deformation length increases when the yield strength increases. The studies described in paper 4 and 5 measured roll load, roll torque, springback and strain history during the U-profile forming process. The measurement results were used to validate the finite element model in paper 1. The results presented in paper 6 shows that the formability of stainless steel (e.g. AISI 301), that in the cold rolled condition has a large martensite fraction, can be substantially increased by heating the bending zone. The heated area will then become austenitic and ductile before the roll forming. Thanks to the phenomenon of strain induced martensite formation, the steel will regain the martensite content and its strength during the subsequent plastic straining. Finally, a new tooling concept for profiles with variable cross-sections is presented in paper 7. The overall conclusions of the present work are that today, it is possible to successfully develop profiles of complex geometries (3D roll forming) in high strength steels and that finite element simulation can be a useful tool in the design of the roll forming process.

  • 23. Lindgren, Michael
    et al.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Comparison of Roll Forming Using Different Forming Strategies and Bending2014In: IDDRG 2014, conference proceedings: Innovations for the sheet metal industry, June 1-4 2014, Paris, France / [ed] SFAR Hedi, MAILLARD André, 2014Conference paper (Other academic)
  • 24. Lindgren, Michael
    et al.
    Ingmarsson, Lars-Olof
    3D roll-forming of hat-profile with variable depth and width2009In: Rollform09 1st International congress on roll forming, Bilbao, Spain, 2009Conference paper (Other academic)
    Abstract [en]

    The use of roll-formed products in automotive, furniture, buildings etc. increases every year due to the low part-production cost and the complicated cross-sections that can be produced. The limitation with roll-forming until recent years is that one could only produce profiles with a constant cross-section in the longitudinal direction. About eight years ago ORTIC AB [1] developed a machine in which it was possible to produce profiles with a variable width (“3D roll-forming”) for the building industry. Experimental equipment was recently built for research and prototyping of profiles with variable cross-section in both width and depth for the automotive industry. The objective with the current study is to investigate the new tooling concept that makes it possible to roll-form hat-profiles, made of ultra high strength steel, with variable cross-section in depth and width. The result shows that it is possible to produce 3D roll-formed profiles with close tolerances.

  • 25.
    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.

  • 26.
    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.

  • 27.
    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.

  • 28.
    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)
  • 29.
    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.

  • 30.
    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)
  • 31.
    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)
  • 32.
    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)
  • 33.
    Prosek, Tomas
    et al.
    Institut de la Corrosion / French Corrosion Institute.
    Nazarov, Andrej
    Institut de la Corrosion / French Corrosion Institute.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Thierry, Dominique
    Institut de la Corrosion / French Corrosion Institute.
    Serak, Jan
    Dept. of Metals and Corrosion Engineering, Institute of Chemical Technology, Praha, Czech Republic.
    Corrosion properties of model zinc-magnesium alloys2007In: GALVATECH 2007, 2007Conference paper (Other academic)
    Abstract [en]

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

  • 34.
    Safara Nosar, Nima
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology. KTH Royal Institute of Technology.
    Engberg, Göran
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Ågren, John
    KTH Royal Institute of Technology.
    Modeling microstructure evolution in a martensitic stainless steel subjected to hot working using a physically based model2019In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 50, no 3, p. 1480-1488Article in journal (Refereed)
    Abstract [en]

    The microstructure evolution of a martensitic Stainless steel subjected to hot compression is simulated with a physically based model. The model is based on coupled sets of evolution equations for dislocations, vacancies, recrystallization and grain growth. The advantage of this model is that with only a few experiments, the material dependent parameters of the model can be calibrated and used for a new alloy in any deformation condition. The experimental data of this work is obtained from a series of hot compression, and subsequent stress relaxation tests performed in a Gleeble thermo-mechanical simulator. These tests are carried out at various temperatures ranging from 900 to 1200⁰C, strains up to 0.7 and strain rates of 0.01, 1 and 10 s-1. The grain growth, flow stress, and stress relaxations are simulated by finding reasonable values for model parameters. The flow stress data obtained at the strain rate of 10 s-1 were used to calibrate the model parameters and the predictions of the model for the lower strain rates were quite satisfactory. An assumption in the model is that the structure of second phase particles does not change during the short time of deformation. The results show a satisfactory agreement between the experimental data and simulated flow stress, as well as less than 5% difference for grain growth simulations and predicting the dominant softening mechanisms during stress relaxation according to the strain rates and temperatures under deformation.

  • 35.
    Safara Nosar, Nima
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Sandberg, Fredrik
    Sandvik Materials Technology.
    Engberg, Göran
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Characterization of hot deformation behavior in a 13% chromium steel2018In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 941, p. 458-467Article in journal (Refereed)
    Abstract [en]

    The behavior of a 13% chromium steel subjected to hot deformation has been studied by performing hot compression tests in the temperature range of 850 to 1200 ⁰C and strain rates from 0.01 to 10 s-1. The uniaxial isothermal compression tests were performed on a Gleeble thermo-mechanical simulator. The best function that fits the peak stress for the material and its relation to the Zener-Hollomon parameter (Z) is illustrated. The average activation energy of this alloy for the entire test domain was reviled to be about 557 [kJ mol-1] from the calculations and the dynamic recrystallization (DRX) kinetic were studied to find the fraction DRX in the course of deformation.

  • 36.
    Schultheiss, F
    et al.
    Lunds Universitet.
    Fallqvist, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    M’Sauobi, R
    Seco Tools.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Ståhl, J E
    Lunds Universitet.
    Influence of CVD Al2O3 coated tool surface micro topography on the tribological characteristics in metal cutting: part II2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 298, p. 23-31Article in journal (Refereed)
    Abstract [en]

    The tribological conditions at the contact between the cutting tool and the chip are of great importance when analyzing the machining process. By knowing the contact conditions on the rake face of the cutting tool the wear on the clearance and rake face may be predicted in terms of size and type of wear. A certain value of the surface stresses is often thought of as leading to a higher wear rate of the cutting tool and thus a shorter tool life. In this article two different methods for experimentally measuring the contact condition on the clearance and rake face of the cutting tool are presented and illustrated with results obtained while turning AISI 4140. Results are also obtained in terms of how the surface roughness value of the cutting tool influences the contact condition. It was found that the tool surface topography may have a significant impact on the tribological performance during machining.

  • 37.
    Storck, Joakim
    Dalarna University, School of Technology and Business Studies, Material Science.
    Product variety, flexibility and energy use in hot rolling mills2012In: Enabling Manufacturing Competitiveness and Economic Sustainability: Proceedings of the 4th International Conference on Changeable,Agile, Reconfigurable and Virtual production (CARV2011),Montreal, Canada, 2-5 October 2011 / [ed] ElMaraghy, Hoda, Montreal: Springer, 2012, Vol. 2, p. 80-85Conference paper (Refereed)
    Abstract [en]

    Hot rolling consumes one third of the energy in a steel plant. Increasing product variety slows down production flow, causing heat losses and increased reheating energy consumption. A system dynamics model was developed to evaluate how flexibility influences energy use. Results indicate that world best practice requires high flexibility and low to intermediate product variety. Up to 28% less reheating was needed for low product variety, but no improvement was obtained for high product variety; a flexible steelmaking process for efficient production of small batches of steel would be required. The strategic nature of process flexibility investments is discussed.

  • 38.
    Sveen, Susanne
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology. Linköping University, SE-581 83 Linköping, Sweden.
    Andersson, J
    Seco Tools.
    M’Sauobi, R
    Seco Tools.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Scratch adhesion characteristics of PVD TiAlN deposited on high speed steel, cemented carbide and PCBN substrates2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 308, no 1-2, p. 133-141Article in journal (Refereed)
    Abstract [en]

    Modern tool materials, ranging from powder metallurgical high speed steel to super hard materials such as polycrystalline cubic boron nitride and diamond, are used as cutting tools in the metal cutting industry. In order to further improve the cutting performance, these tools are frequently coated by thin, hard PVD coatings such as TiN, TiAlN, AlCrO3, etc. In order to develop and design new PVD coatings it is important to characterize the mechanical properties of the coatings and understand the coating/substrate deformation mechanisms in a tribological contact, e.g. metal cutting. For example, it is important to be aware that the mechanical properties of the substrate (tool material) have a significant impact on the practical coating adhesion and the coating failure mechanisms.

    In the present study scratch testing has been used in order to evaluate to increase the understanding of the mechanical response and potential coating failure modes of cathodic arc evaporated TiAlN deposited on high speed steel, cemented carbide and polycrystalline cubic boron nitride. Post-test characterization of the scratched samples using optical profilometry, scanning electron microscopy and energy dispersive X-ray spectroscopy were performed and the cohesive and adhesive surface failure mechanisms are described and related to the substrate material properties. The results clearly show that, although all substrate materials can be regarded as hard, they result in completely different coating failure mechanisms at the normal load corresponding to substrate exposure. Also, coating failure resulting in substrate exposure does not necessarily correspond to interfacial cracking resulting in adhesive fracture along the coating-substrate interface.

  • 39.
    Tahir, Mohammed
    Dalarna University, School of Technology and Business Studies, Material Science.
    LOWWEAR varmvalsning WP12012In: Strategiskt stålforskningsprogram för Sverige 2007–2012: En sammanfattning av forskningsprogrammet och de ingående projekten, presenterade vid Jernkontorets programkonferens, 4–5 september 2012, Stockholm: Jernkontoret , 2012, p. 18-18Conference paper (Other (popular science, discussion, etc.))
    Abstract [sv]

    En konstruktion av slitage och temperaturprofiler in-line¬mätare designades och ett modifierat valslitage beräkningsmodell presenteras där inflytandet från arbetsvalsmaterial och det valsade materialets egen-skaper utvärderades. HSS, HiCr och IC arbetsvalsar utvärderades. Olika par i färdigverk med olika valsar-rangemang, skillnader i slitage mellan övre och undre valsar och påverkan av smörjning undersöktes.  Genom att anpassa modellen till olika valsningsförhållanden; varmvalsverk, plåtverk och steckelverk, erhölls möjligheten att undersöka modellen i drift.

    En studie av valsmaterial (Vancron 40, Sverker 3 and Vanadis 23) med avseende på valsslitage, ytkvalitet och påkladdning genomfördes. Valsmaterialen utvärderades experimentellt i laboratorium och i pilotvals-verk. Fyra olika industriella smörjmedel utvärderades. Vancron 40 gav lovande materialkvalitet tack vare sina goda egenskaper gällande ytfinhet i kombination med motstånd mot påkladdning och motstånd mot adhesiv nötning.

  • 40. Wikström, Lars
    et al.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Lindgren, Michael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Partial annealing of stainless steel before roll forming2007In: Stål 2007, 2007Conference paper (Other academic)
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