du.sePublications
Change search
Refine search result
12345 1 - 50 of 242
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • chicago-author-date
  • chicago-note-bibliography
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the 'Create feeds' function.
  • 1.
    Adegoke, Olutayo
    Dalarna University, School of Technology and Business Studies, Material Science.
    Homogenization of Precipitation Hardening Nickel Based Superalloys2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

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

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

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

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

  • 2.
    Azizoğlu, Yağız
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Gardsback, M.
    Sjoberg, B.
    Lindgren, L. -E
    Finite element modelling of cold pilgering of tubes2015In: Proceedings of the 8th International Conference on Computational Plasticity - Fundamentals and Applications, COMPLAS 2015, 2015, 716-726 p.Conference paper (Refereed)
    Abstract [en]

    Cold pilgering is a cold forming process used during manufacturing of seamless tubes. The tube with a mandrel inside is fed forward and rotated in stepwise increments, while the roll stand moves back and forth. The total plastic deformation of the tube is such that the cross-sectional area of the tube decreases and the length of the tube increases during the process. However, this is performed in many small incremental steps, where the direction of deformation in a material point changes at each stroke. Most published models of cold pilgering use simplified material models. In reality, the flow stress is dependent on temperature, strain rate, strain history and microstructure. In this work, temperature and strain rate distributions are computed, using a 3D thermo-mechanical FE model, and the influence of temperature and strain rate on the rolling force is investigated. The Johnson-Cook model is employed to describe the flow stress using isotropic hardening. The results show that strain rate and temperature have a significant influence on the roll separation force.

  • 3.
    Azizoğlu, Yağız
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology. Luleå University of Technology.
    Gärdsback, Mattias
    Sjöberg, Bengt
    Lindgren, Lars-Erik
    Finite element modeling of tube deformation during cold pilgering2016In: MATEC Web of Conferences, 2016, Vol. 80, 15004Conference paper (Refereed)
    Abstract [en]

    A three-dimensional finite element model of cold pilgering of stainless steel tubes is developed in this paper. The objective is to use the model to increase the understanding of forces and deformations in the process. The focus is on the influence of vertical displacements of the roll stand and axial displacements of the mandrel and tube. Therefore, the rigid tools and the tube are supported with elastic springs. Additionally, the influences of friction coefficients in the tube/mandrel and tube/roll interfaces are examined. A sensitivity study is performed to investigate the influences of these parameters on the strain path and the roll separation force. The results show the importance of accounting for the displacements of the tube and rigid tools on the roll separation force and the accumulative plastic strain.

  • 4.
    Bengtsson, Sebastian
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Påverkan på mätresultatet av slagprovets läge i slagprovmaskinen2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The project assumes that test whether the height of the smaller pendulum test dimensions (10 mm x 7.5 mm, 10 mm x 5 mm and 10 mm x 2.5 mm) is irrelevant to the outcome and to correct for the internal friction in the pendulum test machine. This is because the firm recently received accreditation for the new testing standard. The different materials tested were both brittle and ductile materials from the company and fought at predetermined temperatures. Under this standard, the smaller specimen the results are affected by the pendulum does not hit them in the center. Therefore made some shims (spacers) to raise up the samples so that the pendulum strikes the sample at the center. A comparison between the shim and without shims are made and how the internal friction off the machine can be checked in the smoothest and most appropriate way. The report shows how the samples are manufactured and prepared before they hit, which machines and the different grades used in this thesis. The results of battles show that there is no significant difference with or without shims for the different materials at those predetermined temperatures. Even a paired t-test is done to know whether there is any significant difference between with and without shims. The results of the paired t-tests revealed that the only one of the tests there was a significant difference between with and without the shims. The values of the internal friction shows that the internal friction does not varies much. How to control the internal friction off the machine in the smoothest and most appropriate way is to acquire a system that allows workers must turn blank firing at the beginning of each shift and then check the results and correct results are automatic. Since the centering pin used by the company today centers along the edge of the sample must test bar to be exactly 55 mm long. To get a better alignment can now acquire a centering pin that centers through the notch instead. This is mostly because the centering should not affect the measured test result. The conclusions that can be drawn from the results is that for certain temperatures it does not matter if the test pieces struck with or without shims even if there was one test that was significantly different. Since it is a tiny difference of tenths of a joule and the company reports only integers the difference does not matter. The internal friction does not vary so much that it affects the result.

  • 5.
    Bengtsson, Sebastian
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Validering av ny laserskärande provberedningsteknik inför materialprovning2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this project is to investigate why the 0,2 % proof strength are stronger for the tensile specimens that are produced from laser cutting compare to these that are produced by manual cutting. This phenomenon is likely depending on the higher temperature that’s formed from the laser cutting. An investigation on the choice of the cutting parameters affects the temperature of the test coupon and also how the cutting order could keep the temperature low was made. The Brinell toughness for the laser cut and manual cut plates shall been compared against each other and if it’s necessary to change the size of the laser cut plates. The focus in this project is on the tensile specimens and the Brinell plates.

    The results shown that it’s a significant difference between the laser cut and manual cut tensile specimens and also that the laser cut tensile specimens has a temperature of 120 °C under the cutting process. The various settings for the cutting parameters does not results in any major difference except that a lower ultimate tensile strength, Rm, is shown at the new settings and that the tensile specimens are more likely to get stuck in the coupon. The results from the Brinell hardness tests show that there are no bigger differences between the laser and manual cut test pieces. It also shows that there are no differences between the various milling machines.

    Hardness profiles were made on already milled tensile specimens because according to earlier studies it’s shown that the HAZ disappear after milling. This result shows that it isn’t any bigger difference between the various manufacturing methods, however it’s difficult to interpret the result because the hardness value is resulting from putting the lines manually for calculating the diagonals from the impact. The result can vary with approximately ±5 kg/mm2 because the lines are added manually.

    Pictures of the microstructure was taken see if there is any changes in the structure from the cutting process and no changes in the structure can be determined from these pictures. A statistical analysis was made on all the tests to get a correctly statistical conclusion and these analyses were made in the program MINITAB. The conclusions that are made from the results are that the increase on the 0,2 % proof strength depends likely on epsilon carbides and can be minimized either through a lower or higher temperature in the tensile specimens at the cutting process or adding more Si to the material. There are no differences between the various milling machines at the milling on the Brinell plates or between the laser cut and manually cut plates. There might be some remaining HAZ after the milling on the tensile specimens, however it’s only on the upper part of the specimen.

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

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

  • 7.
    Berger, Robert
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Stavlid, N.
    Grehk, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    The influence of alkali-degreasing on the chemical composition of hot-dip galvanized steel surfaces2006In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 38, no 7, 1130-1138 p.Article in journal (Refereed)
    Abstract [en]

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

  • 8. Berglund, T.
    et al.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    High velocity compaction of high speed steel powder: possibilities and constraints2007In: Proceedings of the Euro Powder Metallurgy Congress and Exhibition, Euro PM 2007, 2007, Vol. 3, 21-26 p.Conference paper (Refereed)
    Abstract [en]

    It is known that gas atomized powders as well as high alloyed metal powders are difficult to press into green bodies using conventional quasi static pressing techniques. However, the development of the high velocity compaction (HVC) technique has expanded the possibility to compact a larger spectrum of metal powders. Although the HVC technique has many similarities with conventional pressing techniques, the high energy impact makes it an interesting technique not only for the pressing of conventional metal powders to green bodies of high density but also for the pressing of "difficult to press metal powders". Today, high speed steel (HSS) is increasingly being used in different types of components. Consequently, there is an increasing interest in the near net shape manufacturing of HSS components. The aim of the present study is to evaluate the possibility to utilize HVC to press green bodies from different types of HSS powder covering both gas and water atomized HSS powders. The results show that the HSS powders investigated differ with respect to compaction properties, i.e. compressibility and green body quality. While the water atomized powders exhibit very good compaction properties, resulting in green bodies of high density, good surface finish and high strength, the gas atomized powders cannot be pressed in the as-atomized condition using HVC. However, agglomerated as well as milled gas atomized HSS powders show significant improved compaction properties compared to the as-atomized powders, although all showed defects of varying sizes depending on the applied energy during compaction.

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

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

  • 10.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Beläggningar till högtemperaturbränsleceller2011In: Stålforskningsdagarna 2011 / [ed] Joakim Storck, Borlänge: Högskolan Dalarna , 2011, 89-99 p.Conference 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.

  • 11.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Berger, Robert
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Grehk, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Sundell, Per-Erik
    Johansson, Mats
    Bonding of vegetable oils to mercapto silane treated metal surfaces: surface engineering on the nano scale2006In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, no 2, 838-841 p.Article in journal (Refereed)
    Abstract [en]

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

  • 12.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Grehk, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    A corrosion study of hot-dip galvanized steel sheet pre-treated with gamma-mercaptopropyltrimethoxysilane2007In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 201, no 8, 4734-4742 p.Article in journal (Refereed)
    Abstract [en]

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

  • 13.
    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, 880-887 p.Article in journal (Refereed)
  • 14.
    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.

  • 15.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Lundberg, M.
    High temperature oxidation of plastically deformed ferritic interconnect steel2011In: ECS Transactions, ISSN 1938-5862, E-ISSN 1938-6737, Vol. 35, no 1, 2463-2470 p.Article in journal (Refereed)
    Abstract [en]

    In this study, thin sheets of a 22% Cr ferritic steel, Sandvik Sanergy HT has been coated with a thin metallic cobalt film. Samples of the coated steel sheet were exposed to two different forming experiments simulating different aspects of sheet metal forming and post high temperature oxidation. The results show that the metallic cobalt film cracks when the steel sheet is subjected to biaxial straining but that the cracks heal at high temperature. Material subjected to modified scratch testing i.e. simulating the contact between sheet metal and forming tool will oxidize in the same manner as non-scratched material. Also, from high temperature corrosion point of view there is no difference between materials formed under lubricated or dry conditions when oxidized. However, from a tribological point of view a lubricated contact situation is preferred.

  • 16.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Stanciu, V.
    Warnicke, P.
    Östh, M.
    Svedlindh, P.
    ToF-SIMS depth profiling of (Ga,Mn)As capped with amorphous arsenic: effects of annealing time2006In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, no 19, 7252-7254 p.Article in journal (Refereed)
    Abstract [en]

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

  • 17.
    Blomberg, J
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Persson, B
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Blomberg, A
    Effects of semi-isostatic densification of wood on the variation in strength properties with density2005In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 39, no 5, 339-350 p.Article in journal (Refereed)
    Abstract [en]

    The variation in strength properties with density was compared between semi-isostatically densified and non-densified wood. Strength properties were compared with published data from earlier studies using other methods for densification. Small clear specimens of eight species were analysed for compression strength in axial, radial and tangential direction, three-point bending and Brinell hardness. After densification, all tested strength properties increased with density, but especially strength perpendicular to grain became lower than expected from the density of non-densified wood. Strength of densified wood relative to what could be expected for non-densified wood of similar density was denoted as `strength potential index'. For axial compression strength and bending strength, strength potential index of individual wood species varied between 0.7 and 1.0, i.e. densified wood is slightly weaker than what could be expected from its density. Strength potential index was lower for properties much determined by strength perpendicular to grain. In radial direction, densified wood was rubbery with low modulus of elasticity and nearly no proportional limit or modulus of rupture. Generally, wood was apparently weakened in proportion to the degree of compression in respective direction. Strength potential index also increased with increasing original density of the species.

  • 18. Blomberg, Jonas
    et al.
    Persson, Bengt
    Dalarna University, School of Technology and Business Studies, Material Science.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Effects of semi-isostatic densification on anatomy and cell-shape recovery on soaking2006In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 60, no 3, 322-331 p.Article in journal (Refereed)
    Abstract [en]

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

  • 19. Borgström, Henrik
    et al.
    Harlin, Peter
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Paiar, Tomaso
    Wang, Yu
    Nyborg, Lars
    Possibilities and constraints of implementing starch consolidated high speed steel in prototyping2008In: Materials Science & Engineering: A, ISSN 0921-5093, Vol. 475, no 1-2, 34-38 p.Article in journal (Refereed)
    Abstract [en]

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

  • 20.
    Böe, Hampus
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Härdprocessens inverkan på sprickuppkomst och spricktillväxt vid induktionshärdning av Ovako 495B: Seghärdning i induktionsline2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Abstract Induction hardening is a rapid thermal hardening process with high demands on the equipment. Ovako Sweden AB in Hällefors performs induction hardening on steel grade 495B and has major problems with crack initiation and propagation. The purpose of this work is to investigate how induction hardening affects the crack initiation and crack growth in the material and find the factors with major influences. It is very important to meet the customer's demands on hardness profile through the whole cross section. Two different tests have been performed where the goal has been to find an operational process that minimizes crack initiation and crack growth. The results of test one showing that the hardening temperature can be reduced from 915 ˚C down to 870 ˚C. Test two shows that cracks can be minimized if the cooling is done with a polymeric coolant instead of pure water and also achieve a more equal hardness profile. Based on the presented results more tests can be carried out to verify a new way of operational process that leads to a heavily reduced risk for cracks in the material. The two most critical bar diameters have been examined with focus upon the hardening temperature and cooling rate.

  • 21. 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, Vol. 157, no 6, C223-C230 p.Article 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.

  • 22.
    Carlsson, Per
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Klang, Hans
    A study of the initial stages of atmospheric corrosion of formed hot dip zinc coated steel1997In: EUROCORR-97, Trondheim, Norway, 1997Conference paper (Other academic)
    Abstract [en]

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

  • 23. Carlsson, Per
    et al.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    PVD coatings for sheet metal forming: a tribological evaluation2006In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 200, no 14-15, 4654-4663 p.Article in journal (Refereed)
    Abstract [en]

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

  • 24.
    Cederberg, Emil
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Utredning om alternativ kontrollmetod av härdresultat hos martensitiskt rostfritt stål2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Morakniv AB is a company that produces knives and ice drill bits. The quality of the material and heat treatment process is an important factor when the products are used in environments where the demand for performance is important. To further verify the quality, in addition to the ordinary hardness testing, they wanted to investigate an alternative test method.

    The tests included one type of material that would be heat treated in four different ways in order to evaluate the mechanical tests. The hardening process was carried out by two different austenitizing temperatures and by two different cooling rates. The hardening process took place in a belt furnace where the samples were continuously fed, heated and cooled in air. After cooling there was a sub-zero treatment followed by tempering. The results were then evaluated by bending test, hardness test and optical microscopy.

    The result showed that a hardening temperature of

    T+10 °C gave a larger standard deviation and higher ductility than at T-normal with respect to the maximum deflection. A lower cooling rate tended to decrease the maximum deflection and reduce the standard deviation. The hardness values did not vary significantly and the standard deviation were considered as negligible. The microscopy images did not show any specific structure changes when comparing the samples from the different heat treatment settings.

  • 25.
    Dalin Nilsson, Anette
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jämförelse av restaustenit i ett härdat verktygsstål för varmarbetsapplikationer: martensitisk och baintisk mikrostruktur2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis has been conducted at Uddeholms AB in Hagfors. Samples and measurements have been made on a tool steel; Uddeholm Dievar. Dievar is a hot work tool steel which is best suited for large tools.

    Retained austenite is always found in hardened high alloyed steel. It is said to decompose into cementite and ferrite during tempering. The decomposition product affects the impact toughness in a negative way. An impaired impact toughness increases the risk for cracking. Using the correct temperature during austenitizing improves the steel properties.

    The sample that have been used varies in austenitizing and in cooling rate. There is a fast cooling and one slow cooling rate which corresponds to cooling of the core in a large tool. A comparison have been made on the microstructure of the different samples, this has been conducted in a SEM. The mapping of phases has also been made with the use of a SEM (Scanning Electron Microscope) and with an ESBD-detector (Electron Backscatter Diffraction). The values on impact toughness have been relative to the content of retained austenite. This report shows how the austenitizing and cooling rate affect the contents of retained austenite and how the content influences the impact toughness.

    The microstructure of the samples varies depending on austenitizing temperature. Some conclusions that can be made from this thesis are that the content of retained austenite increase with the lowering of the temperature during austenitizing when it comes to bainitic micro structure. In the martensitic sample the retained austenite decreases with the austenitizing temperature. During the assembly of the impact toughness values it showed that the samples with the highest content of retained austenite prior tempering were the ones with the lowest value when the test was conducted.

  • 26. Eklund, Sara
    Icke-metalliska inneslutningars inverkan på tre mekaniska provningsmetoder2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report was made as an investigation of how a representative amount of non- metallicinclusions in the tool steel Uddeholm Dievar, affects the different mechanical testingmethods Charpy-V, un-notched impact testing and tensile testing. The goal of this report isto find out which one of the three test methods that gets least affected by the spread ofnon-metallic inclusions? But also see if the un-notched impact test gives a more evenlyspread result than Charpy-V.

    Three charges were selected for testing of the material's toughness, ductility and tensilestrength. The amount inclusions in the material were measured with the help of theprogram INCA feature. This in order to see if the amount of inclusions could beconsidered to be representative in all of three charges. The result of the Charpy V- test andthe un-notched impact test were evaluated in testXpert II and thereafter compiled inMicrosoft Excel. The result of the tensile testing were plotted in three stress- strain graphwhich then were compared against each other. Images were then taken in the SEM onfracture surfaces from Charpy V-specimens in which the values were considered to bedeviating.

    The material Uddeholm Dievar was too ductile for the equipment that was used for unnotchedimpact test. Therefore could the results of this test not be used. The conclusionsthat could be drawn from this study was that the result from tensile testing is the one thatis least affected by the representative amount of non-metallic inclusions. Un-nochedtesting is believed to have a smaller footprint than the Charpy-V. Even though the tensiletest gave a more accurate result than the Charp-V-methods, companies will still continueto use the last-mentioned. This mainly because Charpy V is more cost-effective methodand test bars for this method are less time consuming to produce.

  • 27.
    Engberg, Göran
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Kero, Ida
    Yvell, Karin
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Modeling microstructure development during hot working of an austenitic stainless steel2013In: Materials Science Forum, ISSN 0255-5476, Vol. 753, 423-426 p.Article in journal (Refereed)
    Abstract [en]

    A number of physically based models are combined in order to predict microstructure development during hot deformation. The models treat average values for the generation and recovery of vacancies and dislocations, recrystallization and grain growth and the dissolution and precipitation of second phase particles. The models are applied to a number of laboratory experiments made on 304 austenitic stainless steel and the model parameters are adjusted from those used for low alloyed steel mainly in order to obtain the right kinetics for the influence of solute drag on climb of dislocations and on grain growth. The thermodynamic data are obtained using Thermo-Calc© to create solubility products for the possible secondary phases. One case of wire rolling has been analyzed mainly concerning the evolution of recrystallization and grain size. The time, temperature and strain history has been derived using process information. The models are shown to give a fair description of the microstructure development during hot working of the studied austenitic stainless steel. © (2013) Trans Tech Publications, Switzerland.

  • 28. 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.

  • 29.
    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, 876-881 p.Article 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.

  • 30.
    Engkvist, Josefin
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Canovic, S.
    Liu, F.
    Gotlind, H.
    Svensson, J. -E
    Johansson, L. -G
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Halvarsson, M.
    Oxidation of FeCrAl foils at 500-900 degrees C in dry O2 and O2 with 40% H2O2009In: Materials at High Temperature, ISSN 0960-3409, Vol. 26, no 2, 199-210 p.Article in journal (Refereed)
    Abstract [en]

    High temperature resistant FeCrAl alloys are frequently used in high temperature applications Such as heating elements and metal based catalytic converter bodies. When exposed to high temperatures an adherent, slowly growing, dense aluminium oxide layer forms on the surface, which protects the underlying alloy from severe degradation. The composition, structure and properties of the formed oxide layer are strongly dependent on the alloy composition, temperature and oxidation environment. In this study, the Sandvik 0C404 FeCrAl alloy, in the form of 50 mu m thick foils, was exposed isothermally in the temperature range 500-900 degrees C for 168 hours in dry O-2 and in O-2 with 40 vol.% H2O. The surface morphology, composition and microstructure of the grown oxide scales were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), grazing incidence X-ray diffraction (GI-XRD), Auger electron spectroscopy (AES), and time of flight secondary ion mass spectrometry (TOF-SIMS). The oxidation process was faster at 900 degrees C than at 500 and 700 degrees C. At 500 degrees C a thin (10-20 nm) mixed oxide of Fe, Cr and Al was formed. Exposure at 700 degrees C resulted ill a similar (40-50 nm) duplex oxide, in both dry O-2 and in O-2 With 40 vol.% H2O. These oxide scales consisted of all inner and an outer relatively pure alumina separated by a Cr-rich band. This type of duplex oxide scale also formed at 900 degrees C with a thin inward growing alpha-Al2O3 at the oxide/metal interface and an outward growing layer outside a Cr-rich band. However, at 900 degrees C the Outward growing layer showed two types of oxide morphologies; a thin smooth base oxide and a much thicker nodular oxide grown on top of substrate ridges. In dry O-2 atmosphere, the main part of this outward growing layer had transformed to alpha-Al2O3. Only in the outer part of the thick oxide nodules, metastable alumina was found. When exposed in the presence of water vapour the main pall of the metastable alumina remained untransformed.

  • 31.
    Engkvist, Josefin
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Canovic, Sead
    Hellström, Kristina
    Järdnäs, Anders
    Svensson, Jan-Erik
    Johansson, Lars-Gunnar
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Halvarsson, Mats
    Alumina scale formation on a powder metallurgical FeCrAl alloy (Kanthal APMT) at 900-1100 °C in dry O2 and in O2 + H2O2010In: Oxidation of Metals, ISSN 0030-770X, E-ISSN 1573-4889, Vol. 73, no 1-2, 233-253 p.Article in journal (Refereed)
    Abstract [en]

    A Rapidly Solidified Powder (RSP) metallurgical FeCrAl alloy, Kanthal APMT, was exposed in dry and humid O2 for 72 h at 900–1,100 °C. The formed oxide scales were characterized using gravimetry in combination with advanced analysis techniques (SEM, EDX, TEM, XRD, AES andSIMS). The oxide scales were at all exposures composed of two-layered α-Al2O3 scales exhibiting a top layer of equiaxed grains and a bottom layer containing elongated grains. A Cr-rich zone, originating in the native oxide present before exposure, separated these two layers. The top α-Al2O3layer is suggested to have formed by transformation of outwardly grown metastable alumina, while the inward-grown bottom α-Al2O3 layer had incorporated small Zr-, Hf- and Ti-rich oxide particles present in the alloy matrix. The scale also contained larger Y-rich oxide particles. Furthermore, in the temperature range studied, the presence of water vapour accelerated alloy oxidation somewhat and affected scale morphology.

  • 32.
    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)
  • 33.
    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, 2845-2850 p.Article 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.

  • 34.
    Eriksson, Alexandra
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Kiselhaltens inverkan på slagsegheten hos Charpy-V och oanvisad slagseghetsprovning: Slagseghetsprovning vid rumstemperatur, godstjocklek 150 mm2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The thesis is based on a survey of two ductile iron with different silicon content. The study will provide a deeper understanding of how the results of the impact test of the two material types differ from each other, and how well the two specimen types may reflect the change in the microstructure that should be the result of varied silicon content.  A cast of stair similar form has been cast for the two ductile irons. With a core drilling were drilled to test pieces from two thicknesses and processed. These samples were half each Charpy-V and un-notched test bars. The specimens were divided into eight test series. The samples were used for impact testing and data was compiled. Structural studies have been done in a scanning electron microscope, SEM and light microscopy, LOM and hardness testing by mikrovikers. The materials differ in that the material with the lower silicon content of more graphite modules, has higher impact strength values and are softer than the material with higher silicon content. This is because the perlite has a stronger influence on the impact strength of EN-GJS-400-18. In addition, EN-GJS-400-18 has larger graphite particles. As both pearlite and graphite is likely to have a slightly uneven distribution in the matrix, this will result in a greater spread on the impact strength test values. As for the lower impact strength of EN-GJS-500-14, it can probably be explained by the higher hardness in the matrix due to the silicon solution hardening effect on the matrix. The higher hardness affects the impact strength negatively.

  • 35. Eriksson, C.
    et al.
    Börner, K.
    Nygren, H.
    Ohlson, K.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Billerdahl, N.
    Johansson, M.
    Studies by imaging ToF-SIMS of bone mineralization on porous titanium implants after 1 week in bone2006In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, no 19, 6757-6760 p.Article in journal (Refereed)
    Abstract [en]

    Anodic oxidation was used to grow porous layers on titanium discs. Six different oxidation procedures were used producing six different surfaces. The implants were inserted in rat bone (tibia) for 7 days. After implant retrieval, mineralization (hydroxyapatite formation) on the implant surfaces was investigated using time-of-flight secondary ion mass spectrometry (TOF-SIMS). Bone tissue around the implants was sectioned and stained. The amount of bone in close apposition to the implant was calculated. The porosity showed great variation between the surfaces. Hydroxyapatite was detected on all surfaces. A slight positive correlation between porosity and mineralization was found, although the most porous surface was not the best mineralized one. Bone had formed around all implants after 7 days. The bone-to-metal contact for the porous implants did not differ significantly from the non-porous control. Porosity is known to influence cellular events. The results indicate that porosity could have an initial, positive influence on bone integration of implants, by stimulating the mineralization process. The methods used were found to be suitable tools for investigation of initial healing around implants in bone.

  • 36.
    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, 4045-4051 p.Article 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.

  • 37.
    Ersbjörs, Andreas
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    HÄRDBARHET HOS BORSTÅL – INVERKAN AVBORFÖRSPRÖDNING2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A hardened and tempered component of boron steel, which revealed

    an intergranular fracture after fatigue testing, have been studied. It was suspected

    that the component was embrittled by boron precipitation in the grain boundaries.

    This hypothesis is the motivation for this work. A reference component which

    exhibits good fatigue properties was used. In order to understand the different

    mechanical properties, both samples was studied in detail.

    A small notched specimen from each component were fractured

    in-situ in an auger

    electron microscope (AES) to study the fracture surfaces with minimum oxygen

    contamination. During the AES-analysis, boron nitride in grain boundaries and

    particles containing Ca and Mn was found in both specimen. The fracture was of

    both brittle and ductile mode for both specimen. P and C were found on every

    intergranular surface studied.

    Fracture surfaces, polished and etched cross sections were studied using scanning

    electron microscope (SEM). Micro hardness measurement reveal that the

    microstructure in the material with low fatigue resistance consists of large fraction

    of a softer phase.

    Since both specimen show a lot of defects, boron embrittlement is not the

    contributing factor for low fatigue resistance. The quality of the product would

    probably increase by reducing the amount of defects. The challenging issue is

    quantification of the amount of the softer phase. It is believed that the softer phase

    can be retained austenite or ferrite. Both can occur as a consequence of faulty heat

    treatment, but with different process parameters. A Jominy test showed equal

    hardenability for both components, this indicates heat treatment differences.

  • 38.
    Fallqvist, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Microstructural, Mechanical and Tribological Characterisation of CVD and PVD Coatings for Metal Cutting Applications2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The present thesis focuses on characterisation of microstructure and the resulting mechanical and tribological properties of CVD and PVD coatings used in metal cutting applications. These thin and hard coatings are designed to improve the tribological performance of cutting tools which in metal cutting operations may result in improved cutting performance, lower energy consumption, lower production costs and lower impact on the environment.  In order to increase the understanding of the tribological behaviour of the coating systems a number of friction and wear tests have been performed and evaluated by post-test microscopy and surface analysis. Much of the work has focused on coating cohesive and adhesive strength, surface fatigue resistance, abrasive wear resistance and friction and wear behaviour under sliding contact and metal cutting conditions.

    The results show that the CVD deposition of accurate crystallographic phases, e.g. α-Al2O3 rather than κ-Al2O3, textures and multilayer structures can increase the wear resistance of Al2O3. However, the characteristics of the interfaces, e.g. topography as well as interfacial porosity, have a strong impact on coating adhesion and consequently on the resulting properties.  Through the deposition of well designed bonding and template layer structures the above problems may be eliminated.

    Also, the presence of macro-particles in PVD coatings may have a significant impact on the interfacial adhesive strength, increasing the tendency to coating spalling and lowering the surface fatigue resistance, as well as increasing the friction in sliding contacts.

    Finally, the CVD-Al2Ocoating topography influences the contact conditions in sliding as well as in metal cutting.

    In summary, the work illuminates the importance of understanding the relationships between deposition process parameters, composition and microstructure, resulting properties and tribological performance of CVD and PVD coatings and how this knowledge can be used to develop the coating materials of tomorrow.

  • 39.
    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.

  • 40.
    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, 1111-1119 p.Article 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.

  • 41.
    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.
    Ruppi, S
    Abrasive wear of textured-controlled CVD a-Al2O3 coatings2007In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 202, no 4-7, 837-843 p.Article in journal (Refereed)
    Abstract [en]

    In the present study the wear resistance of some CVD alpha-Al2O3 coatings with different growth textures, i.e. <0001>, <10<(1)over bar>2> and <10<(1)over bar>4>, and a kappa-Al2O3 coating have been investigated using a micro-abrasion test with diamond particles as the abrasive medium. The results show that the softer kappa-Al2O3 coating shows a higher wear rate as compared with the textured alpha-Al2O3 coatings. Of the latter coatings, the 101¯4 textured a-Al2O3 coating shows the lowest wear rate while the <0001> and <10<(1)over bar>2> textured alpha-Al2O3 coatings show similar wear rate. Two different dominant wear mechanisms, i.e. micro cutting and micro chipping, were observed and the latter mechanism is believed to control the wear rate of the Al2O3 coatings investigated. The results obtained are discussed in relation to the dominant wear mechanisms of the coatings identified using scanning electron microscopy.

  • 42.
    Fallqvist, Mikael
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Ruppi, Sakari
    Abrasive wear of multilayer kappa-Al2O3-Ti(C,N) CVD coatings on cemented carbide2007In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 263, no 1-6, 74-80 p.Article in journal (Refereed)
    Abstract [en]

    In the present study the wear resistance of kappa-Al2O3–Ti(C,N) multilayer CVD coatings with different multilayer structures (8, 15, 32 layers of kappa-Al2O3 separated by thin Ti(C,N) layers) have been investigated using a micro-abrasion and a cutting test. The results show that the wear rate of the kappa-Al2O3 multilayer coatings tend to decrease with decreasing layer thickness in the micro-abrasion test and decrease with increasing layer thickness in the cutting tests. The reason for this is mainly due to the difference in wear behaviour depending on temperature. The results obtained are discussed in relation to the dominant wear mechanisms of the coatings which have been identified using scanning electron microscopy and energy dispersive X-ray spectroscopy. The potential of the micro-abrasion test in the characterisation of thin CVD coatings for cutting tool applications is discussed.

  • 43.
    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, 254-261 p.Article 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.

  • 44.
    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, 87-98 p.Article 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.

  • 45.
    Finnkvist Penttinen, Anna
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Nötningsbeständighet av bestrykningsschaber2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A study of the type of wears Böhler‐Uddeholms coating blades are subjected to when

    they are considered to be consumed to handle usage. Their own devices on the

    company in order to determine the abrasion resistance on the coater blades was

    comparable to the pin‐on‐disc application.

    This is to possibly find a standard way to measure the wear of the different blades

    with the currently available application. If one were to succeed in finding a way this

    will result in that one can give customers with more information on the blades and

    give a better customer service.

    Two end‐used coater blades were used to determine the wear that has occurred.

    For the investigation between Böhler‐Uddeholms device and the pin‐on‐disc

    application three different steel blades were used, named Steel |, steel || and

    steel ||| in this rapport.

    The final wear that occurred on the blades was three body abrasion and corrosive

    wear. It will also, because of the basic coating mass, build an adhesive border along

    the edge of the coating blade.

    The apparatus of the company is in the current situation not quite optimal to mimic

    the actual wear that occurs. The pin‐on‐disc application gives a harder abrasive wear

    that can sees in the wear in the industries at the end use.

  • 46. Fisk, Martin
    et al.
    Hansson, Sofia
    Dalarna University, School of Technology and Business Studies, Material Science.
    FE-Simulation of combined induction heating and extrusion in manufacturing of stainless steel tubes2009In: Computational Plasticity (COMPLAS) X: Fundamentals and Applications: proceedings of the tenth International Conference on Computational Plasticity held in Barcelona, Spain, 2th-4th September 2009 / [ed] E. O˜nate and D.R.J. Owen, Barcelona: International Center for Numerical Methods , 2009Conference paper (Refereed)
    Abstract [en]

    The manufacturing process chain for extrusion of AISI 316L tubes is simulatedusing the finite element method. Models of induction heating and expansion is included and thetemperature field in the billet before extrusion is calculated. It is shown that a correct initialtemperature of the billet is needed in order to predict the extrusion force curve in the initialstage of the process.

  • 47.
    Granbom, Ylva
    Dalarna University, School of Technology and Business Studies, Material Science.
    Structure and mechanical properties of dual phase steels: An experimental and theoretical analysis2010Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The key to the understanding of the mechanical behavior of dual phase (DP) steels is to a large extent to be found in the microstructure. The microstructure is in its turn a result of the chemical composition and the process parameters during its production. In this thesis the connection between microstructure and mechanical properties is studied, with focus on the microstructure development during annealing in a continuous annealing line. In-line trials as well as the lab simulations have been carried out in order to investigate the impact of alloying elements and process parameters on the microstructure. Further, a dislocation model has been developed in order to analyze the work hardening behavior of DP steels during plastic deformation. From the in-line trials it was concluded that there is an inheritance from the hot rolling process both on the microstructure and properties of the cold rolled and annealed product. Despite large cold rolling reductions, recrystallization and phase transformations, the final dual phase steel is still effected by process parameters far back in the production chain, such as the coiling temperature following the hot rolling. Lab simulations showed that the microstructure and consequently the mechanical properties are impacted not only by the chemical composition of the steel but also by a large number of process parameters such as soaking temperature, cooling rate prior to quenching, quench and temper annealing temperature. Studying the behavior of DP steels under deformation it was observed that the plastic deformation proceeds inhomogeneously. This was taken into account when developing a dislocation model accurately describing the work hardening behavior for this type of steel. By fitting the dislocation model to experimental stress-strain data it is possible to obtain information about the material’s behavior, e.g. it was observed that only a fraction of the ferrite phase takes part in the initial plastic deformation, which explains the high initial deformation hardening rate in DP steels. Another finding was that the flow stress ferrite grain size sensitivity in DP steels is much larger than that in ferritic steels. Further, the deformation hardening part of the flow stress experiences a ferrite grain size dependence, which is in glaring contrast to that found for ferritic steels.

  • 48.
    Granbom, Ylva
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Ryde, Lena
    Jeppsson, Johan
    Simulation of the soaking and gas jet cooling in a continuous annealing line using dilatometry2010In: Steel Research International, ISSN 1611-3683, Vol. 81, no 2Article in journal (Refereed)
    Abstract [en]

    The present study concerns the simulation of a continuous annealing line (CAL), using dilatometry. Simulations of CAL have been performed on four commercial steel grades with different chemical compositions in order to investigate how the alloying elements C, Mn, Si and B affect the microstructure and hardness of dual phase (DP) and martensitic steels. Three annealing cycles corresponding to those used in a CAL have been applied. When annealing intercritically, as is the case in DP-steel production, the materials do not reach equilibrium during soaking. Mn and C increase the austenite content and consequently the hardness of the materials. Higher levels of Si (0.4?wt %) are required to retard the formation of new ferrite during cooling in the gas jet section, prior to quenching. B increases hardenability effectively when annealing in the austenite region but is not as efficient during intercritical annealing, which implies that boron restrains ferrite nucleation rather than impeding ferrite growth. Results from DICTRA calculations show that it is possible to simulate the phase transformations during soaking, gasjet cooling and quenching.

  • 49.
    Grehk, Mikael
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Berger, Robert
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Investigation of the drying process of linseed oil using FTIR and ToF-SIMS2008In: Proceedings of the 17th International Vacuum Congress/13th International Conference on Surface Science/Internatinal Conference on Nanoscience and Technology, Stockholm, 2008, Vol. 100Conference paper (Refereed)
    Abstract [en]

    The drying process of linseed oil, oxidized at 80 oC, has been investigated with rheology measurements, Fourier transformation infrared spectroscopy (FTIR), and time of flight secondary ion mass spectrometry (ToF-SIMS). The drying process can be divided into three main steps: initiation, propagation and termination. ToF-SIMS spectra show that the oxidation is initiated at the linolenic (three double bonds) and linoleic fatty acids (two double bonds). ToF-SIMS spectra reveal peaks that can be assigned to ketones, alcohols and hydroperoxides. In this article it is shown that FTIR in combination with ToF-SIMS are well suited tools for investigations of various fatty acid components and reaction products of linseed oil.

  • 50.
    Grehk, Mikael
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Engkvist, Josefin
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Richter, Jan H
    Karlsson, Patrik G
    Sandell, Anders
    Initial stages of metal-organic chemical-vapor deposition of ZrO2 on a FeCrAl alloy2007In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 516, no 6, 875-879 p.Article in journal (Refereed)
    Abstract [en]

    The initial stages of metal-organic chemical-vapor deposition of ZrO2 on a model FeCrAl alloy was investigated using synchrotron radiation photoelectron spectroscopy, X-ray absorption spectroscopy, scanning Auger microprobe, and time of flight secondary mass spectrometry. The coatings were grown in ultra-high vacuum at 400 °C and 800 °C using the single source precursor zirconium tetra-tert-butoxide. At 400 °C the coatings mainly consist of tetragonal ZrO2 and at 800 °C amixed ZrO2/Al2O3 layer is formed. The Almetal diffuses from the FeCrAl bulk to themetal/coating interface at 400 °C and to the surface of the coating at 800 °C. The result indicates that the reactionmechanism of the growth process is different at the two investigated temperatures.

12345 1 - 50 of 242
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • chicago-author-date
  • chicago-note-bibliography
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf