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  • 1.
    Bergström, Jens
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Fatigue and Surface Defects in Tools for Cold Forming1997In: / [ed] J Bergström, T Ericsson, 1997Conference paper (Refereed)
  • 2.
    Bergström, Jens
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Fatigue of Cold Work Steels1998Other (Other (popular science, discussion, etc.))
  • 3.
    Bergström, Jens
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Fatigue of cold work tool steel1999In: Matériaux & Techniques, ISSN 0032-6895, Vol. 87, no 1-2, p. 9-14Article in journal (Refereed)
    Abstract [en]

    One important surface property of forming tools is their resistance to cracking due to fatigue loading. The wide variety of steel grades, material handling, machining operations and surface treatments will give very different fatigue properties. The present article gives examples on the influence of steel grades, EDM machining and surface coating. Initial cracks may be introduced in the tool during the processing to its final shape and surface finish, why a particular interest is given to small cracks introduced by the EDM process.

  • 4.
    Bergström, Jens
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Johansson, M
    Kotik, Ouliana
    Thuvander, Fredrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    The Use of Tool Steels: Experience and Research2002Book (Refereed)
  • 5.
    Bergström, Jens
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Persson, A
    Fatigue of tool steel in cold and hot work applications2000Other (Other (popular science, discussion, etc.))
  • 6.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Electrical Discharge and How it Affects Tool Steels1994Report (Other academic)
  • 7.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Electrical Discharge Machining and its influence on Forming Tools1997Conference paper (Refereed)
  • 8.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Electrical Discharge Machining and the properties of Tool Steels1996Report (Other academic)
  • 9.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Influence of EDM: Post treatments and coatings on mechanical porperties of cold work steels1999Report (Other academic)
    Abstract [en]

    This report is a presentation of results from the laboratory tests of the project Electrical Discharge Machining of Tools in Cold Work Applications. Two high speed steels, two cold work ingot cast and forged steels, and one powder metallurgical cold work steel at hardness from 51 to 66 HRc were included in the study. In the first part of the report differences between the various tool steels in how they respond to electrical discharge machining (EDM) are discussed. Surface alterations, defect distributions, static and fatigue strength are included as well as wire and die sinking EDM, both rough and fine. In the second part some post EDM treatments are examined. The effect of tempering and shot peening after EDM on mechanical properties of the tool steel is shown and a comparison of mechanical polishing and electrochemical polishing (ECP) is given. Since cold work tool steels are being used at increasing hardness, the third part is a study where the hardness of two tool steels has been varied in order to see how important this is to the effect of EDM on mechanical properties of the steel. In the last part the combination of EDM, mechanical or electrochemical polishing and thin ceramic surface coatings are studied, one CVD and one PVD coating

  • 10.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Inverkan av temperatur, dielektrikum och elektrodmaterial på ytegenskaperna hos gnistarbetat varmarbetsstål1992Report (Refereed)
  • 11.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Materialutveckling beträffande formningsverktyg för prototyp och småserier1992Report (Other academic)
  • 12.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Metoder för ytjämnhetsmätning1988Report (Other academic)
  • 13.
    Fredriksson, Gunnel
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Bergström, Jens
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Hogmark, S.
    Crack Growth in Cold Work Tool Steels - Influence of Surface Condition, Microstructure and Hardness1999Conference paper (Refereed)
  • 14.
    Fredriksson, Gunnel
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Bergström, Jens
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Hogmark, S
    Fatigue resistance and surface properties of EDMed cold work tool steels1996Conference paper (Refereed)
  • 15.
    Fredriksson, Gunnel
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Hogmark, S
    Influence of dielectric and temperature in electrical discharge machining of hot work tool steel1996In: Surface Engineering 11Article in journal (Refereed)
  • 16.
    Kazantseva, Natalia
    et al.
    Institute of Metal Physics, Ural Branch of the Russian Academy of Science, Ekaterinburg.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Fredriksson, Gunnel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Yadroitsev, Igov
    Twins in SLM Ti alloy2017In: Titan, ISSN 2075-2903, no 2, p. 8-15Article in journal (Refereed)
  • 17.
    Kazantseva, N.V.
    et al.
    Institute of Metal Physics, Ekaterinburg, Russia.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Fredriksson, Gunnel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Vinogradova, N.I.
    Institute of Metal Physics, Ekaterinburg, Russia.
    Yadroitsev, Igor
    Central University of Technology, Bloemfontein 9300, South Africa.
    Twins in SLM Ti-4Al-6V Alloys2016Conference paper (Refereed)
  • 18.
    Krakhmalev, Pavel
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Fredriksson, Gunnel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Svensson, Krister
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Yadroitsev, Igor
    Bloemfontein Cent Univ Technol South Africa.
    Yadroitsava, Ina
    Bloemfontein Cent Univ Technol South Africa.
    Thuvander, M.
    Chalmers University.
    Peng, R.
    Linköping University.
    Microstructure, solidification texture, and thermal stability of 316 L stainless steel manufactured by laser powder bed fusion2018In: Metals, ISSN 2075-4701, Vol. 8, no 8, p. 1-18, article id 643Article in journal (Refereed)
    Abstract [en]

    This article overviews the scientific results of the microstructural features observed in 316 L stainless steel manufactured by the laser powder bed fusion (LPBF) method obtained by the authors, and discusses the results with respect to the recently published literature. Microscopic features of the LPBF microstructure, i.e., epitaxial nucleation, cellular structure, microsegregation, porosity, competitive colony growth, and solidification texture, were experimentally studied by scanning and transmission electron microscopy, diffraction methods, and atom probe tomography. The influence of laser power and laser scanning speed on the microstructure was discussed in the perspective of governing the microstructure by controlling the process parameters. It was shown that the three-dimensional (3D) zig-zag solidification texture observed in the LPBF 316 L was related to the laser scanning strategy. The thermal stability of the microstructure was investigated under isothermal annealing conditions. It was shown that the cells formed at solidification started to disappear at about 800 °C, and that this process leads to a substantial decrease in hardness. Colony boundaries, nevertheless, were quite stable, and no significant grain growth was observed after heat treatment at 1050 °C. The observed experimental results are discussed with respect to the fundamental knowledge of the solidification processes, and compared with the existing literature data.

  • 19.
    Krakhmalev, Pavel
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Yadroitsava, I.
    Cent Univ Technol, Dept Mech & Mechatron Engn, Private Bag X20539, ZA-9300 Bloemfontein, South Africa.
    Kazantseva, N.
    Urals Branch Acad Sci, Inst Met Phys, Ekaterinburg 620219, Russia.
    Plessis, A. du
    Univ Stellenbosch, CT Scanner Facil, Private Bag 11, ZA-7602 Stellenbosch, South Africa.
    Yadroitsev, I.
    Cent Univ Technol, Dept Mech & Mechatron Engn, Private Bag X20539, ZA-9300 Bloemfontein, South Africa.
    Deformation Behavior and Microstructure of Ti6Al4V Manufactured by SLM2016In: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 83, p. 778-788Article in journal (Refereed)
  • 20.
    Krakhmalev, Pavel
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Yadroitsava, Inna
    Yadroitsev, Igor
    In situ heat treatment in selective laser melted martensitic AISI420 stainless steels2015In: Materials & Design, ISSN 0264-1275, Vol. 87, p. 380-385Article in journal (Refereed)
  • 21.
    Krakhmalev, Pavel
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Yadroitsava, Inna
    Central University of Technology, Free State, South Africa.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Yadroitsev, Igor
    Central University of Technology, Free State, South Africa.
    Microstructural and thermal stability of selective laser melted 316L stainless steel single tracks2017In: South African Journal of Industrial Engineering, ISSN 1012-277X, E-ISSN 2224-7890, Vol. 28, no 1, p. 12-19Article in journal (Refereed)
    Abstract [en]

    To remove residual stresses, an as-built SLM object is usually posttreated. This treatment can affect the microstructure, changing the final mechanical characteristics. This investigation is focused on the microstructural characterisation of 316L austenitic stainless steel in as-built and annealed conditions. The SLM microstructure was relatively stable up to 900°C, when cell boundaries start to disappear. At higher temperatures, an insignificant grain coarsening was detected. These microstructural changes caused a gradual drop in the hardness. The obtained result is background for the future development of post-treatment regimens to achieve a high level in the final mechanical properties of SLM objects.

  • 22.
    Krakhmalev, Pavel
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Yadroitsava, Inna
    Central University of Technology, South Africa.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Yadroitsev, Igor
    Central University of Technology, South Africa.
    Microstructural and thermal stability of selective laser melted 316L stainless steel single tracks2015In: Additive Manufacturing Transforming ideas into business: RAPDASA Rapid Product Development Association of South Africa, 16th Annual International Conference 4-6 November 2015, Roodevallei, Pretoria, South Africa, Pretoria: University , 2015, p. 91-Conference paper (Refereed)
  • 23.
    Krakhmalev, Pavel
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Yadroitsava, Inna
    Central University of Technology, South Africa.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Yadroitsev, Igor
    Central University of Technology, South Africa.
    Microstructure of SLM manufactured 316L and 420 grades stainless steels2014In: PROCEEDINGS 15th Annual International Conference 6 November – 7 November 2014 Stellenbosch, South Africa / [ed] Dimitrov, Dimitar; Becker, Thorsten, Stellenbosch: Stellenbosch University , 2014Conference paper (Refereed)
  • 24. Vilardell, A. M.
    et al.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Fredriksson, Gunnel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Cabanettes, F.
    University of Lyon.
    Sova, A.
    University of Lyon.
    Valentin, D.
    University of Lyon.
    Bertrand, P.
    University of Lyon.
    Influence of surface topography on fatigue behavior of Ti6Al4V alloy by laser powder bed fusion2018In: Procedia CIRP, Elsevier, 2018, p. 49-52Conference paper (Refereed)
    Abstract [en]

    This article deals with the understanding of the influence of surface topography on fatigue behavior of Ti6Al4V alloy specimens produced by laser powder bed fusion (LPBF). The same laser parameters and scan strategy were used for all specimens, giving a sample density higher than 99.5 %. Two different surface topographies were obtained by using the top and side surfaces of the specimens. The surface topography and morphology were investigated by optical surface profilometry and focus variation microscopy. Four-point bending fatigue test was performed on specimens with top and side surfaces as the highest stressed surface respectively. Machined specimens were used as reference. The features of the fracture surface, such as crack initiation and propagation, were analyzed by focus variation and scanning electron microscopy (SEM). Both, fatigue results and fracture surface investigations, were correlated and discussed in relation to surface topography and microstructure, as well as manufacturing parameters. 

  • 25.
    Vilardell, Anna M.
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Fredriksson, Gunnel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Yadroitsev, I.
    Cent Univ Technol Free State, Dept Mech & Mechatron Engn, South Africa.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Fracture mechanisms in the as-built and stress-relieved laser powder bed fusion Ti6Al4V ELI alloy2019In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 109, p. 608-615Article in journal (Refereed)
    Abstract [en]

    The influence of a stress-relief treatment on impact and fatigue properties of Ti6Al4V ELI samples manufactured by laser powder bed fusion was analyzed. The heat treatment resulted in removal of residual stresses, coarsening of needles and formation of precipitations between needles. In both, impact and fatigue tests, crack development was correlated to microstructural features. Fracture analysis was carried out by means of optical and electron microscopy to reveal the influence of microstructure on crack development. Ductile fracture was the dominating fracture mode at impact testing. Pore formation and coalescence were the main crack formation mechanisms. The microstructural changes led to a decrease in impact toughness after heat treatment. Presumably, this was a result of the precipitations between needles. Fatigue results showed multiple crack nucleation at the surface in both, as-built and stress-relieved material. The crack propagation rate was slightly higher and the crack was less deflected in the stress-relieved material due to the stress relief and coarsening of the microstructure.

  • 26.
    Åsberg, Mikael
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Fredriksson, Gunnel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Hatami, Sepehr
    Sverea IVF, Gotenburg.
    Fredriksson, Wendy
    Bodycote Hot Isostatic Pressing AB.
    Influence of HIP on microstructure, pore elimination and tensile properties of SLM manufactured H13 tool steel2017Conference paper (Other academic)
  • 27.
    Åsberg, Mikael
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Fredriksson, Gunnel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Hatami, Sepehr
    Swerea IVF AB.
    Fredriksson, Wendy
    Bodycote Hot Isostatic Pressing.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Influence of post treatment on microstructure, porosity and mechanical properties of additive manufactured H13 tool steel2019In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 742, p. 584-589Article in journal (Refereed)
    Abstract [en]

    Additive manufacturing (AM) is an attractive manufacturing technology in tooling applications. It provides unique opportunities to manufacture tools with complex shapes, containing inner channels for conformal cooling. In this investigation, H13, a widely used tool steel, was manufactured using a laser powder bed fusion method. Microstructure, tensile mechanical properties, hardness, and porosity of the AM H13 after stress relieve (SR), standard hardening and tempering (SR + HT), and hot isostatic pressing (SR + HIP + HT) were investigated. It was found that the microstructure of directly solidified colonies of prior austenite, which is typical for AM, disappeared after austenitizing at the hardening heat treatment. In specimens SR + HT and SR + HIP + HT, a microstructure similar to the conventional but finer was observed. Electron microscopy showed that SR and SR + HT specimens contained lack of fusion, and spherical gas porosity, which resulted in remarkable scatter in the observed elongation to break values. Application of HIP resulted in the highest strength values, higher than those observed for conventional H13 heat treated in the same way. The conclusion is that HIP promotes reduction of porosity and lack of fusion defects and can be efficiently used to improve the mechanical properties of AM H13 tool steel.

1 - 27 of 27
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