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  • 1.
    Aiso, Toshiharu
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Kubota, Manabu
    Nippon Steel & Sumitomo Metal Corporation.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Effect of combined additions of Si, Mn, Cr and Al to carbon steel on material transfer in a steel/TiN coated tool sliding contact2017In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 388-389, p. 9-17Article in journal (Refereed)
    Abstract [en]

    Material transferred from steel work materials onto the cutting tools largely affects tool life and machining performance. This material transfer is strongly influenced by the steel composition, and different alloying can have very different effects. Crossed cylinders sliding tests can be used to simulate the contact between the chip and the tool in machining. In this work such a test is used to evaluate material transfer and friction characteristics of a TiN coated tool sliding against five model steels. These model steels are especially designed to study the effects from specific combination of alloy elements, i.e. the steels, containing 0.55 mass% C and 1 mass% Si, are alloyed with one or more of 1 mass% Mn, Cr and Al. When using the steels alloyed without Al, Si-rich oxide layers are formed on the coating, resulting in a low friction coefficient. When using the steels alloyed with Al, almost pure Al–O layers are formed, resulting in a higher friction coefficient and rapid coating cracking. Essentially, the most easily oxidized alloy element is most strongly enriched in the oxide and decides the main mechanism of the material transfer and friction behavior.

  • 2.
    Aiso, Toshiharu
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Kubota, Manabu
    Nippon Steel & Sumitomo Metal Corporation.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Effect of Si and Al additions to carbon steel on material transfer and coating damage mechanism in turning with CVD coated tools2016In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 368-369, p. 379-389Article in journal (Refereed)
    Abstract [en]

    Material transfer from the work materials to the tools strongly influences machining performance and tool life. The influence of Si and Al additions to carbon steel on the material transfer and coating wear in turning with CVD coated carbide tools is investigated. Three model steels are specifically designed to separately study the effects of the individual alloying elements: one reference steel with C as the only alloying element (Base steel), and two steels alloyed also with 1 mass% Si or Al. In the region around the depth of cut on the rake face, where the outside edge of the chip passes over the tool surface, the coating is worn mainly by abrasion when cutting the Base steel. When cutting the Si alloyed steel, an almost pure Si–O transfer layer covers the coating surface, which protects it from wear. When cutting the Al alloyed steel, an almost pure Al–O transfer layer forms on the coating. This layer promotes steel transfer and associated adhesive wear of the coating, which rapidly results in coating detachment and eventually causes notch wear. In the crater region, only the Al alloyed steel results in a transfer layer, an AlN layer that reduces the crater wear.

  • 3.
    Aiso, Toshiharu
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Kubota, Manabu
    Nippon Steel & Sumitomo Metal Corporation.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Effect of Si and Cr additions to carbon steel on material transfer in a steel/TiN coated tool sliding contact2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 97, p. 337-348Article in journal (Refereed)
    Abstract [en]

    A crossed cylinders sliding test, simulating the contact between the chip and the tool in machining, is used to evaluate material transfer and friction characteristics of a TiN coating against specifically designed model steels. These include one base reference, only alloyed with C (Base steel) and two alloyed also with 1 mass% Si or Cr. When sliding against the Base steel, an Fe-O layer is formed on the coating. Against the Si and Cr alloyed steels, Fe-Si-O and Fe-Cr-O layers are formed. In these oxides, Si and Cr are enriched, i.e. preferentially transferred from the steels. Compared to the Base steel, the friction coefficient is significantly lower against the Si alloyed steel and higher against the Cr alloyed steel.

  • 4.
    Aiso, Toshiharu
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Kubota, Manabu
    Nippon Steel & Sumitomo Metal Corporation.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Influence of Mn and Al additions to carbon steel on material transfer and coating damage mechanism in a sliding contact between steel and TiN coated HSS tool2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 101, p. 414-424Article in journal (Refereed)
    Abstract [en]

    A crossed cylinders sliding test, simulating the contact between the chip and the cutting tool, is used to evaluate material transfer, friction characteristics and coating damage of a TiN coated high speed steel against specifically designed model steels. These steels include one reference with C as the only alloy element (Base steel), and two alloyed also with 1 mass% Mn or Al. When sliding against the Base steel, an Fe–O layer forms on the coating and protects it from wear. Against the Mn alloyed steel, Fe–Mn–O forms, which has no protective effect. Against the Al alloyed steel, an almost pure Al–O layer forms. This leads to the highest friction, rapidly causing substrate softening and coating fracture.

  • 5.
    Alfredsson, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Nyberg, Harald
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hogmark, Sture
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Tribological conditions of curling - the ultimate friction sport?2011In: 18th International Conference on Wear of Materials, Philadelphia, USA, April 3-7, 2011, 2011Conference paper (Refereed)
    Abstract [en]

    Curling is an Olympic winter sport in which 8 players forming two teams slide stones across a sheet of ice towards a target area. The two teams have eight stones each and take turns to slide the stones over to the target area, some 28 m away from the release line. After being released, the stone is only affected by the sliding friction. However, this friction may be somewhat modified by sweeping the ice just in front of the sliding stone, using special curling brooms. Further, the trajectory of the stone becomes slightly curled. By slowly turning the stone clockwise when it is released, it will turn to the right, and vice versa. The best team in each round of 16 stones score one point for each stone resting closer to the target than the best stone from the opponent team.

    The game makes up a very interesting tribological system, presenting a number of challenging problems. These problems include understanding exactly:

    • what determines the level of friction, and how it is affected by the sweeping,
    • how the roughness of the stone influences the friction, and how the sliding surface should best be prepared to give a stable and repeatable friction,
    • how the intentionally bumpy "pebbled" ice structure influences the friction,
    • the size and distribution of the contact spots between the rough stone and the pebbled ice,
    • the mechanism causing the curl of the stone - "Why does the stone curl?".

    This poster is based on an experimental project, and presents this very intriguing tribological system. It offers some ready explanations and challenges the visiting tribologists to contribute their insights.

  • 6.
    Andersson, Joakim
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics II. Materials Science. Technology, Department of Engineering Sciences, Electronics. Fysik II.
    Forsberg, Markus
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Department of Physics and Materials Science, Physics II. Materials Science. Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Hollman, Patrik
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Department of Physics and Materials Science, Physics II. Materials Science. Technology, Department of Engineering Sciences, Electronics. Materialvetenskap.
    Jacobson, Staffan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Department of Physics and Materials Science, Physics II. Materials Science. Technology, Department of Engineering Sciences, Electronics. Materialvetenskap.
    A geometrically defined all-diamond pad conditioner2005In: World Tribology Congress III, Washington., 2005Conference paper (Refereed)
  • 7.
    Andersson, Joakim
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Physics II. Materials Science.
    Schmitt, Thorsten
    Department of Physics. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Physics II. Materials Science.
    Duda, Laurent
    Department of Physics. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Physics II. Materials Science.
    Jacobson, Staffan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Physics II. Materials Science.
    Phase transformations in CVD diamond wear tracks revealed by NEXAFS mapping2004In: Nordtrib 2004, Tromsö, Norway, 2004Conference paper (Refereed)
    Abstract [en]

    The origin of the different Li+ intercalation behavior of raw and jet-milled natural graphite has been investigated. Jet-milled graphite is found to cycle reversibly in equal solvent mixture of propylene carbonate (PC) and etylene carbonate (EC), whereas raw graphite does not. Using both Al Ka and synchrotron radiation (SR) Photoelectron Spectroscopy, new insight is obtained inti the formation of the solid electrolyte interphase (SEI) on the two different graphite materials during electrochemical cycling in 1 M LiPF6 in either PC:EC (1:1) or in PC with 5% vinylene carbonate (VC) as additive. Solvent reduction products are found at the surface of both raw and jat-milled graphite cycled in PC:EC (1:1), but differed in composition. The addition of VC reduces primarily the quantities of salt reaction products (LiF and LixPFy compounds) and produces a mainly organic SEI layer. Electron diffraction from the edges for raw and jet-milled graphite particles shows a physical barrier hindering PC co-intercalation and faciltating the formation of a stable SEI layer.

  • 8. Andersson, S
    et al.
    Larsson, R
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Materialvetenskap.
    Höglund, E
    HiMeC - A Swedish Programme for research and Doctoral Studies2006Conference paper (Refereed)
  • 9.
    André, Benny
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Gustavsson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Svahn, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Performance and Tribofilm Formation of a Low-Friction Coating Incorporating Inorganic Fullerene Like Nano-Particles2009Conference paper (Refereed)
    Abstract [en]

    A new tribological coating with potential as a coating for components for low-friction applications is tested and compared to three, state of the art, commercial low-friction PVD coatings. The new coating is an electrodeposited coating composed by a Ni-P matrix incorporating fullerene like nanoparticles of WS2. The performance of the new coating is compared with three reference coatings in a ball-on-disc setup. The tribological tests involved ball bearing steel balls slid on coated discs, under different conditions of humidity and also with or without oil lubrication. Both mating surfaces were closely investigated in a scanning electron microscope and the low-friction tribofilms formed were further analysed. The correlations found between coefficient of friction, surface roughness of the wear scar, tribofilm formation and contact conditions are discussed. The new coating exhibits a very low coefficient of friction at low humidity, a behaviour closely resembling that of the MoS2-based commercial reference, whereas the carbon based PVD coatings tested exhibit the reversed dependence of humidity. The low-friction behaviour of the new coating is correlated to the formation of a WS2 tribofilm with a superficial alignment of the basal planes parallel to the sliding direction. When lubricated with a base oil, the beneficial tribofilm is not formed and the coefficient of friction is much higher. The results show that even though the coating is an electrodeposited coating it can compete with state of the art commercial PVD coatings.

  • 10.
    André, Benny
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Gustavsson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Svahn, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Performance and Tribofilm Formation of a Low-Friction Coating Incorporating Inorganic Fullerene Like Nano-Particles2012In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 206, no 8-9, p. 2325-2329Article in journal (Refereed)
    Abstract [en]

    A new tribological coating with potential as a coating for components for low-friction applications is tested and compared to three, state of the art, commercial low-friction PVD coatings. The new coating is an electrodeposited coating composed by a Ni-P matrix incorporating fullerene like nanoparticles of WS2. The performance of the new coating is compared with three reference coatings in a ball-on-disc setup. The tribological tests involved ball bearing steel balls slid on coated discs, under different conditions of humidity and also with or without oil lubrication. Both mating surfaces were closely investigated in a scanning electron microscope and the low-friction tribofilms formed were further analysed. The correlations found between coefficient of friction, surface roughness of the wear scar, tribofilm formation and contact conditions are discussed. The new coating exhibits a very low coefficient of friction at low humidity, a behaviour closely resembling that of the MoS2-based commercial reference, whereas the carbon based PVD coatings tested exhibit the reversed dependence of humidity. The low-friction behaviour of the new coating is correlated to the formation of a WS2 tribofilm with a superficial alignment of the basal planes parallel to the sliding direction. When lubricated with a base oil, the beneficial tribofilm is not formed and the coefficient of friction is much higher. The results show that even though the coating is an electrodeposited coating it can compete with state of the art commercial PVD coatings.

  • 11.
    André, Benny
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Gustavsson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Svahn, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Potential of a new low-friction coating based on inorganic fullerens: comparison with state-of-the-art PVD coatings2009Conference paper (Refereed)
  • 12.
    André, Benny
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Comparisons between commercial low-friction coatings and emerging coating concepts in ball-on-disc tests – coefficient of friction, tribofilm formation and surface damage2008Conference paper (Refereed)
  • 13.
    Angserud, Jenny
    et al.
    Sandvik Mining.
    From, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wallin, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Norgren, Susanne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    On a wear test for rock drill inserts2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 301, no 1-2, p. 109-115Article in journal (Refereed)
    Abstract [en]

    In this work wear of cemented carbide rock drill inserts is evaluated by using a rotating rock cylinder as counter surface. The influence on wear rate and degradation mechanisms from varying dry and wet conditions, cemented carbide grade, abrasive particle type and size as well as load is studied. The used abrasive media are alumina and silica.

    Test results show high repeatability and the three tested cemented carbide grades can be differentiated, even though their relative difference in sample hardness is modest. The loads used, 100–200 N, are sufficiently high to cause fracture and wear of the granite rock. The degraded microstructure of inserts tested under wet and dry conditions as well as with added silica particles is similar to field worn inserts. Hence, the same wear mechanisms occur and the test successfully mimics rock drill wear. Typical insert wear includes cracking and fragmentation of WC grains, depletion of Co binder phase and adhered material originating from the rock.

    Tests under dry conditions always cause less measured wear than tests under wet conditions.

    Addition of alumina particles, which are harder than the used cemented carbide samples, causes a significant wear rate increase but does not provide wear similar to rock drilling.

  • 14.
    Angserud, Jenny
    et al.
    Sandvik Mining.
    From, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wallin, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Norgren, Susanne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    On a wear test for rock drill inserts2013Conference paper (Refereed)
    Abstract [en]

    In this work wear of cemented carbide rock drill inserts is evaluated by using a rotating rock cylinder as counter surface. The influence on wear rate and degradation mechanisms from varying dry and wet conditions, cemented carbide grade, abrasive particle type and size as well as load is studied. The used abrasive media are alumina and silica.

    Test results show high repeatability and the three tested cemented carbide grades can be differentiated, even though their relative difference in sample hardness is modest. The loads used, 100–200 N, are sufficiently high to cause fracture and wear of the granite rock. The degraded microstructure of inserts tested under wet and dry conditions as well as with added silica particles is similar to field worn inserts. Hence, the same wear mechanisms occur and the test successfully mimics rock drill wear. Typical insert wear includes cracking and fragmentation of WC grains, depletion of Co binder phase and adhered material originating from the rock.

    Tests under dry conditions always cause less measured wear than tests under wet conditions.

    Addition of alumina particles, which are harder than the used cemented carbide samples, causes a significant wear rate increase but does not provide wear similar to rock drilling.

  • 15.
    Beste, Ulrik
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Materials Science.
    Coronel, Ernesto
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Materials Science.
    Jacobson, Staffan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Materials Science.
    Wear induced material modification of cemented carbide rock drills2004In: Conf on Hard Materials, Puert Rico, 2004Conference paper (Refereed)
  • 16.
    Beste, Ulrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Materialvetenskap.
    Coronel, Ernesto
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science. Materialvetenskap.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science. Materialvetenskap.
    Wear induced material modification of cemented carbide rock drills2006In: Int. Journal of Refractory Metals and Hard Materials, Vol. 24, no 1-2, p. 168-176Article in journal (Refereed)
  • 17.
    Beste, Ulrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Coronel, Ernesto
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Wear induced material modifications of cemented carbide rock drill buttons2006In: International journal of refractory metals & hard materials, ISSN 0958-0611, E-ISSN 2213-3917, Vol. 24, no 1-2, p. 168-176Article in journal (Refereed)
    Abstract [en]

    The drill crown of a rock drill is made of steel and equipped with WC/Co cemented carbide buttons (or inserts) of different geometries. These rock drill button are exposed to a large number of high load impacts into the rock. The complex and strongly shifting properties of rock minerals lead to a complex mixture of wear mechanisms. These wear mechanisms have recently been mapped by the present authors, and are divided into five classes of deterioration and five classes of material removal mechanisms. In this paper, two important deterioration mechanisms are studied in detail, namely the binder phase degradation and the rock intermixing.

    Transmission electron microscopy (TEM) has been employed for these high resolution studies. However, rock intermixture and huge internal stresses in the buttons lead to severe difficulties in preparing samples.

    Therefore, a focused ion beam-instrument (FIB) has been used to cut cross-section samples in the outermost surface on rock drill buttons. These have been investigated in the TEM by EDS, EFTEM, and STEM.

    Buttons from two rock drills of different history were selected for this investigation. One was used to drill 18 m in a hard rock type (quartzitic granite) and the other to drill 20 m in a much softer rock type (magnetite). Only selected regions of the outermost WC grain layers, which are in a steady state wear mode, were investigated.

    The crystallographic structure of the Co binder phase was investigated in both buttons, and it was represented mainly by the hcp-Co, but also small extent of fcc-Co. This is suggested to be a result of the mechanical fatigue, following one of two suggested Co-phase transformation series.

    The rock covers and intermixed zones formed were analysed in detail. The large part of the rock cover was found to be amorphous, containing rock and WC fragments. Adjacent to the WC grains, the rock cover was often found to have a porous structure, where the pores were surrounded by crystalline Co-particles adjacent to a carbon rich area. Apparently, the quartz rock locally melts and sticks very intimately to the WC grains and the porous structure forms during solidification. This feature was further analysed, and it was shown that the amorphous rock is seamlessly connected to WC on the atomic level. It was also stated that the rock cover and intermixed layers are very similar on both buttons, independent of rock type drilled.

  • 18. Beste, Ulrik
    et al.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    A new view of the deterioration and wear of WC/Co cemented carbide rock drill buttons2008In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 264, no 11-12, p. 1129-1141Article in journal (Refereed)
    Abstract [en]

    WC/Co cemented carbide is a material developed for highly demanding applications. The unique combination of hardness and toughness makes it especially suitable for wear resistant parts of tools for rock drilling. The wear of cemented carbide rock drill buttons has been the focus of numerous studies, and a large amount of wear data has been published. However, the broad range of possible wear mechanisms, the large number of rock types of very different character, and finally the large local property variations even within a single drill hole, has made it difficult to sort out a good general understanding. One conclusion stands out very clear: the wear data for one rock drill in one rock type is unique to that particular situation and should not be expected to apply to other rock drills in other rock types. Even so, some general wear mechanisms can be observed. Against this backdrop, this paper seeks to present a new, more comprehensive, view on the deterioration and wear mechanisms of cemented carbide rock drill buttons. The new view combines some of most important aspects, including two life limiting factors, five classes of mechanisms of deterioration and five classes of material removal mechanisms. The view is based on careful high resolution investigations of worn rock drill buttons selected from drilling of different rock types. The deterioration includes a fundamental change of material and properties due to intermixing of rock material and cemented carbide in the surface layer of the button. It further includes corrosive decay and oxidation of WC and formation of large-scale cracks in a reptile skin pattern.

  • 19.
    Beste, Ulrik
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Materials Science.
    Jacobson, Staffan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Materials Science.
    Penetrated rock as a weakening mechanism in cemented carbide rock drill wear.2004In: Nordtrib 2004, Tromsö, Norway, 2004, p. 627–636-Conference paper (Refereed)
  • 20. Beste, Ulrik
    et al.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Targeting micro-sectioning: A technique to study subsurface features in worn specimens2008In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 264, no 11-12, p. 1152-1156Article in journal (Refereed)
    Abstract [en]

    Traditional preparation of metallographic cross sections by cutting, polishing and etching has a long and successful history of revealing grain sizes, phase composition, gradients, etc. However, the technique is limited with respect to precision in the positioning of the cross section, and it also tends to inadvertently remove brittle constituents and conceal cracks and small details close to ductile phases, that may become smeared out by the polishing. The present paper presents an alternative cross sectioning technique for worn surfaces, developed to automatically reveal weak zones in the surface layer of a material, without the need of precise positioning, and also avoiding inadvertent removal of brittle phases. The technique is applicable to materials that exhibit brittle fracture, and is normally used for characterisation of unworn materials. It is primarily intended for studies in the SEM, since the cross sections produced typically exhibit too coarse topography to be sharply pictured in the light optical microscope. The simple and rapid preparation technique is described and examples from worn cemented carbide rock drills and hot rolls are presented to illustrate some of the capabilities of the technique.

  • 21. Beste, Ulrik
    et al.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hogmark, Sture
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Rock penetration into cemented carbide drill buttons during rock drilling2008In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 264, no 11-12, p. 1142-1151Article in journal (Refereed)
    Abstract [en]

    In percussive and rotary percussive rock drilling, the rock is crushed into small fragments by the repeated hard impact of the drill bit, and subsequently removed by flushing water or air. To avoid excessive wear, the steel drill bit is equipped with a set of cemented carbide buttons that protrude from the bit to take the actual impact. The severe contact against the rock results in some wear of the button, but also in formation of surface layers of rock material and penetration and impregnation of rock material into the cemented carbide structure. This situation, with serious implications for the wear and fracture of the buttons, have previously not been reported. The present findings represent a significantly new understanding of the wear of the rock button material. The deterioration mechanisms are described in detail, using examples from a range of real drilling applications in different rock types. During operation, material in the surface layer of the drill button shifts from that of the original cemented carbide into an uncontrolled composite. This composite is formed by the WC carbide hard phase and a binder consisting of a mixture of cobalt and rock. This new material should be expected to exhibit properties significantly different from the original cemented carbide.

  • 22.
    Beste, Ulrik
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Materials Science.
    Lundvall, A
    Jacobson, Staffan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Materials Science.
    Micro-scratch evaluation of rock types - a means to comprehend rock drill wear2004In: Trib. Int, Vol. 37, p. 203-210Article in journal (Refereed)
  • 23.
    Duda, Laurent
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Soft X-Ray Physics.
    Andersson, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Schmitt, Thorsten
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Chemical modification in wear tracks of chemical vapor deposited diamond surfaces studied with X-ray absorption spectroscopy2008In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 32, no 1, p. 31-34Article in journal (Refereed)
    Abstract [en]

    We present high-quality X-ray absorption near edge structure spectra of chemical vapor-deposited diamond at the C K-edge recorded with high spatial resolution. We compare unworn surfaces with surfaces worn in Ar-atmosphere, in air, and in water, respectively. Strikingly, the degree of chemical modification in the wear tracks is strongest for wear in an inert Ar-atmosphere which we attribute to the massive creation of unsaturated bonds in the surface vicinity due to high friction forces. We discuss the nature of chemical modification, in particular, whether and to what degree graphitization, amorphization, and ex situ reactions take place.

  • 24.
    Elo, Robin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Heinrichs, Jannica
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Surface texturing to promote formation of protective tribofilms on combustion engine valves2018In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 232, no 1, p. 54-61Article in journal (Refereed)
    Abstract [en]

    In a combustion engine, the valve system controls the flow of gases in to and out of the combustion chamber.The contacting surfaces experience a harsh tribological situation with high temperatures, high speed impacts, corrosiveenvironment and high closing forces causing micro sliding in the interface. The components have to endure in the rangeof hundreds of millions to a billion operational cycles, resulting in extreme demands on low wear rate. Such low wearrates can be accomplished by the protective action from tribofilms forming from oil residues, avoiding a pure metal-tometalcontact. Such tribofilms are found on well-functioning engine valves from a variety of engines, but some stationarygas engines experience problems with wear occurring seemingly randomly at normal running conditions. For somereason, the tribofilm has not protected the surfaces sufficiently, causing wear. One way to combat the random behaviourcould be to promote robust function of the protective tribofilms by texturing the valve sealing surfaces to improve thecapture and storage of oil residues. By stabilising the supply in this way, the damage from periods with low access totribofilm forming material could be reduced. The present work demonstrates that turning of the valve seat inserts,creating valleys perpendicular to the sliding motion, can be developed into a useful solution. The amount and localisationof tribofilms became more predictable and stable than without the texture, leading to reduced component wear. Thevalleys should not be too wide, since this increased the amount of exposed metal if the tribofilm flaked off. When havingthe same width, the deeper valleys showed less flaking off of the tribofilm.

  • 25.
    Elo, Robin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Heinrichs, Jannica
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wear protective capacity of tribofilms formed on combustion engine valves with different surface textures2017In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 376-377, p. 1429-1436Article in journal (Refereed)
    Abstract [en]

    The valve system controls the flow of gases into and out of the cylinders of combustion engines. As the combustion chamber is repeatedly filled with air and emptied from combustion residues, the contacting surfaces of the valve and valve seat insert (VSI) are exposed to high temperatures, high speed impacts, corrosive environment and high closing forces. Since the expected wear life of the components is hundreds of millions of operational cycles, the wear rate has to be extremely low. Previous studies have shown that this is accomplished by the continual formation of protective tribofilms on the surfaces, formed from oil additive residues. For some stationary gas engines, seemingly random occurrence of severe wear, i.e. without correlation to special running conditions, calls for an improved understanding of the wear protective abilities of these tribofilms. Further, the potential of making the protection more robust by using simple textures on sealing surfaces is investigated. Real valves and VSI's were therefore run in a dedicated test rig, previously shown capable of forming tribofilms similar to those found in real engine valves. Two surface textures, turned or ground, were tested. After a running in phase where fully covering tribofilms were formed, the tests were continued without adding the oil residues needed for replenishing the tribofilm. The flow of oil residues was either completely stopped or only intermittently open. The resulting wear was monitored during testing and after finishing the tests remaining tribofilms were analysed with SEM and EDS. The severity of the wear was graded and the presence of tribofilm and localization of wear was correlated. The endurance of the tribofilms was surprisingly high for both textures. Typically the tribofilms exhibited better wear resistance than the underlying metals. Once fully formed, the tribofilms can therefore endure for a long time without addition of new tribofilm forming material. Both textures showed the first sign of wear after roughly the same time and then followed the same progression, when the flow of oil residues was cut. With the intermittent oil residue supply, both textures performed even better. Especially the turned texture showed only slow, mild wear.

  • 26.
    Elo, Robin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Formation and breakdown of oil residue tribofilms protecting the valves of diesel engines2015In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 330-331, p. 193-198Article in journal (Refereed)
    Abstract [en]

    The contacting surfaces of modern valve systems experience a complex contact situation with repeated micro sliding at high temperatures and pressures. The wear rate of the surfaces has to be extremely low to fulfill the high demands on engine efficiency during its entire life-time-wear will cause valve recession and thus make the combustion less efficient. In addition to this, legislation requires reduced particulates in the emissions, which leads to aggravating conditions for the valves. Studies of field samples from well-functioning engines have shown that a protective tribofilm is formed on the contacting surfaces of the valve. This tribofilm is primarily built up from combustion residues of the engine oil and fuel, making its composition sensitive to their additives. Since the low wear rate is dependent on the formation of a tribofilm based on oil residues, while future legislation will demand even cleaner emissions, a deepened understanding about the formation and dynamics of these tribofilms is needed. How quickly are they formed, how quickly do they wear, do they require constant supply of "building material", can they efficiently protect the surfaces also when substantially less building material is available? In the present study, the formation and breakdown mechanisms of this type of protective tribofilms have been investigated in a specifically designed valve rig. This rig uses real engine components and allows controlled addition of oil mist (in the present case from a fully formulated engine oil) into a hot air stream, passing the operating valve. Four phases were identified in the tribofilm dynamics. In the first-formation-phase, oil residue particles become trapped on the sealing surfaces of the valve, and then smeared out between the closing surfaces to form a covering tribofilm. In the second-equilibrium-phase, the tribofilm coverage is stable, meaning that the addition of new particles is balanced by wear of the film. Two types of films form, one thick carbon-based film and one thinner additive-based film. If the supply of oil is cut off, the third-breakdown-phase commences. Here the carbon-based film is quickly removed while the additive-based film keeps protecting the valve surface for numerous closing cycles. When also this film become worn through, the final phase-wear of exposed valve material -commences, involving severe wear and oxidization. Interestingly, it was found that the breakdown was slower if the equilibrium phase was longer, indicating that the additive-based tribofilm becomes more durable by being more worked.

  • 27.
    Elo, Robin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Formation and degradation of protective tribofilms on diesel engine valve surfaces2014Conference paper (Other academic)
    Abstract [en]

    In modern heavy duty diesel engines, the valve system plays an important part. The intake valves open to let air flow in to the combustion chamber, the combustion takes place and then the exhaust valves open the let the combustion products flow out of the chamber. This is repeated as the engine drives the vehicle forward and at all other time, the valves must be closed to avoid any leakage of the combustion chamber which would reduce the power output. This process takes place at high temperature, high chamber pressure and high frequency and the wear rate of the valve surfaces must be extremely low to allow them to operate satisfactory during the life-time of the engine.

    In today’s engines, a tribofilm is formed from elements from the engine oil, which lowers the wear rate and thus gives the valves the wanted long life-time. However, little is known about the mechanisms of how this tribofilm is formed and how it behaves to lower the wear rate. When analyzing field samples, it appears as if additive elements from the oil have been trapped between the valve and valve seat insert surfaces and then as the valve closes, is smeared out into a smooth layer protecting the metal surfaces. The question is how fast this process takes place and if the tribofilm can function without continuous addition of new tribofilm forming elements.

    In this work, the build-up phase of these tribofilm has been studied by running real valves and valve seat inserts in an in-house rig which allows the addition of oil into a hot air stream which passes the opening and closing valve. The rig allows stopping a test at any point, taking the valve and valve seat insert out to analyze the surfaces and then re-starting the test. To see the build-up phase of the tribofilm, tests have been run for 10; 100; 1000 and 10000 cycles with the addition of engine oil. Also, test have been continued after 1000 and 10000 cycles, without the addition of engine oil, for 1000 cycles to see if the tribofilm can sustain the wear rate without the addition of new tribofilm forming elements.

    The results will be presented and discussed regarding their effect on future work to develop the valve system as they will see less and less tribofilm forming elements due to harder legislation on exhaust limits—e.g. the euro class which is implemented in Europe—which may reduce the amount of additives that can be put into future engine oils.

  • 28.
    Elo, Robin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wear mechanism differences of intake valves within heavy duty combustion engines2014Conference paper (Other academic)
    Abstract [en]

    Today, there is an increasing demand on higher efficiency and lower emissions for heavy duty combustion engines. This puts a lot of strain on the different components of the engine. This work is focused on the intake valve system: the valve and valve seat insert. They need to have a low wear rate to survive for an increased operating time but the design of them is a compromise between high efficiency and low wear rate. At the same time they see less and less particulates in the fuel and emissions due to harder legislation that differs around the world, which may hinder the formation of protective tribofilms.

    To deal with the challenge this puts on the developers of the valve system, knowledge is needed about how the tribofilms form and protect the sealing surfaces of the valve and valve seat insert. In an earlier study it was shown that the tribofilms and their wear protecting abilities of the intake valve system vary with different operating conditions regarding allowed emissions from the engine. However, observations from the developers tell not only about differences between engines regarding the wear of the valve system but also sometimes visually large differences of valves coming from the same engine.

    In this study, differences within the same engine are analyzed. Valves have been taken from three different engines. The set of valves from each engine differ in visual appearance and wear. The valves have been examined with scanning electron microscopy and energy dispersive x-ray analysis to see the coverage and composition of tribofilms.

    The results will be presented and discussed regarding the differences within an engine and how these differences compare to the ones between different engines.

  • 29.
    Elo, Robin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wear mechanism study of intake valve system in modern heavy duty combustion engines2014Conference paper (Other academic)
    Abstract [en]

    At the present time, there is an increasing demand on higher efficiency, a longer operational life, and lower amounts of emissions for heavy duty combustion engines. This puts a lot of strain on the different components of the engine, not least the valve and valve seat insert, which operate in direct contact with the combustion chamber. A low wear rate is needed to maintain their sealing and performance abilities, but the design is often a compromise in between high efficiency and low wear rate. At the same time, the sealing surfaces see less and less particulates generated in the engine due to harder environmental legislations which may hinder the formation of protective tribofilms. these changes are expected to change the wear rates of the valve sealing interfaces rapidly.

    In this study, intake valves and valve seat inserts from three different engines have been analyzed. The samples come from two field engines and a cell test and differ in effect, operating time, fuel, and environmental legislation class. The valve sealing surfaces have been examined with high resolution electron microscopy and surface analysis in order to analyze and establish the possible wear mechanisms and presence of protective tribofilms. The results will be presented and their implication with regard to future valve systems will be discussed.

  • 30.
    Eskildsen, Svend
    et al.
    MAN Diesel & Turbo.
    Fogh, Jesper
    MAN Diesel & Turbo.
    Andersson, Henrik
    Olander, Petra
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    On the sulphuric acid corrosion in large 2-stroke marine diesel engines2014In: Tribocorrosion 2014,  9-11 April 2014, University of Strathclyde, Glasgow, 2014Conference paper (Refereed)
  • 31.
    Forsberg, Markus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Andersson, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electronics.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science. Materialvetenskap.
    Geometrically Defined All-Diamond Abrasive Surfaces for Pad Conditioning in Chemical Mechanical Polishing2006In: J Electrochem Soc, Vol. 153, no 1, p. G1-G6Article in journal (Refereed)
  • 32.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Debord, Dominique
    Scania CV AB.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Quantification of Combustion Valve Sealing Interface Sliding - A Novel Experimental Technique and Simulations2014In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 69, p. 150-155Article in journal (Refereed)
    Abstract [en]

    The rapid sharpening of the environmental legislation during the last decades has forced engine manufacturers to radical design modifications. It has been shown that the sliding in the sealing interface is one of the major reasons for wear. The sliding wear is expected to have an even more important role in modern engines. This paper presents unique experimental data, acquired using a dedicated technique in a test-rig. The experimental data is complemented by FEM-simulations. The simulations involve validation of the test-rig valve sealing interface sliding behaviour and investigations on how different parameters influence the sliding length. These parameters include combustion pressure, contact angle, contact length, valve head thickness, coefficient of friction, running-in wear, and change of elastic modulus due to temperature variations.

  • 33.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Elo, Robin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    The importance of oil and particle flow for exhaust valve wear - An experimental study2014In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 69, p. 176-183Article in journal (Refereed)
    Abstract [en]

    Oil residue particles have a large impact in protecting the sealing surfaces of heavy duty exhaust valves. To increase the understanding of the mechanism behind this, the wear behavior of exhaust valves subjected to a flow of hot air with controlled amounts of oil particles of three different compositions has been investigated. Air flow without addition of oil was used as a reference. The degree and mechanisms of surface damage proved to be sensitive to the test parameters. Residues from the oils containing additives proved to form protective tribofilms, while the oil without additives promoted agglomeration of wear debris on the sealing surfaces. The dry reference showed severe wear with debris scattered over the surfaces.

  • 34.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Gustavsson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hollman, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Comparison and analysis of protective tribofilms found on heavy duty exhaust valves from field service and made in test rig2013Conference paper (Refereed)
    Abstract [en]

    Increasing demands from environmental legislations are changing the conditions that the valve system is exposed to in heavy duty engines. Increased pressures, higher temperatures and lower amounts of particulates which can build up a protective film are some of the increasing challenges which the system has to endure. Thick protective tribofilms found on heavy duty exhaust valve surfaces have been analysed with SEM, TEM, EFTEM, STEM-EDS, Nano-indenter and XPS in order to get a better understanding for the tribofilms properties. Two analysed samples are presented in this paper, from a field service truck and another from atest rig which uses vaporised engine oil to simulate the particle flow. The tribofilms are built upfrom several layers with varying compositions. Most of the material originates from oil additives, but also metallic oxides and other carbon compounds produced in the combustion system. The similarities between the rig generated tribofilm and the tribofilm found on the field tested valve verify the test rig behaviour and opens up for realistic wear testing where the importance ofthe protective tribofilm can be investigated in detail that is not possible in motor tests. 

  • 35.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Gustavsson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hollman, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Comparison and analysis of protective tribofilms found on heavy duty exhaust valves from field service and made in test rig2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 302, no 1-2 SI, p. 1351-1359Article in journal (Refereed)
    Abstract [en]

    Increasing demands from environmental legislations are changing the conditions that the valve system is exposed to in heavy duty engines. Increased pressures, higher temperatures and lower amounts of particulates which can build up a protective film are some of the increasing challenges which the system has to endure. Thick protective tribofilms found on heavy duty exhaust valve surfaces have been analysed with SEM, TEM, EFTEM, STEM-EDS, Nano-indenter and XPS in order to get a better understanding for the tribofilms properties. Two analysed samples are presented in this paper, from a field service truck and another from atest rig which uses vaporised engine oil to simulate the particle flow. The tribofilms are built upfrom several layers with varying compositions. Most of the material originates from oil additives, but also metallic oxides and other carbon compounds produced in the combustion system. The similarities between the rig generated tribofilm and the tribofilm found on the field tested valve verify the test rig behaviour and opens up for realistic wear testing where the importance ofthe protective tribofilm can be investigated in detail that is not possible in motor tests. 

  • 36.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Gustavsson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Tribological behaviour for low-friction coatings at conformal contact pressure in traditional and new-alternative fuels2010In: ASIATRIB 2010,  PERTH, WESTERN AUSTRALIA, 5-9 DECEMBER 2010: Frontiers in tribology - knowledge & friendship, 2010Conference paper (Refereed)
  • 37.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Gustavsson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Renman, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hieke, André
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Performance of DLC coatings in heated commercial engine oil2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 304, no 1-2, p. 211-222Article in journal (Refereed)
    Abstract [en]

    Multilayer Diamond Like Coatings (DLC) are widely used to protect highly loaded components from wear and/or to reduce the friction losses in combustion engines. The uppermost layer of the coating controls the chemical situation in the contact and is therefore a very important part of modern multilayer coatings. To examine the individual performances and assess differences and potentials of modern DLC coatings, four commercially available DLCs designed for automotive components with different doping elements together with an uncoated reference were tested in high performance engine oils heated to 90 °C at two different initial contact pressures. The coefficient of friction generally was higher in the tests with the lower initial contact pressure (approximately 20% for all combinations) and the specific wear rate was also up to 100% higher for some combinations. It was also found that a used motor oil showed up to 30% higher friction than when fresh and at the same time reduced the wear in most cases. The tungsten doped coating showed the highest wear, but also the lowest coefficient of friction. The Si doped coating showed the best wear results, most probably due to the ability to make use of the additives in the oil to form a protecting tribofilm.

  • 38.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hollman, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Heavy duty exhaust valve simulation and evaluation in a test rig2012In: Nordtrib, Trondheim, 2012, 2012Conference paper (Refereed)
  • 39.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hollman, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Protective tribofilm build up from exhaust residues on the surface on  exhaust valve systems in a test rig2012In: Nordtrib, Trondheim, Norway, 2012, 2012Conference paper (Refereed)
  • 40.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hollman, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wear mechanism study of exhaust valve system in modern heavy duty combustion engines2011In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 271, no 9-10, p. 2477-2484Article in journal (Refereed)
    Abstract [en]

    The increasing demands from environmental legislations are changing the conditions that the valve system is exposed to in heavy duty engines. Increased pressures, higher temperatures and lower amounts of soot which can build up a protective film are some of the increasing challenges which the system has to endure.

    Three pairs of valves and valve seat inserts with the same material and design properties but with different service condition have been analyzed with a variety of analytical instruments to gain information of how the wear occurs.

    The wear mechanisms found were a combination of oxidation, where many different oxides were found, adhesive wear, which was seen both in form of material transfer and flow lines. On top of Sample Mild and Hard there were tribo films of thickness varying from 1 to 5 mu m consisting of Ca, O, P, S and Zn. The film has in all cases protected the underlying surface from wear but in some cases seems to have a corrosive impact instead.

  • 41.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hollman, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wear study of coated heavy duty exhaust valve systems in a experimental test rig2012Conference paper (Refereed)
  • 42.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hollman, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wear study of coated heavy duty exhaust valve systems in a experimental test rig2012In: SAE International technical papersArticle in journal (Refereed)
  • 43.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Nyberg, Harald
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hollman, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hogmark, Sture
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    The Uppsala Load Scanner –Second generation2010In: Nordtrib 2010, Storforsen, Sweden, 2010Conference paper (Other academic)
  • 44.
    Gustavsson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Bugnet, Matthieu
    Polcar, Tomas
    Cavaleiro, Albano
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    A High-Resolution TEM/EELS Study of the Effect of Doping Elements on the Sliding Mechanisms of Sputtered WS2 Coatings2013Conference paper (Refereed)
    Abstract [en]

    It has been shown many times that cosputtering low-friction coatings of molybdenum disulfide (MoS2) and tungsten disulfide (WS2) with other elements can improve the structural, mechanical, and tribological properties. To achieve the lowest friction, MoS2 or WS2 should be doped with element(s) improving the hardness and density of the coatings. On the other hand, such elements, or their compounds, should not be present in the outermost molecular layers at the sliding interface. This article suggests that there are important differences between how MoS2 and WS2 coatings respond to or react with doping elements, despite the almost identical structure and behavior of the undoped materials. Two systems have been investigated by high-resolution transmission electron microscopy (HRTEM) and scanning TEM (STEM) electron energy loss spectroscopy (EELS), W-S-C-Cr and W-S-C-Ti, and showed significant amounts of oxides, which typically formed a layer just underneath the crystalline WS2 top layer. Further, carbon was almost completely absent in the tribofilms, despite the fact that the as-deposited coatings contained as much as 40-50 at% C. An interesting observation here is that WS2 basal planes surround or embed Fe wear particles, suggesting a relatively strong adhesion or a Fe-S chemical bonding between iron/steel and WS2. The result of this is that the wear particles become pacified and remain in the contact as low-friction material.

  • 45.
    Gustavsson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Bugnet, Matthieu
    Polcar, Tomas
    Cavaleiro, Albano
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    A High-Resolution TEM/EELS Study of the Effect of Doping Elements on the Sliding Mechanisms of Sputtered WS2 Coatings2015In: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 58, no 1, p. 113-118Article in journal (Refereed)
    Abstract [en]

    It has been shown many times that cosputtering low-friction coatings of molybdenum disulfide (MoS2) and tungsten disulfide (WS2) with other elements can improve the structural, mechanical, and tribological properties. To achieve the lowest friction, MoS2 or WS2 should be doped with element(s) improving the hardness and density of the coatings. On the other hand, such elements, or their compounds, should not be present in the outermost molecular layers at the sliding interface. This article suggests that there are important differences between how MoS2 and WS2 coatings respond to or react with doping elements, despite the almost identical structure and behavior of the undoped materials. Two systems have been investigated by high-resolution transmission electron microscopy (HRTEM) and scanning TEM (STEM) electron energy loss spectroscopy (EELS), W-S-C-Cr and W-S-C-Ti, and showed significant amounts of oxides, which typically formed a layer just underneath the crystalline WS2 top layer. Further, carbon was almost completely absent in the tribofilms, despite the fact that the as-deposited coatings contained as much as 40-50 at% C. An interesting observation here is that WS2 basal planes surround or embed Fe wear particles, suggesting a relatively strong adhesion or a Fe-S chemical bonding between iron/steel and WS2. The result of this is that the wear particles become pacified and remain in the contact as low-friction material.

  • 46.
    Gustavsson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Forsberg, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Friction and wear behaviour of low-friction coatings in conventional and alternative fuels2012In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 48, p. 22-28Article in journal (Refereed)
    Abstract [en]

    Today low-friction PVD coatings are used regularly in combustion engines to reduce wear and energy loss due to friction. Three coatings based on transition-metal dichalcogenides and three DLC coatings were tested with respect to tribological behaviour in non-conformal sliding contact, in five conventional and alternative fuels and fuel blending components. The friction and wear proved to vary substantially between the different tested systems. The DLC coatings exhibited extremely good wear properties, but also higher friction. Contrastingly the TMD coatings showed promising friction results, but in their present forms they do not offer sufficient wear resistance in the tested severe contact situation.

  • 47.
    Gustavsson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Forsberg, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Investigations of the friction behaviour and surface modifications for low-friction coatings in traditional and new alternative fuels2010In: NordTrib 2010, 2010Conference paper (Refereed)
  • 48.
    Gustavsson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Forsberg, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Renman, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hieke, André
    Ionbond Netherlands.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    How tribological propertiesof DLC coatings vary in different engine oils at elevated temperature2012In: Nordtrib, Trondheim, Norge, 2012Conference paper (Refereed)
    Abstract [en]

    Improving fuel economy and tribological properties in automotive applications is a continuous quest, where only a few percent decrease in friction and emissions can make a huge difference. Energy savings and environmental influence are today very important factors when designing new tribological systems for automotive applications.

    DLC coatings are often seen as a homogenous group of hard amorphous carbon coatings, being chemically inert with great wear resistance in most lubricated environments. However, the hardness can vary within almost an order of magnitude between different DLC variants and combined with large variations in chemical composition, the wear and friction properties may vary significantly, depending on the test conditions.

    In this study, an experimental coating of amorphous carbon deposited with PA-CVD is compared with three commercially available and optimized DLC coatings, frequently used in automotive applications. The coatings have different hardness, chemical composition and structure.

    The coatings are tested in a reciprocal sliding test rig, at contact pressures and temperature representative of real engines. The tests are performed at low speeds and are designed to operate in the boundary friction regime, where the need for coatings is the highest. An uncoated reference material is tested with the same parameters to highlight the benefits of the coatings under the different test conditions. Five oils are tested, including four special oils designed with different amounts of additives and one used dully formulated engine oil taken from a real engine.

    Results show that the DLCs do not behave as a homogenous group, but have different tribological properties depending on the hardness and composition. Interestingly, the ranking of the coatings varies for the different oils. Special attention is put on friction and wear behavior and on how the surfaces have changed during the test. Further, deeper surface analysis of some selected systems is performed using EDS, XPS and TEM.

  • 49.
    Gustavsson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Forsberg, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Renman, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hieke, André
    Ionbond Netherlands.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Smart DLC coating top coating for reduction of counter surface wear in fuel contact2012In: Faraday Discussion 156: Tribology, 2012Conference paper (Refereed)
  • 50.
    Gustavsson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Forsberg, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Renman, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Formation of tribologically beneficial layer on counter surface with smart chemical design of DLC coating in fuel contact2012In: Tribology - Materials, Surfaces & Interfaces, ISSN 1751-5831, E-ISSN 1751-584X, Vol. 6, no 3, p. 102-108Article in journal (Refereed)
12345 1 - 50 of 214
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