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  • 51.
    Olsson, Mikael
    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.
    Yvell, Karin
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Initial degradation of cemented carbides for rock drilling - Model studies of the tribological contact against rock2015In: International journal of refractory metals & hard materials, ISSN 0958-0611, E-ISSN 2213-3917, ISSN 0263-4368, Vol. 52, p. 104-113Article in journal (Refereed)
    Abstract [en]

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

  • 52.
    Olsson, Mikael
    et al.
    Dalarna University.
    Heinrichs, Jannica
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Yvell, Karin
    Dalarna University.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    On the relevance of hardness as a material parameter in the deformation and wear of cemented carbides in rock drilling2014Conference paper (Other academic)
  • 53.
    Olsson, Mikael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Dalarna Univ, Mat Sci, SE-79188 Falun, Sweden.
    Yvell, K.
    Dalarna Univ, Mat Sci, SE-79188 Falun, Sweden..
    Heinrichs, Jannica
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Bengtsson, M.
    LKAB Wassara AB, SE-14122 Huddinge, Sweden..
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Surface degradation mechanisms of cemented carbide drill buttons in iron ore rock drilling2017In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 388-389, p. 81-92Article in journal (Refereed)
    Abstract [en]

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

  • 54.
    Roizard, X.
    et al.
    Inst FEMTO ST, DMA, CNRS, UBFC,ENSMM,UTBM,UMR 6174, F-25000 Besancon, France..
    Heinrichs, Jannica
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Buteri, A.
    APERAM Isbergues, Res Ctr, BP 15, F-62330 Isbergues, France..
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Borgeot, M.
    Inst FEMTO ST, DMA, CNRS, UBFC,ENSMM,UTBM,UMR 6174, F-25000 Besancon, France.;APERAM Isbergues, Res Ctr, BP 15, F-62330 Isbergues, France.;CNRS, UBFC, Inst UTINAM, UMR 6213, F-25009 Besancon, France..
    Carpentiar, L.
    Inst FEMTO ST, DMA, CNRS, UBFC,ENSMM,UTBM,UMR 6174, F-25000 Besancon, France..
    Melot, J. M.
    CNRS, UBFC, Inst UTINAM, UMR 6213, F-25009 Besancon, France..
    Lallemand, F.
    CNRS, UBFC, Inst UTINAM, UMR 6213, F-25009 Besancon, France..
    Friction behavior of ferritic stainless steel in a strongly diluted alcohol solution of alkylphosphonic acid2018In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 118, p. 465-473Article in journal (Refereed)
    Abstract [en]

    The present study investigates the potential for using this more environmentally friendly lubrication at an industrial scale forming of stainless steel. Against this background we analyze the characteristics of the tribofilm formed on a stainless steel surface during sliding experiments performed in solutions containing alkylphosphonic acids, under various contact conditions. Specific tribological tests were designed to analyze the dynamics of the lubricating mechanism. It was found that both the grafting of molecules and the transformation of these into an efficient tribofihn are quick processes, irrespective of substrate roughness or contact pressure, systematically leading to low friction coefficient.

  • 55.
    Roizard, X.
    et al.
    CNRS UFC ENSMM UTBM, UMR 6174, DMA, Inst FEMTO ST, F-25000 Besancon, France..
    Heinrichs, Jannica
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Taouil, A. Et
    Univ Franche Comte, UMR CNRS 6213, Inst UTINAM, F-25009 Besancon, France..
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Olsson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Dalarna Univ, Mat Sci, SE-79188 Falun, Sweden..
    Melot, J. M.
    Univ Franche Comte, UMR CNRS 6213, Inst UTINAM, F-25009 Besancon, France..
    Lallemand, F.
    Univ Franche Comte, UMR CNRS 6213, Inst UTINAM, F-25009 Besancon, France..
    Insights into sliding wear and friction behavior of copper in ethanol containing alkylphosphonic acid molecules2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 96, p. 141-148Article in journal (Refereed)
    Abstract [en]

    In this work, the friction and wear behavior of bare copper was investigated for the first time under lubricated sliding conditions in diluted ethanol solutions of butylhosphonic (C4P), octylphosphonic (C8P), dodecylphosphonic (C12P), and hexadecylphosphonic (C16P) acids. The technique aims towards a more environmentally friendly lubrication to be used in shaping of copper sheets. Bare copper samples were subjected to unidirectional sliding using a tribometer with ball-on-disk contact geometry. Copper substrates (20 mm(2) x 1 mm) were run against 100Cr6 empty set10 mm ball bearing counterbodies. All tests were conducted using the same sliding conditions with a normal load of 10 N, tangential velocity of 0.01 m/s, at room temperature of 20 degrees C. Worn surfaces were analyzed by Scanning Electron Microscopy, Optical Microscopy and White Light Interference Profilometry. When comparing to sliding tests in the pure ethanol solvent, significant decreases in terms of wear track dimensions, transferred material on the ball and friction coefficients are observed when active molecules are present in the solution. These form protective tribofilms exhibiting lubricating and anti-wear properties. Deeper studies on the tribological behavior of copper in C4P solution show that both low friction and low transfer of work material to the ball prevail in a specific range of low molecule concentration (5 x 10(-4) M; 25 x 10(-4) M). Even if the molecules are introduced during the test, after a few cycles, the tribological behavior improves, regardless of both friction level and copper surface degradation. Finally, specific friction tests were performed to further investigate the mechanisms. It was found that two mechanisms are involved; firstly molecules grafting onto the surface directly reduces friction, and secondly transformation of these grafted molecules into a tribofilm during the first mechanical contact cycles reduces it even further.

  • 56.
    Westlund, Viktoria
    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.
    INVESTIGATION OF MATERIAL TRANSFER IN SLIDING FRICTION-TOPOGRAPHY OR SURFACE CHEMISTRY?2015Conference paper (Other academic)
  • 57.
    Westlund, Viktoria
    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.
    On the Role of Material Transfer in Friction Between Metals: Initial Phenomena and Effects of Roughness and Boundary Lubrication in Sliding Between Aluminium and Tool Steels2018In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 66, no 3, article id 97Article in journal (Refereed)
    Abstract [en]

    In the absence of a lubricant, the friction we measure in sliding contact between metals is typically high and quite erratic, with rapid fluctuations. If we filter out these rapid fluctuations, we can typically also notice slower trends, which can lead to quite dramatic friction changes. Unless careful studies are performed, the cause to this behaviour cannot be understood. How come a material couple cannot be characterised with a specific coefficient of friction? The present paper sets out to add understanding to this area, by conduction and analysing an experimental series involving sliding between a needle-like aluminium tip against tool steel flats. The load is high enough to cause substantial plastic deformation of the aluminium needle; its tip becomes formed by the contact against the tool steel. These small-scale, low sliding distance tests facilitate detailed studies of the initial stages of various friction trends, and the effects of initial surface roughness and shifts of this roughness caused by material transfer between the sliding surfaces. Specifically, the effects on the transfer and friction behaviour from presence or absence of a boundary lubricant film and atmospheric oxygen were studied. It was found that very smooth sliding surfaces can offer low-friction conditions for these metal types. However, the smooth sliding interface is very fragile. In all unlubricated cases tested, it very rapidly (in less than a few mm sliding) became ruined due to transfer, and the friction level correspondingly increased. The boundary lubricant could only offer low friction in cases where the flat steel surface was very smooth. The lubricant also facilitated smoothening of transferred aluminium. As long has been well known, boundary lubrication films typically do not totally hinder direct metallic contact in solid to solid contact. The present results strengthen this view and further suggests that in these direct contacts one of the major friction reducing effects of the lubricant is to efficiently limit transfer, which otherwise acts to make the sliding surface rough.

  • 58.
    Westlund, Viktoria
    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.
    Olsson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Dalarna Univ, Mat Sci, S-79188 Falun, Sweden..
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Investigation of material transfer in sliding friction-topography or surface chemistry?2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 100, p. 213-223Article in journal (Refereed)
    Abstract [en]

    To differentiate between the roles of surface topography and chemical composition on influencing friction and transfer in sliding contact, a series of tests were performed in situ in an SEM. The initial sliding during metal forming was investigated, using an aluminum tip representing the work material, put into sliding contact with a polished flat tool material. Both DLC-coated and uncoated tool steel was used. By varying the final polishing step of the tool material, different surface topographies were obtained. The study demonstrates the strong influence from nano topography of an unpolished DLC coated surface on both coefficient of friction and material transfer. The influence of tool surface chemistry is also discussed.

12 51 - 58 of 58
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