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  • Bexell, Ulf, et al. (författare)
  • Characterisation of a Non-Organofunctional Silane Film Deposited on Al, Zn and Al-43.4Zn-1.6Si Alloy Coated Steel, Part II. Interfacial Characterization by ToF-SIMS and AES
  • 2001
  • Ingår i: Surface and Interface Analysis. - 0142-2421. ; 31:3, s. 223-231
  • Tidskriftsartikel (refereegranskat)abstract
    • Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been used to analyse the interface between a non-organofunctional silane and three different metal substrates (aluminium, zinc and an aluminium-zinc alloy). Ion etching using Ga+ ions was used to expose the interfacial region. Ion fragments from the samples were examined carefully where supposed metal-oxygen-silicon ion fragments should appear in the mass spectra. From high mass resolution spectra it was concluded that there exists an AlOSi+ ion fragment at nominal mass m/z = 71 amu on the aluminium and aluminium-zinc alloy substrates and a ZnOSi+ ion fragment at nominal mass m/z = 108 amu on the zinc and aluminium-zinc alloy substrates. These results are further enhanced by the fact that the characteristic ion pattern of ZnOSi+-type ion fragments, composed of different naturally stable zinc and silicon isotopes, in the mass range m/z = 108-112 amu showed the expected relative peak height relations. The presence of these metal-oxygen-silicon ion fragments is a strong indication that chemical interaction between the silane and the metal substrates exists and that the nature of this interaction is due to the formation of a covalent bond between the silane and the metal substrate. Copyright © 2001 John Wiley & Sons, Ltd.
  • Bexell, Ulf, et al. (författare)
  • Tribological Characterisation of an Organic Coating by the use of ToF-SIMS
  • 2003
  • Ingår i: Applied Surface Science. - 0169-4332. ; 203-204, s. 596-599
  • Tidskriftsartikel (refereegranskat)abstract
    • ToF-SIMS has been used to analyse tribological induced chemical changes of organic coatings deposited on steel strip hot-dip coated with a 55.0% Al–43.4% Zn–1.6% Si alloy (Aluzink). The organic coating was a styrene–acrylic co-polymer containing different forming additives. The forming properties of the organic coatings were evaluated with modified scratch testing. The friction curves show that organic coated hot-dip coated steel displays significantly better tribological properties, i.e. lower coefficient of friction and lower wear, as compared to hot-dip coated steel. Furthermore, the organic coatings showing the highest material transfer tendency also show the highest wear. ToF-SIMS spectra show that a transfer film consisting of species from the organic coating is formed on the ball counter surface. Finally, a combination of SEM and ToF-SIMS analysis shows that mechanical failure of the coating dominates, i.e. no tribochemical changes of the coatings could be detected in the wear track.
  • Carlsson, Per, et al. (författare)
  • Tribological Behaviour of Thin Organic Permanent Coatings Deposited on Hot-dip Coated Steel Sheet - a Laboratory Study
  • 2000
  • Ingår i: Surface and Coatings Technology. - Elsevier. - 0257-8972. ; 132:2-3, s. 169-180
  • Tidskriftsartikel (refereegranskat)abstract
    • The forming and handling of hot-dip coated steel sheets is frequently associated with problems such as galling, scratching and discoloration. Recently, a new generation of thin organic coatings has been introduced on the market in order to improve the performance of hot-dip coated steel sheets and reduce these kinds of problems. In summary, these coatings have the potential to increase the formability of the steel sheet without additional lubrication, the anti-finger print properties and the corrosion protection of the product. Besides, they should also provide a pre-treatment for painting, i.e. they can be classified as permanent coatings. In the present study, the tribological behaviour of three different thin organic permanent coatings deposited on hot-dip coated (pure zinc and 55% Al–Zn) steel sheets is evaluated by three different laboratory tests; modified scratch testing, pin-on-disc testing and bending under tension testing. The results obtained show that all tests yield consistent and valuable information concerning the friction and wear properties of the materials and can, therefore, be used in order to study the tribology in sheet metal forming and the performance of different types of permanent coatings. Of the permanent coatings investigated, a pure organic coating shows the lowest coefficient of friction (µ close to 0.1) and the highest wear resistance, thus offering excellent anti-galling properties. In contrast, a mixed organic/inorganic coating displays a relatively high coefficient of friction (µ close to 0.3) and a significantly lower wear resistance. Surface analyses of the tested surfaces show that the thickness and coverage of the thin organic coating play an important role in controlling friction and wear. Furthermore, a thin organic coating optimized for improved formability and handling should display: a high adhesion to the underlying substrate material, a low coefficient of friction, a high load carrying capacity and a high intrinsic wear resistance.
  • Heinrichs, Jannica, et al. (författare)
  • Transfer of titanium in sliding contacts : New discoveries and insights revealed by in situ studies in the SEM
  • 2014
  • Ingår i: Wear. - 0043-1648. ; 315:1-2, s. 87-94
  • Tidskriftsartikel (refereegranskat)abstract
    • Titanium and its alloys generally display poor tribological properties in sliding contacts due to their high chemical activity and strong adhesion to the counter surface. The strong adhesion causes a high tendency to transfer and ultimately galling or build-up edge formation, resulting in severe surface damage. As a result, forming and machining of titanium and its alloys are generally associated with significant problems such as high friction, rapid tool wear and poor surface finish of the formed/machined surface. In the present study, in situ tests in a scanning electron microscope have been performed to increase the understanding of the mechanisms controlling the initial transfer of titanium (Grade 2) in sliding contact with tool surfaces. Tool materials included cover cold work tool steel, cemented carbide, CVD deposited Al2O3 and PVD deposited DLC. In these tests, a relatively sharp tip, representing the titanium work material, slides against a flat surface, representing the tool. The contact conditions result in plastic deformation of the work material against the tool surface, thereby simulating forming or machining. The limited and well-defined contact, along with the possibility to study the sliding in the SEM, makes it possible to correlate local surface variations to transfer of work material and frictional response. Post-test characterization of the contact surfaces was performed by high-resolution SEM, TEM, EDS and EELS. The initial friction was low and stable against all tested materials, but then gradually escalated against all surfaces except the DLC. The friction escalation was associated to increasing levels of transfer, while the DLC stayed virtually free from transfer. From these very initial sliding tests DLC is a promising tool coating in forming and machining of titanium. 
  • Canovic, Sead, et al. (författare)
  • Microstructural Investigation of the Initial Oxidation of the FeCrAlRE Alloy Kanthal AF in Dry and Wet O-2 at 600 and 800 degrees C
  • 2010
  • Ingår i: Journal of the Electrochemical Society. - 0013-4651. ; 157:6, s. 223-230
  • Tidskriftsartikel (refereegranskat)abstract
    • The FeCrAlRE (where RE is reactive element) alloy Kanthal AF was exposed isothermally at 600 and 800°C for 72 h in dry O2 and in O2 with 10 vol % H2O. The mass gains were 3–5 times higher at the higher temperature. The presence of water vapor increased the oxidation rate at 800°C, while no significant effect was observed at 600°C. A thin two-layered oxide formed at 600°C: an outer (Fe,Cr)2O3 corundum-type oxide, containing some Al, and an inner, probably amorphous, Al-rich oxide. At 800°C a two-layered oxide formed in both environments. The inner layer consisted of inward grown a-Al2O3. In dry O2 the originally formed outward grown g-Al2O3 had transformed to a-Al2O3 after 72 h. Water vapor stabilized the outward grown g-Al2O3 and hence no transformation occurred after 72 h in humid environment. RE-rich oxide particles with varying composition (Y, Zr, and Ti) were distributed in the base oxide at both temperatures and in both environments. The RE-rich particles were separated from the alloy substrate by a layer of Al-rich oxide. At 800°C the Y-rich RE particles were surrounded by thick oxide patches in both dry and humid O2.
  • Carlsson, Per, et al. (författare)
  • Friction and wear mechanisms of thin organic permanent coatings deposited on hot-dip coated steel
  • 2001
  • Ingår i: Wear. - Elsevier. - 0043-1648. ; 247:1, s. 88-99
  • Tidskriftsartikel (refereegranskat)abstract
    • Adhesive wear, generally defined as ‘wear due to localised bonding between contacting solid surfaces leading to material transfer between the two surfaces or loss from either surface’ is a common phenomenon in many sliding contact tribosystems, e.g. sheet metal forming operations. In these operations, galling, i.e. seizure of the sheet surface caused by transfer of sheet material to the tool surface, is frequently a problem since it may results in scratching of the formed sheet surface and eventually cracking and fracture of the product due to high friction forces.In order to reduce the coefficient of friction and the galling tendency in sheet metal forming operations thin organic coatings has been introduced on the market with the intention of improving the performance of hot-dip coated steel sheet. In summary, these coatings have the potential to increase the formability without additional lubrication and serve as temporary corrosion protection during transportation. In the present study, the friction and wear mechanisms of five different thin organic permanent coatings deposited on hot-dip coated (Zn and 55% Al–Zn) steel sheet is evaluated by modified scratch testing.The results obtained show that this test method permits easy and reproducible evaluation of the tribological properties of thin organic coatings. Further, these coatings show a high potential when it comes to improve the formability of hot-dip coated steel. The results obtained are discussed in relation to the identified friction and wear mechanisms.
  • Carlsson, Per, et al. (författare)
  • PVD coatings for sheet metal forming : a tribological evaluation
  • 2006
  • Ingår i: Surface & Coatings Technology. - 0257-8972. ; 200:14-15, s. 4654-4663
  • Tidskriftsartikel (refereegranskat)abstract
    • The use of liquid-based lubricants in sheet metal forming mutually has a negative impact on the environment and on the whole economy, and, consequently, there is an urgent need to find a solution to make the forming processes dry or nearly dry. The deposition of a low-friction PVD coating on the forming tool has during the last years proved to be an interesting choice when it comes to create an “unlubricated” forming process. In the present study, five different PVD coatings (one CrN and four metal-carbide-doped DLC coatings) have been evaluated in sliding contact against hot dip Zn and 55% Al–Zn-coated steel sheet using a ball-on-disc test. From the investigation, it was found that all DLC coatings have potential to prevent material pickup during dry forming of hot dip Zn-coated steel. However, the as-deposited surface morphology, showing surface irregularities such as droplets and dimples, of the coatings will strongly influence the tribological performance, and, consequently, a polishing treatment or a running-in process, resulting in a smooth surface, will significantly reduce the tendency to material pickup. In sliding contact against 55% Al–Zn-coated steel, all PVD coatings display material pickup and high friction values, the only exception being a CrC-doped DLC coating in the as-polished condition. The CrN coating showed poor performance in sliding contact against both steel sheet materials due to a high tendency to material pickup. The study focuses on the tribo-induced changes of the surface condition of the PVD coating and the steel sheet surface during the sliding event. The changes in surface chemistry and topography of the tribo surfaces were characterised using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Auger electron spectroscopy (AES) and light interference profilometry.
  • Carlsson, Per, et al. (författare)
  • Tribological Performance of Thin Organic Permanent Coatings Deposited on 55%Al-Zn Coated Steel – Influence of Coating Composition and Thickness on Friction and Wear
  • 2001
  • Ingår i: Wear. - 0043-16.48. ; 251:1-12, s. 1075-1084
  • Tidskriftsartikel (refereegranskat)abstract
    • Dry lubricants are today increasingly being used in various types of sheet metal forming operations. Among these, permanent coatings, based on organic resins are the only lubricants which have the potential to increase the formability without additional lubrication, serve as temporary corrosion protection during transportation and, finally, serve as a pre-treatment before subsequent painting.In the present study, the influence of coating composition and thickness on the friction and wear behaviour of different thin organic permanent coatings deposited on 55%Al–Zn coated steel sheet have been evaluated by various types of laboratory tests. Surface profilometry, scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and time-of-flight secondary ion mass spectrometry (ToF–SIMS) were used in order to characterise and model the tribological behaviour of the coatings.The results obtained show that the tribological properties of thin organic permanent coatings are strongly influenced by the coating thickness. In order to reduce problems associated with high friction and galling, the coating must be deposited with a uniform thickness, i.e. uncoated regions must be avoided. Furthermore, the addition of various types of additives can be used in order to further improve the tribological performance of these types of coatings.
  • Engkvist, Josefin, et al. (författare)
  • Alumina scale formation on a powder metallurgical FeCrAl alloy (Kanthal APMT) at 900-1100°C in dry O2 and in O2 + H2O
  • 2010
  • Ingår i: Oxidation of Metals. - 0030-770X. ; 73:1
  • Tidskriftsartikel (refereegranskat)abstract
    • A Rapidly Solidified Powder (RSP) metallurgical FeCrAl alloy, Kanthal APMT, was exposed in dry and humid O2 for 72 h at 900–1,100 °C. The formed oxide scales were characterized using gravimetry in combination with advanced analysis techniques (SEM, EDX, TEM, XRD, AES andSIMS). The oxide scales were at all exposures composed of two-layered ?-Al2O3 scales exhibiting a top layer of equiaxed grains and a bottom layer containing elongated grains. A Cr-rich zone, originating in the native oxide present before exposure, separated these two layers. The top ?-Al2O3layer is suggested to have formed by transformation of outwardly grown metastable alumina, while the inward-grown bottom ?-Al2O3 layer had incorporated small Zr-, Hf- and Ti-rich oxide particles present in the alloy matrix. The scale also contained larger Y-rich oxide particles. Furthermore, in the temperature range studied, the presence of water vapour accelerated alloy oxidation somewhat and affected scale morphology.
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