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Sökning: swepub > Högskolan Dalarna > Olsson Mikael

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1.
  • 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. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 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.
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2.
  • Karlsson, Patrik, 1973-, et al. (författare)
  • Galling resistance evaluation of tool steels by two different laboratory test methods for sheet metal forming
  • 2012
  • Ingår i: Lubrication Science. - : John Wiley & Sons. - 0954-0075 .- 1557-6833. ; 24:6, s. 263-272
  • Tidskriftsartikel (refereegranskat)abstract
    • Adhesive accumulation of work material on the tool surface is today a major problem in many sheet metal-forming applications. Different laboratory test methods are used to investigate galling with respect to different tool materials, lubricants and process conditions. In the present study, the galling resistance of a modern nitrogen-alloyed powder metallurgy tool steel and an conventional ingot cast D2 type tool steel was evaluated under lubricated sliding against ferritic stainless steel sheets using a commercial pin-on-disc (POD) and an in-house made slider-on-flat-surface (SOFS) tribotester. The investigated tool steels ranked similarly in terms of galling resistanc in both test methods. However, sliding distances to galling were longer for the SOFS equipment due to continuous sliding on new lubricated sheet surface. Best performance was demonstrated by the powder metallurgy tool steel treated to 65 HRC. Differences in friction behaviour and galling initiation were analysed on the basis of the two different working conditions, i.e. open (SOFS) and closed (POD) tribosystems. Copyright © 2012 John Wiley & Sons, Ltd.
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3.
  • Saketi, Sara, et al. (författare)
  • Wear and wear mechanisms of cemented carbide in the turning of Ti6Al4V
  • 2019
  • Ingår i: Materials. - : MDPI AG. - 1996-1944 .- 1996-1944.
  • Tidskriftsartikel (refereegranskat)abstract
    • Titanium and titanium alloys such as Ti-6Al-4V are generally considered as difficult-to-machine materials. This is mainly due to their high chemical reactivity, poor thermal conductivity and high strength, which is maintained at elevated temperatures. As a result, the cutting tool is exposed to rather extreme contact conditions resulting in plastic deformation and wear. In the present work, the mechanisms behind the crater and flank wear of uncoated cemented carbide inserts in the turning of Ti6Al4V are characterized using high resolution scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and high resolution Auger electron spectroscopy (AES).The results show that for combinations of low cutting speeds and feeds crater and flank wear were found to be controlled by an attrition wear mechanism while for combinations of medium to high cutting speeds and feeds a diffusion wear mechanism was found to control the wear. For the latter combinations, high resolution SEM and AES analysis reveal the formation of an approximately 100 nm thick carbon depleted WC-layer at the cemented carbide/Ti6Al4V interface due to the diffusion of carbon into the adhered build-up layers of work material on the rake and flank surfaces.
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4.
  • Borgström, Henrik, 1975, et al. (författare)
  • Possibilities and constraints of implementing starch consolidated high speed steel in prototyping
  • 2008
  • Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 475:1-2, s. 34-38
  • Tidskriftsartikel (refereegranskat)abstract
    • In the starch consolidation (SC) process, a water-based slurry containing powder, starch, dispersant and thickener is used to fabricate near net-shape green bodies that are de-binded and further consolidated by sintering. In this study, gas atomized M3/2 as well as high and low carbon V-rich M4 type high speed steel powder (<150 mu m) are considered, Both material types undergo high volumetric shrinkage during super-solidus liquid phase sintering enabling them to reach near full density. The analyses and the review cover different process aspects like: recipe optimisation, post-gelatinization drying, de-binding and sintering. A SC recipe consisting of 58 vol.% powder, 3 vol.% starch, 1 vol.% dispersant and a thickener solution resulted in a density of >98% than what is theoretically stated after sintering. It is found that the success of the post-gelatinization drying procedure depends on the smoothness of mould material and controlling powder oxidation. The best combination was freeze drying the slurry in a silicon rubber mould. For V-rich alloys a total or partial control of eutectic carbides in the final microstructure could be realized for vacuum and nitrogen sintering atmospheres, respectively.
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6.
  • Bexell, Ulf, et al. (författare)
  • Bonding of vegetable oils to mercapto silane treated metal surfaces : Surface engineering on the nano scale
  • 2006
  • Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 515:2, s. 838-841
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper the bonding of thin vegetable oil films on mercapto silane treated aluminium surfaces has been studied. The silane molecules are attached to the surface by metal-oxygen-silicon bonds. The coupling between the unsaturated bonds of the vegetable oil and the thiol functionalised surface was obtained through a photoinduced thiol-ene reaction. The surfaces were characterised by X-ray photoelectron spectroscopy (XPS). Vegetable oil contains both saturated and unsaturated carbon chains. For the reactions investigated in this study it is the unsaturated carbon chains that can react by a thiol-ene reaction and the results indicate that it is possible to attach a vegetable oil to a metal surface pre-treated with a thiol functionalised silane.
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7.
  • Carlsson, Per, et al. (författare)
  • PVD coatings for sheet metal forming : a tribological evaluation
  • 2006
  • Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 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.
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8.
  • Eriksson, Jenny, 1985-, et al. (författare)
  • Evaluation of galling resistance for some selected combinations of tool steels / stainless steel sheet materials/ lubricants using pin-on-disc testing
  • 2010
  • Ingår i: NordTrib 2010. - Storforsen.
  • Konferensbidrag (refereegranskat)abstract
    • Stainless steels are well known to be prone to cold welding and material transfer in sliding contacts and therefore difficult to cold form unless certain precautions as discussed in this paper are taken. In the present study different combinations of tool steels/stainless steels/lubricants has been evaluated with respect to their galling resistance using pin-on-disc testing. The results show that a high galling resistance is favored by a high stainless steel sheet hardness and a blasted stainless steel sheet surface topography. The effect of type of lubricant was found to be more complex. For example, the chlorinated lubricants failed to prevent metal-to-metal contact on a brushed sheet surface but succeeded on a blasted sheet surface of the same stainless steel material. This is believed to be due to a protective tribofilm which is able to form on the blasted surface, but not on the brushed surface.
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9.
  • Eriksson, Jenny, 1985-, et al. (författare)
  • Tribological testing of commercial CrN, (Ti,Al)N and CrC/C PVD coatings : Evaluation of galling and wear characteristics against different high strength steels.
  • 2011
  • Ingår i: Surface & Coatings Technology. - Lausanne : Elsevier BV. - 0257-8972 .- 1879-3347. ; 205:16, s. 4045-4051
  • Tidskriftsartikel (refereegranskat)abstract
    • The increasing use of high strength steels in a variety of mechanical engineering applications has illuminatedproblems associated with galling in sheet metal forming operations. Galling is a tribological phenomenonassociated with transfer of material from the steel sheet to the tool surface during forming resulting in seizureof the tool/steel sheet contact and extensive scratching of the steel sheet surface. As a result, a number ofconcepts have been developed in order to reduce the tendency of galling in sheet metal forming, including thedevelopment of new dry lubricants, new forming tool steel grades and improved surface engineeringtreatments such as the deposition of low friction CVD- and PVD-coatings. In the present study the potentialperformance of three commercial PVD coatings, including CrN, (Ti,Al)N and a CrC/C DLC-based coating, in theforming of hot and cold rolled high strength steel as well as electro and hot-dip galvanized high strength steelhas been evaluated using pin-on-disc testing under lubricated contact conditions. Post-test examination ofthe tribosurfaces using FEG-SEM and EDS analyses was performed in order to evaluate the mechanismscontrolling the tendency to material transfer and wear. The results show that in contact with the hot and coldrolled steel the material pick-up tendency of the PVD coatings tend to increase in the order CrC/C–CrN–(Ti,Al)N while in contact with the two galvanized steel sheets, the CrC/C and the (Ti,Al)N coating show a significantlylower material pick-up tendency as compared with the CrN coating. Further, the substrate hardness has astrong influence on the wear of the PVD coatings and consequently on the friction characteristics and gallingtendency of the coating/substrate composite. Low substrate hardness, resulting in a low load bearing capacity,increases the tendency to cracking and subsequently chipping of the brittle coating.
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10.
  • Fallqvist, Mikael, 1982-, et al. (författare)
  • Mechanical and tribological properties of PVD-coated cemented carbide as evaluated by a new multi-pass scratch testing method
  • 2012
  • Ingår i: Advances in Tribology. - : Hindawi Limited. - 1687-5915 .- 1687-5923. ; 2012, s. 305209-
  • Tidskriftsartikel (refereegranskat)abstract
    • A new test method based on multi-pass scratch testing has been developed for evaluating the mechanical and tribological properties of thin, hard coatings. The proposed test method uses a pin-on-disc tribometer and during testing a Rockwell C diamond stylus is used as the “pin” and loaded against the rotating coated sample. The influence of normal load on the number of cycles to coating damage is investigated and the resulting coating damage mechanisms are evaluated by post-test scanning electron microscopy. The present study presents the test method by evaluating the performance of Ti0.86Si0.14N, Ti0.34Al0.66N and (Al0.7Cr0.3)2O3 coatings deposited by cathodic arc evaporation on cemented carbide inserts. The results show that the test method is quick, simple and reproducible and can preferably be used to obtain relevant data concerning the fatigue, wear, chipping and spalling characteristics of different coating-substrate composites. Also, the small size of the test region (the radius of the circular scratch track can be as small as 0.5 mm) makes it possible to perform tests within small restricted areas. Consequently, the test method can be used as a virtually non-destructive test and e.g. be used to evaluate the fatigue and wear resistance as well as the cohesive and adhesive interfacial strength of coated cemented carbide inserts prior to cutting tests.
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