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  • 51.
    Hardell, Jens
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Steinhoff, Kurt
    University of Kassel.
    High temperature tribological studies on surface engineered tool steel and high strength boron steel2009Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 80, nr 9, s. 665-670Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The popularity of hot sheet metal forming processes in the recent years has necessitated research efforts to improve tool life and control the friction level during hot forming operations. In this work, the tribological properties of tool steel and ultra high strength boron steel (UHSS) pairs at elevated temperatures have been studied by using a special hot sheet metal forming test rig that closely simulates the conditions prevalent in the real process. This test involves linear unidirectional sliding of a preheated UHSS sheet between two tool steel specimens where new workpiece material is continuously in contact with the tool surface. The study is aimed at investigating different surface treatments/coatings applied on either the tool or sheet surface or on both. The results have shown that it is possible to control the coefficients of friction through surface treatments and coatings of the tool and workpiece materials. The application of a coating onto the sheet material has a greater influence on the friction compared to changing the tool steel surface. After running-in, the investigated tool steel variants show almost similar frictional behaviour when sliding against the same sheet material. Although coating the UHSS sheet reduces friction, it abrades the tool surface and also results in transfer of the sheet coating material to the tool surface

  • 52. Hardell, Jens
    et al.
    Quang, Hoai Le
    Luleå tekniska universitet.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Tribological performance of surface coated tool steel at elevated temperatures2008Ingår i: Proceedings of NORDTRIB 2008: 13th Nordic Symposium of Tribology / [ed] Jaakko Kleemola; Arto Lehtovaara, Tampere University of Technology, 2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    In metal forming at elevated temperatures the tools are subjected to thermal cycling, increased oxidation and wear which will influence the lifetime of the tools and the quality of the produced parts. In addition to this, the frictional behaviour will also change with temperature and this can affect the performance of the forming operation itself. One way of controlling friction and reducing wear is to utilise the latest developments in surface engineering and modify or coat the tool surface with some thermally stable layer. However, in the open literature there are very few studies pertaining to the high temperature tribological properties of surface coatings applied on to the tool steels and sliding against actual workpiece material. This study thus aims at experimentally investigating the friction and wear characteristics of a surface coated tool steel during sliding against ultra high strength boron steel at elevated temperatures. The surface coatings applied on the tool steel in this work were of TiAlN and CrN respectively. The tribological studies were conducted by using both a reciprocating tribometer as well as a pin-on-disc machine at temperatures in the range from ambient to 800 ºC. A 3D optical surface profiler has been used for surface topography measurements and SEM/EDS have been used for investigating the resultant surface damage. The results have shown that the friction coefficient increases with temperature in unidirectional sliding. Wear of the coatings is negligible at room temperature but at 400 ºC the CrN disc is worn by abrading action of hard oxidised wear debris and the coating is removed to a large extent. In reciprocating sliding the friction also increases with temperature and the coatings are completely removed during sliding at 800 ºC.

  • 53.
    Hardell, Jens
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Yousfi, Amine
    Luleå University of Technology.
    Lund, Martin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Pelcastre, Leonardo
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Abrasive wear behaviour of hardened high strength2014Ingår i: Tribology - Materials, Surfaces & Interfaces, ISSN 1751-5831, E-ISSN 1751-584X, Vol. 8, nr 2, s. 90-97Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Abrasive wear in industrial applications such as mining, materials handling and agricultural machinery constitutes a large part of the total wear. Hardened high strength boron steels are known for their good wear resistance and mechanical properties, but available results in the open literature are scarce. This work aims at investigating how different quenching techniques affect the two-body abrasive wear resistance of hardened high strength boron steels. Furthermore, the wear as a function of depth in thicker hardened high strength boron steel plates has also been studied. The material characterisation has been carried out using microhardness, SEM/energy dispersive spectroscopy and three-dimensional optical surface profilometry. The results have shown that water quenched and tool quenched high strength boron steel had similar wear resistance. The main wear mechanisms appear to be microcutting combined with microfatigue. Workhardening during the abrasion process has been found to affect the abrasive wear.

  • 54.
    Hardell, Jens
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Yousfi, Amine
    Luleå University of Technology.
    Lund, Martin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Pelcastre, Leonardo
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Abrasive wear behaviour of hardened high strength boron steel2013Konferensbidrag (Refereegranskat)
  • 55.
    Hernandez, Sinuhe
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Courbon, Cedric
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Winkelmann, H.
    AC²T research GmbH - Austrian Center of Competence for Tribology, Viktor-Kaplan-Straße 2 D, 2700 Wiener Neustadt.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    High temperature friction and wear mechanism map for tool steel and boron steel tribopair2014Ingår i: Tribology - Materials, Surfaces & Interfaces, ISSN 1751-5831, E-ISSN 1751-584X, Vol. 8, nr 2, s. 74-84Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tribological systems working under severe conditions like high pressures, sliding velocities and temperatures are subjected to different phenomena such as wear, oxidation and changes in mechanical properties. In many cases, there are several mechanisms occurring simultaneously.The predominating type(s) of wear mechanism(s) presented will depend on the materials in contact, operating parameters and surrounding environment. In this work, high temperature tribological studies of boron steel sliding against tool steel were conducted using a pin-on-disc machine under unlubricated conditions at five different temperatures ranging from 25 to 400C, three different loads: 25, 50 and 75 N (contact pressures of 2, 4 and 6 MPa respectively) and a sliding speed of 0.2 ms-1. Scanning electron microscopy/energy dispersive spectroscopy and X-ray techniques were used for analysing the resulting damage and tribolayers of the worn surfaces. Additionally, hardness measurements were carried out in a special hot hardness rig in the same temperature range as that used in pin-on-disc tests. The results have shown that for a given load, the wear rate of boron steel decreased as the temperature increased, reaching itslowest value at 400C at 50 N. In the case of the tool steel, it could be observed that at 200C and above, the wear rate decreased as the load increased. This behaviour is consistent with the formation of a protective oxidised layer initiated at 100C. At higher temperatures, such layers become more pronounced. The obtained data were finally used to construct a friction and wear mechanism map for this material pair that takes temperature and pressure into account.

  • 56.
    Hernandez, Sinuhe
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Courbon, Cedric
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Winkelmann, Horst
    AC²T research GmbH - Austrian Center of Competence for Tribology, Viktor-Kaplan-Straße 2 D, 2700 Wiener Neustadt.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Influence of load on friction and wear of tool steel - boron steel pair at elevated temperatures2013Konferensbidrag (Refereegranskat)
  • 57.
    Hernandez, Sinuhe
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    High temperature wear mechanism map for tool steel and high strength boron steel2012Ingår i: 15th Nordic Symposium on Tribology - NordTrib 2012: 12 - 15 June 2012 - Trondheim, Norway, Trondheim: Department of Geography, Norwegian University of Science and Technology, 2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Machine components moving relative to each other at elevated temperatures can be found in applications such as power generation, aerospace, metal working, etc. The identification and understanding of the wear mechanisms are extremely important for solving problems related to systems operating at high temperatures. Presentation of the results in the form of wear maps enables e.g. design engineers to select appropriate materials for these applications [1, 2].In this study, unidirectional sliding wear tests of ultra-high strength boron steel against tool steel were conducted under unlubricated conditions using a pin-on-disc machine.Studies ranging from room temperature to 300 °C with a sliding speed of 0.2 ms-1 and a contact pressure of 2 MPa were carried out. Wear rates of both materials were obtained by weight loss measurements. Surface damage and chemical composition of tribolayers have been obtained by means of scanning electron microscope/energy dispersive spectroscopy to identify the dominant wear mechanism(s).The preliminary results have shown that the wear rate of boron steel decreased almost one order of magnitude as the temperature increased from room temperature to 300 °C. This behavior is consistent with the formation of a protective glaze layer initiated at 100°C. At higher temperatures, such layers become more extensive. The collected data was finally used to construct a wear map for this material pair that takes temperature into account.

  • 58.
    Hernandez, Sinuhe
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    High-Temperature Friction and Wear of Boron Steel and Tool Steel in Open and Closed Tribosystems2018Ingår i: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 61, nr 3, s. 448-458Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    More and more components in automotive, material processing and mining industries are operating under harsh conditions involving high temperatures and high contact pressures. Tribotesting for such applications is done using both open (one surface meeting a fresh counter-surface) and closed (one surface follows the same track on the counter-surface) test configurations. In order to enable development of new materials and processes intended for such conditions, there is a need for better understanding pertaining to tribological phenomena occurring under these different test configurations.

    In this work, friction and wear characteristics of quenched and tempered tool steel sliding against boron steel (22MnB5) have been studied. The experiments were conducted using a specially designed hot strip tribometer (HST) under dry conditions at R.T. and 400°C in open as well as closed configurations. Scanning electron microscopy/energy dispersive spectroscopy and X-ray techniques were carried out to analyse the worn surfaces. Additionally, the results from the closed test configuration were compared to previous tests carried out with the same materials and parameters using a pin-on-disk (POD) test rig. The results have shown that wear was reduced at higher temperatures as well as with repeated sliding on the same contacting surfaces (i.e. closed configuration) compared to those with open configuration. A good correlation of wear mechanisms and coefficient of friction between closed configuration tests and those carried out with the POD test rig was observed especially at 400°C.

  • 59.
    Hernandez, Sinuhe
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Winkelmann, Horst
    AC²T research GmbH - Austrian Center of Competence for Tribology, Viktor-Kaplan-Straße 2 D, 2700 Wiener Neustadt.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Influence of temperature on hardness and abrasive wear of hot forming tool steel and boron steel2013Konferensbidrag (Refereegranskat)
  • 60.
    Hernandez, Sinuhe
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Winkelmann, Horst
    AC²T research GmbH - Austrian Center of Competence for Tribology, Viktor-Kaplan-Straße 2 D, 2700 Wiener Neustadt.
    Ripoli, M. Rodriguez
    AC²T research GmbH - Austrian Center of Competence for Tribology, Viktor-Kaplan-Straße 2 D, 2700 Wiener Neustadt.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Influence of temperature on abrasive wear of boron steel and hot forming tool steels2015Ingår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 338-339, s. 27-35Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In many industrial applications the occurrence of abrasive wear results in failure and replacement of components. Examples of these applications are found in mining, mineral handling, agriculture, forestry, process and metalworking industry. Some of these applications also involve operation of relatively moving surfaces at elevated temperatures which increases the severity of wear. A typical example of high temperature wear phenomena is that of tool steels during interaction with boron steel in hot forming. Some studies have been carried out regarding the high temperature tribological behaviour of these materials but results pertaining to their high temperature three body abrasive behaviour have not been published in the open literature. In this work, the high-temperature three body abrasive wear behaviour of boron steel and two different prehardened tool steels (Toolox33 and Toolox44) was investigated using a high temperature continuous abrasion machine (HT-CAT) at different temperatures ranging from 20 °C to 800 °C using a load of 45 N and a sliding speed of 1 ms-1. The wear results were correlated to the hot hardness of the different materials measured by means of a hot hardness tester (HHT) at a load of 10 kgf. Scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS) techniques were used to characterise the worn surfaces. The hot hardness measurements of the three different materials showed a slight but continuous decrease of hardness from room temperature to 600 °C. At temperatures above 600 °C the hardness showed a sharp decrease. The wear rate of Toolox 44 was constant from 20 °C to 400 °C. On the other hand, Toolox33 and boron steel, showed a reduced wear rate from 20 °C to 400 °C attributed to an increased toughness and the formation of wear-protective tribolayers respectively. At higher temperatures (from 400 °C to 800 °C), the wear rate for these materials increased mainly due to a decrease in hardness and the occurrence of recrystallization processes.

  • 61. Lundmark, Jonas
    et al.
    Kassfeldt, Elisabet
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Prakash, Braham
    Influence of initial surface topography on tribological performance of the wheel/rail interface during rolling/sliding conditions2007Ingår i: High tech in heavy haul: Proceedings. International Heavy Haul Conference. Specialist Technical Session / [ed] Thomas Nordmark; Per-Olof Larsson-Kråik, Luleå: Luleå tekniska universitet, 2007, s. 673-680Konferensbidrag (Refereegranskat)
  • 62. Lundmark, Jonas
    et al.
    Kassfeldt, Elisabet
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Prakash, Braham
    The influence of initial surface topography on tribological performance of the wheel/rail interface during rolling/sliding conditions2009Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 223, nr 2, s. 181-187Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of surface roughness in a rail/wheel contact has been a concern for railway owners since the introduction of ‘rail grinding' as a maintenance strategy. Presently, there are no well-defined guidelines regarding the surface topographies of ground rails and re-turned wheels. There is thus a need to establish scientific guidelines regarding the surface topographies for the rails and wheels in order to minimize grinding costs/time and to improve rail/wheel performance. This study is aimed at investigating the influence of surface topographies of wheels and rails on running-in behaviour, wear, friction, and the resultant surface damage through experimental simulation in the laboratory. A two-disc rolling/sliding test machine has been used in this experimental work. Two different roughness values were produced on both the rail and wheel test specimens. A design of experiment approach has been used to conduct experiments and to analyse the results. The results show that the surface roughness values of the specimens in some material pairs do influence wear, friction, and resulting surface damage.

  • 63.
    Moghaddam, Pouria Valizadeh
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Vuorinen, Esa
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    The role of retained austenite in dry rolling/sliding wear of nanostructured carbide-free bainitic steels2019Ingår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 428-429, s. 193-204Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The dry rolling/sliding wear of nanostructured bainite has been investigated and compared with that of a conventional quenched and tempered bearing steel. In order to elucidate the role of retained austenite on the wear performance, high silicon hypereutectoid bearing steel with an identical alloy composition was heat treated to obtain different microstructures with similar hardness and different amounts of retained austenite. The results indicate that the nanostructured bainite can meet the minimum hardness requirements for bearing applications. Moreover, the nanostructured bainite outperformed the tempered martensitic steel in terms of wear resistance. The work hardening capacity and thus wear resistance increases due to the transformation of retained austenite into martensite. The results of XRD analyses show that the higher stability of retained austenite and strength of bainitic ferrite leads to better wear performance. It is demonstrated that the stability of retained austenite outweigh the influence of retained austenite content on wear resistance. Adhesion and oxidation were identified as the main wear mechanisms. In addition to microstructure, surface oxidation also plays a prominent role in determining the wear resistance. 

  • 64.
    Mozgovoy, Sergej
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Alik, Lotfi
    Luleå tekniska universitet.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Material transfer during high temperature sliding of Al-Si coated 22MnB5 steel against PVD coatings with and without aluminium2019Ingår i: Wear of Materials, Elsevier, 2019, Vol. 426-427, s. 401-411Konferensbidrag (Refereegranskat)
    Abstract [en]

    Press hardening of Al-Si coated 22MnB5 steel is the dominant technology to enable light weight design in automotive applications. Transfer of the Al-Si coating onto the tool surface occurs during hot forming. This affects process economy and quality of produced components. The reported galling mechanisms are adhesion and compaction of wear debris. Surface engineering of forming tools has been proposed to minimise the transfer of Al-Si coating. Plasma nitriding of tool steel surfaces reduces adhesion but has poor abrasive wear resistance. PVD coatings have generally been found to promote galling due to higher chemical affinity but improve abrasive wear resistance. Most studied PVD coatings are transition metal nitrides containing aluminium. The aim of this study is to investigate the role of aluminium in PVD coatings and its effect on transfer of Al-Si coating material during sliding against coated tool steel at high temperatures. This work has focussed on PVD coatings (AlCrN and CrWN) deposited on plasma nitrided tool steel. Their tribological behaviour was studied using a hot strip-drawing tribometer capable of simulating the conditions prevalent in press hardening. The results showed that PVD coatings containing aluminium induce more material transfer. The material transfer is mainly related to chemical affinity since all coatings were polished to a low surface roughness (Sa =~120 nm) to minimise transfer initiated by surface defects. The hardness of the PVD coatings does not seem to influence the material transfer since the softer coating (CrWN, HV0.05 = ~1850) showed less transfer compared to AlCrN (HV0.05 = ~2100). The CrWN coating showed longer running-in compared to AlCrN due to reduced initial material transfer. Formation of thicker transfer layers governs the steady state friction mechanisms. Material transfer of Fe-Al intermetallic compounds occurs at the initial stages of sliding through direct adhesion to the PVD coating. The layers grow to > 5 µm thickness within a few decimetres of sliding.

  • 65.
    Mozgovoy, Sergej
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Deng, Liang
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Effect of temperature on friction and wear of prehardened tool steel during sliding against 22MnB5 steel2013Konferensbidrag (Refereegranskat)
  • 66.
    Mozgovoy, Sergej
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Deng, Liang
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Effect of temperature on friction and wear of prehardened tool steel during sliding against 22MnB5 steel2014Ingår i: Tribology - Materials, Surfaces & Interfaces, ISSN 1751-5831, E-ISSN 1751-584X, Vol. 8, nr 2, s. 65-73Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mechanical components in tribological systems exposed to elevated temperatures are gaining increased attention since more and more systems are designed to operate under extreme conditions. In hot metal forming, the effect of temperature on friction and wear is especially important since it is directly related to process economy (tool wear) and quality of the produced parts (friction between tool and workpiece). This study is therefore focused on fundamental understanding pertaining to the tribological characteristics of prehardened hot work tool steel during sliding against 22MnB5 boron steel. The tribological tests were carried out using a high temperature reciprocating sliding friction and wear tester under a normal load of 31 N (corresponding to a contact pressure of 10 MPa), a sliding speed of 0·2 m s−1 and temperatures ranging from 40°C to 800°C. It was found that friction coefficient and specific wear rate decreased at elevated temperature because of formation of compacted wear debris layers on the surfaces.

  • 67.
    Mozgovoy, Sergej
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Deng, Liang
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Simulative High Temperature Friction and Wear Studies for Press Hardening Applications2015Ingår i: Hot Sheet Metal Forming of High-Performance Steel 5th International Conference: May 31-June 3, Toronto, Canada : Proceedings / [ed] Kurt Steinhoff; Mats Oldenburg; Braham Prakash, Auerbach: Verlag Wissenschaftliche Scripten , 2015, s. 167-175Konferensbidrag (Refereegranskat)
    Abstract [en]

    Press hardening is employed in automotive industry to produce advanced high-strength steel components for safety and structural applications. In this hot forming process, the dimensional accuracy of produced components relies not only on an optimum friction level for the deformation of the workpiece, but it also gets affected by wear of the forming tools, which reduces the service life of the tool as well. It is desirable to enhance the durability of the tools by understanding the influence of contact conditions on tool wear. However, this is difficult to achieve in conventional tribological testing equipment. With this in view, the tribological behaviour of tool-workpiece material pairs at elevated temperatures has been studied in a newly developed experimental set-up simulating the conditions prevalent during interaction of the hot workpiece with the tool surface. The coefficients of friction of uncoated and Al-Si coated 22MnB5 steel decreased when the normal load increased. The influence of sliding velocity on the coefficient of friction was negligible for uncoated and Al-Si coated 22MnB5 steel. In the case of Al-Si coated 22MnB5 steel, adhesive material transfer of the Al-Si coating onto the tool steel surface was the main wear mechanism and this was also the reason for the higher and unstable friction coefficient when compared to uncoated 22MnB5 steel. In the case of uncoated 22MnB5 steel, adhesion was the main wear mechanism.

  • 68.
    Mozgovoy, Sergej
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Deng, Liang
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Tribological Behavior of Tool Steel under Press Hardening Conditions Using Simulative Tests2018Ingår i: Journal of tribology, ISSN 0742-4787, E-ISSN 1528-8897, Vol. 140, nr 1, artikel-id 011606Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Press hardening is employed in the automotive industry to produce advanced high-strength steel components for safety and structural applications. This hot forming process depends on friction as it controls the deformation of the sheet. However, friction is also associated with wear of the forming tools. Tool wear is a critical issue when it comes to the dimensional accuracy of the produced components and it reduces the service life of the tool. It is therefore desirable to enhance the durability of the tools by studying the influence of high contact pressures, cyclic thermal loading, and repetitive mechanical loading on tool wear. This is difficult to achieve in conventional tribological testing devices. Therefore, the tribological behavior of tool-workpiece material pairs at elevated temperatures was studied in a newly developed experimental setup simulating the conditions prevalent during interaction of the hot sheet with the tool surface. Uncoated 22MnB5 steel and aluminum-silicon (Al-Si)-coated 22MnB5 steel were tested at 750 °C and 920 °C, respectively. It was found that higher loads led to lower and more stable friction coefficients independent of sliding velocity or surface material. The influence of sliding velocity on the coefficient of friction was only marginal. In the case of Al-Si-coated 22MnB5, the friction coefficient was generally higher and unstable due to transfer of Al-Si coating material to the tool. Adhesion was the main wear mechanism in the case of uncoated 22MnB5

  • 69.
    Mozgovoy, Sergej
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    High Temperature Friction and Wear Performance of PVD Coatings under Press Hardening Contact Conditions2019Ingår i: Advances in Tribology, ISSN 1687-5915, E-ISSN 1687-5923, Vol. 2019, artikel-id 4981246Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Press hardening is widely employed to produce automotive structural and safety components from advanced high-strength steels. This process depends on friction between the forming tools and the work piece. Wear of the forming tools affects the dimensional accuracy of produced components and reduces their service life. It is therefore desirable to reduce wear of forming tools for press hardening applications. One way to achieve this is by applying hard physical vapour deposited (PVD) coatings on the tool. In this work, the tribological behaviour of PVD coated tool-work piece material pairs has been studied at elevated temperatures in an experimental set-up simulating the tribological conditions in press hardening. Four different PVD coatings deposited on tool steel and uncoated tools as reference were studied during sliding against uncoated and Al-Si coated 22MnB5 steel. Results show that uncoated tools exhibited the lowest coefficient of friction when sliding against uncoated 22MnB5 steel. A CrWN coating initially showed low coefficient of friction but it increased with increasing sliding distance. A TiAlN coating and one of two AlCrN coatings showed similar frictional behaviour when sliding against uncoated 22MnB5 steel. During sliding against uncoated 22MnB5 steel, adhesive wear has been found to be the dominant wear mechanism. Adhesive wear was considerably reduced in the case of hard PVD coated tools in comparison to that of uncoated tools. During sliding against Al-Si coated 22MnB5 steel, no clear advantage in terms of friction behaviour of uncoated or PVD coated tools was observed. However, the transfer of Al-Si coating material from the work piece to the tools was significantly reduced for PVD coated tools. Frictional instabilities in all cases involving Al-Si coated work piece material further confirmed the occurrence of adhesive material transfer.

  • 70.
    Mozgovoy, Sergej
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    High Temperature Friction and Wear Studies on Tool Coatings under Press Hardening Contact Conditions2015Konferensbidrag (Refereegranskat)
  • 71.
    Pelcastre, Leonardo
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Courbon, Cedric
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Tribological behaviour of Al-Si-coated ultra-high-strength steel during interaction with tool steel at elevated temperatures: Influence of tool steel surface topography parameters on galling2015Ingår i: Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture, ISSN 0954-4054, E-ISSN 2041-2975, Vol. 229, nr 8, s. 1373-1384Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Galling is a severe form of adhesive wear encountered in metal forming operations. In hot stamping, an Al-Si coating is normally applied onto the ultra-high-strength steels to prevent decarburisation and to improve the corrosion resistance of the steel. Material transfer occurring from the coated ultra-high-strength steel to the tool surface has been identified as major issue in hot stamping. This transferred material impairs the quality of the produced parts and at the same time, it increases the costs of maintenance of the tools. This work focuses on the understanding of surface topography parameters and their effect on galling. Surface roughness level and orientation of the surface lay on tool surface have been studied. The results showed that a single parameter of the surface topography is not enough to describe the resistance to galling. Parameters such as Rv, Rp and Rsk are also important to consider in order to rank the galling resistance of the surface. The sliding direction with respect to the surface lay also had a significant influence on galling; sliding in the direction parallel to it resulted in substantially reduced material transfer.

  • 72.
    Pelcastre, Leonardo
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Herrera, Natlia
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Investigations into the failure mechanisms of form fixture hardening tools2011Ingår i: Proceedings, 3rd International Conference Hot Sheet Metal Forming of High Performance Steel: June 13 - 17, 2011, Kassel, Germany / [ed] Mats Oldenburg; Kurt Steinhoff; Braham Prakash, Auerbach: Verlag Wissenschaftliche Scripten , 2011, s. 93-103Konferensbidrag (Refereegranskat)
  • 73.
    Pelcastre, Leonardo
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Galling mechanisms during interaction of tool steel and Al-Si coated ultra-high strength steel at elevated temperature2013Ingår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 67, s. 263-271Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Occurrence of galling in hot forming is detrimental to the quality of produced parts and process economy. Material transfer from Al-Si coated work-piece to the tool material has been studied in this work. PVD coatings (AlCrN, TiAlN and DLC) on tool steel substrate have been considered as well as plasma nitriding and their tribological behaviour was compared to the case of an untreated tool steel. Galling initiates through accumulation and compaction of wear debris when untreated tools are used whereas the PVD coatings resulted in increased galling due to adhesion. Plasma nitrided tool steel showed negligible galling due to formation of glaze layers and the formation of such layers depends on the occurrence of wear of the nitrided tool steel.

  • 74.
    Pelcastre, Leonardo
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Influence of die Temperature on the Tribological Response During Interaction with Al-SI Coated Ultra-High Strength Steel2017Ingår i: 6th International Conference Hot Sheet Metal Forming of High-Performance Steel CHS2: June 4-7 2017, Atlanta, Georgia, USA : proceedings / [ed] Mats Oldenburg, Braham Prakash, Kurt Steinhoff, Warrendale, PA: Association for Iron & Steel Technology, AIST , 2017, s. 461-469Konferensbidrag (Refereegranskat)
  • 75.
    Pelcastre, Leonardo
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Influence of temperature on friction behaviour of tool steels sliding against Al-Si coated UHSS2016Ingår i: Proceedings of the 17th Nordic Symposium on Tribology : Nordtrib 2016, 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the automotive industry, a significant amount of components are formed using hot stamping. This process allows formation of complex shapes whilst controlling microstructure and mechanical properties of the end product. There are different tribological challenges encountered within the process due to the elevated temperature. The current studies focused on the tribological behaviour of different tool steels sliding against Al-Si coated steel (typically used in hot stamping) at different temperatures. It was observed that the tool steel temperature and the work-piece material temperature had a direct effect on friction level and stability and on the wear mechanisms; particularly in the occurrence of adhesive wear and material transfer onto the tool steels. In general, larger amount of material transfer and higher friction was observed with lower temperatures on the tool steel (~200˚C) and higher temperature of the work-piece material (~900˚C). The presence of oxides on the tool steel reduced the severity of material transfer and stabilised friction. However, the tool steel composition also affected the effectiveness in the stabilisation of the friction coefficient

  • 76.
    Pelcastre, Leonardo
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Influence of temperature on friction behaviour of tool steels sliding against Al-Si coated UHSS2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the automotive industry, a significant amount of components are formed using hot stamping. This process allows formation of complex shapes whilst controlling microstructure and mechanical properties of the end product. There are different tribological challenges encountered within the process due to the elevated temperature. The current studies focused on the tribological behaviour of different tool steels sliding against Al-Si coated steel (typically used in hot stamping) at different temperatures. It was observed that the tool steel temperature and the work-piece material temperature had a direct effect on friction level and stability and on the wear mechanisms; particularly in the occurrence of adhesive wear and material transfer onto the tool steels. In general, larger amount of material transfer and higher friction was observed with lower temperatures on the tool steel (~200˚C) and higher temperature of the work-piece material (~900˚C). The presence of oxides on the tool steel reduced the severity of material transfer and stabilised friction. However, the tool steel composition also affected the effectiveness in the stabilisation of the friction coefficient.

  • 77.
    Pelcastre, Leonardo
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Influence of tool steel surface topography on galling during hot forming of Al-Si coated ultra high-strength steels2012Ingår i: 15th Nordic Symposium on Tribology - NordTrib 2012: 12 - 15 June 2012 - Trondheim, Norway, Trondheim: Department of Geography, Norwegian University of Science and Technology, 2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Galling is a severe form of adhesive wear encountered in metal forming operations. In hot stamping, an Al-Si coating is normally applied onto the ultra high strength steels (UHSS) to prevent decarburisation and improve the corrosion resistance of the steel. Material transfer occurring from the coated UHSS to the tool surface has been identified as major issue in hot stamping. It is a known problem as this transferred material impairs the quality of the produced parts as well as increases the costs of maintenance of the tools. The present work focuses on the understanding of surface topography parameter and their effect on galling. Surface roughness level and orientation of the roughness marks (lay) on tool surface have been studied. The results showed that a single parameter of the surface topography is not enough to describe the resistance to galling. Parameters such as Rp, Rv and Rsk are also important to consider in order to rank the galling resistance of the surface. The sliding direction with respect to the surface lay also had a significant influence on galling; sliding in the direction parallel to it resulted in substantially reduced material transfer.

  • 78. Pelcastre, Leonardo
    et al.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Investigations into the occurrence of galling during hot forming of Al-Si coated high strength steel2010Konferensbidrag (Övrigt vetenskapligt)
  • 79.
    Pelcastre, Leonardo
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Investigations into the occurrence of galling during hot forming of Al-Si-coated high-strength steel2011Ingår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 225, nr 6, s. 487-498Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Galling is a severe form of adhesive wear associated with both cold and hot metal forming operations. In hot sheet metal forming of Al-Si-coated ultrahigh-strength steel (UHSS), transfer occurs from the coated UHSS to the tool surface. This leads to poor quality of produced parts, damage of expensive tooling, and increased downtime for maintenance of the tools. This study thus aims at identifying the salient mechanism(s), which give rise to initiation/occurrence of galling at elevated temperatures. This has been accomplished by analysing actual hot forming tools and through systematic parametric tribological investigations in the laboratory. The analysis of the actual tools has shown that the transferred layer consists of Al, Si, and Fe. The structure of the transferred materials is composed of sintered/compacted wear particles. The parametric study has shown that galling is dependent on the operating conditions. A strong relationship between the contact pressure and material transfer has been observed. The severity of galling is lower for smoother surfaces at low contact pressure. However, at high contact pressure, the influence of roughness under these conditions is insignificant. It has also been observed that hard-tool steel substrates reduce the severity of galling, particularly, at high contact pressure.

  • 80.
    Pelcastre, Leonardo
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Micro-mechanisms of galling at elevated temperatures2012Ingår i: International Colloquium Micro-Tribology 2012, Warsa, 2012, s. 29-30Konferensbidrag (Refereegranskat)
  • 81.
    Pelcastre, Leonardo
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Tribological behaviour of Zn coated UHSS sliding against hot-work tool steel at high temperatures2017Ingår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 376-377, nr Part-A, s. 423-432Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The increasing demands for light-weight components in vehicles contribute to the global expansion of hot sheet metal forming technologies. Structural components are typically produced using hot stamping of ultra-high strength steel (UHSS). This process allows forming of complex shapes whilst enabling control of the mechanical properties of the end product. Interest in zinc coated UHSS has increased in recent years in view of the corrosion protection it provides to the final components. There is a need for increased understanding of its tribological behaviour during the interaction with tool steel at elevated temperatures. In this work, tribological studies have been carried out in a novel hot strip tribometer. The aim was to study the effect of different operating conditions on the tribological behaviour of zinc coated UHSS sliding against a hot-work tool steel under un-lubricated conditions. The parameters studied in this work were; temperature, ranging from 400 °C to 700 °C; and contact pressure, from 5 to 30 MPa. The UHSS was initially heated up to austenitising temperature (840 °C) and then cooled down to the testing temperature. Upon stabilisation of temperature, the load was applied and sliding was carried out for a total of 1500 mm at 100 mm/s. The results showed a trend towards decreasing average coefficient of friction as temperature and contact pressure increased. Unstable friction behaviour was observed at low temperature (400 °C) and high contact pressure (30 MPa) whilst higher temperatures (600 °C) facilitated the development of a low and stable friction behaviour. It is proposed that the friction behaviour is controlled by the properties of the zinc phases in the coating developed during heating of the UHSS. The combination of high temperature and sliding conditions result in the removal of the uppermost oxide layer and the phases beneath control the friction behaviour.

  • 82.
    Pelcastre, Leonardo
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Rolland, Anthony
    Exchange Student LTU.
    Influence of microstructural evolution of Al-Si coated UHSS on its tribological behaviour against tool steel at elevated temperatures2014Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The usage of the hot stamping process is of great importance due tothe high demands for production of ultra-high strength steels (UHSS).An Al-Si coating is normally applied to the steel to preventdecarburisation and scaling during heating and to improve thecorrosion resistance of the final component. During heating, the Al andthe Si from the coating combine with the Fe from the steel substrate toform hard intermetallic phases. Little is known about the influence ofthe heating conditions on the tribological behaviour of the Al-Sicoating during interaction with tool steels. The present workinvestigated different heat treatment parameters and the influencethey had on the microstructure of the coating and the gallingbehaviour. With low alloying temperatures (700C), severe gallingoccurred and increasing the alloying temperature to 900C resulted inalmost negligible material transfer. The reduction in galling wasassociated to the development of Fe2Al5 and FeAl2 at the surface.

  • 83.
    Pelcastre, Leonardo
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Rolland, Anthony
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Influence of microstructural evolution of Al-Si coated UHSS on its tribological behaviour against tool steel at elevated temperatures2016Ingår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 228, s. 117-124Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The usage of the hot stamping process is of great importance due to the high demands for production of ultra-high strength steels (UHSS). An Al-Si coating is normally applied to the steel to prevent decarburisation and scaling during heating and to improve the corrosion resistance of the final component. During heating, the Al and the Si from the coating combine with the Fe from the steel substrate to form hard intermetallic phases. Little is known about the influence of the heating conditions on the tribological behaviour of the Al-Si coating during interaction with tool steels. The present work investigated different heat treatment parameters and the influence they had on the microstructure of the coating and the galling behaviour. With low alloying temperatures (700˚C), severe galling occurred and increasing the alloying temperature to 900˚C resulted in almost negligible material transfer. The reduction in galling was associated to the development of Fe2Al5 and FeAl2 at the surface.

  • 84.
    Pelcastre, Leonardo
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement. Division of Machine Elements, Luleå University of Technology.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement. Division of Machine Elements, Luleå University of Technology.
    Rolland, Anthony
    Division of Machine Elements, Luleå University of Technology.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement. Division of Machine Elements, Luleå University of Technology.
    Influence of microstructural evolution of Al-Si coated UHSS on its tribological behaviour against tool steel at elevated temperatures2014Ingår i: Society of Tribologists and Lubrication Engineers Annual Meeting and Exhibition 2014, Society of Tribologists and Lubrication Engineers , 2014, Vol. 1, s. 463-465Konferensbidrag (Refereegranskat)
    Abstract [en]

    In recent years, the usage of the hot stamping process has increased due to the high demands for production of ultra-high strength steels (UHSS). In particular, more studies are being carried out pertaining to the Al-Si coated UHSS to understand its behaviour during the forming process as well as the performance of the produced parts. The Al-Si coating is applied to the UHSS with the aim of reducing decarburisation and to avoid the formation of thick oxide scales on the work-piece during the heating stage. Usage of the Al-Si coating has the added benefit of greatly improving the corrosion resistance and paintability of the produced components [1,2].

  • 85.
    Pelcastre, Leonardo
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Vargas, Natalia Herrera
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Investigations into the damage mechanisms of form fixture hardening tools2012Ingår i: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 25, s. 219-226Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In metal forming operations such as form fixture hardening, the interaction between the tools and the work-piece is strongly influenced by the tribological properties at the interface. Damage or excessive wear of the tools can be detrimental to the quality of the final component and it also has an impact on the process economy due to increased maintenance or more frequent replacement of tools. The objective of this study was to investigate the damage mechanisms encountered in real form fixture hardening tools in order to understand the causes of tool failure and ultimately to come up with possible solutions for this problem.Advanced techniques such as Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) were used for obtaining an in-depth understanding of the different phenomena involved in the failure of form fixture hardening tools. Two different tools having different hardness values and microstructures that had been used in production were analysed.The damage mechanisms found included abrasive and adhesive wear, material transfer, corrosion and mechanical and thermal fatigue. The main damage mechanism was found to be cracking caused by mechanical stresses on the surface. Although both tools presented similar types of damage, the severity was different and it was strongly influenced by the microstructure.

  • 86.
    Pelcastre, Leonardo
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Heikkilä, Irma
    Swerea KIMAB, Stockholm.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    High Temperature Tribological Behaviour of Thermal-Spray Coated Toll Steels Sliding Against Al-Si Coated Ultra-High Strength Steel2017Ingår i: 6th International Conference Hot Sheet Metal Forming of High-Performance Steel CHS2: June 4-7 2017, Atlanta, Georgia, USA : proceedings / [ed] Mats Oldenburg, Braham Prakash, Kurt Steinhoff, Warrendale, PA: Association for Iron & Steel Technology, AIST , 2017, s. 223-232Konferensbidrag (Refereegranskat)
  • 87.
    Persson, Håkan
    et al.
    Bodycote Material Testing AB.
    Hjertsén, David
    Bodycote Material Testing AB.
    Waara, Patric
    SSAB Oxelösund AB.
    Prakash, Braham
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Nötningskorrosion: Utvärdering av nötnings- och korrosionsbeständiga material2007Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Rapporten beskriver en utvärdering av nötnings- och korrosionsbeständiga material för en transportskruv för avfallsbränsle i en typisk miljö vid avfallseldade CFB-pannor. Utprovning har genomförts i både kontrollerad laboratoriemiljö och i verklig miljö vilket har gett en bättre förståelse för vilka konstruktionsmaterial som lämpar sig bäst i denna tuffa miljö och gett en modell för att i framtiden bättre kunna prediktera slitagehastigheten. De förändrade driftförhållanden, framförallt lägre varvtal, som den nya transportskruven har medfört (installerad i februari 2007 och med vilken fältproven har genomförts) har förskjutit nötning/korrosion förhållandet så att korrosionen är mer dominerande i nötningskorrosionen. Detta är tydligt då SS 2377 (rostfritt duplext stål), som är det mjukaste av de utvärderade materialen, uppvisar lågt slitage till följd av sitt goda korrosionsmotstånd. Konstruktionen av skruven har visat sig vara väldigt avgörande för nötningskorrosion

  • 88.
    Prakash, Braham
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Courbon, Cedric
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    High temperature tribology research: needs and opportunities2013Konferensbidrag (Refereegranskat)
  • 89.
    Prakash, Braham
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Yang, Jun-Feng
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement. Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei.
    Fang, Qian-Feng
    Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei.
    Tribological properties of transition metal di-chalcogenide based lubricant coatings2012Ingår i: Frontiers of Materials Science, ISSN 2095-025X, E-ISSN 2095-0268, Vol. 6, nr 2, s. 116-127Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Transition metal di-chalcogenides MX 2 (X = S, Se, Te; and M = W, Mo, Nb, Ta) are one kind of solid lubricant materials that have been widely used in industry. The lubricant properties of such lubricant coatings are dependent not only on microstructure, orientation, morphology, and composition of the coatings, but also on the substrate, the interface between substrate and lubricant coatings, and the specific application environment. In this review, the effects of parameters on tribological properties of such kind of lubricant coatings were summarized. By comparing advantages and disadvantages of those coatings, the special treatments such as doping, structural modulation and post-treatment were suggested, aiming to improve the tribological performance under severe test conditions (e.g. high temperature, oxidizing atmosphere or humid condition).

  • 90.
    Prakash, Braham
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Pelcastre, Leonardo
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Galling in hot sheet forming of high strength steels2014Konferensbidrag (Refereegranskat)
  • 91.
    Prakash, Braham
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Pelcastre, Leonardo
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hot forming tribology2011Ingår i: Proceedings of 3rd European Conference on Tribology (ECOTRIB 2011) / [ed] Friedrich Franek; Wilfried J. Bartz; Andreas Pauschitz; Joze Vizintin; Enrico Ciulli; Rowena Crockett, Wien: The Austrian Tribology Society , 2011, s. 9-10Konferensbidrag (Refereegranskat)
  • 92.
    Renz, Alexander
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lehmann, Oliver
    Märkisches Werk GmbH, Research & Development Department, Halver 58553, Germany.
    High-temperature sliding wear behaviour of Stellite®12 and Tribaloy®T4002018Ingår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 402-403, s. 148-159Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, the sliding wear behaviour of the hardfacing alloys Stellite®12 and Tribaloy®T400 during interaction with a CrMo-steel is investigated at elevated temperatures. These materials are typically used for gas exchange valves and seat rings in large bore gas engines where they are subjected to severe operating conditions. The clean combustion and a decreased oil flow towards the tribosystem valve spindle/seat ring in the natural gas-fuelled engines cause excessive wear when operating at high combustion pressures and elevated temperatures.

    Commonly employed Co-based alloys for the valve seating faces show a vast variation in their wear behaviour when the high tribological loads act directly on the contact surfaces which are not protected by any type of tribofilm. In order to understand the mechanisms under unlubricated and metal-to-metal contact situation, reciprocating pin-on-disc sliding wear tests were carried out at high temperatures for the two common material combinations, mentioned above. The effects of temperature, initial hardfacing roughness, microstructure, and hardness on the friction and wear response are investigated. The quantitative wear results in combination with microstructural and wear mechanism analysis provide the foundation for a phenomenological description of the wear behaviour. The tendency to form oxides has been found to be a decisive factor in terms of the severity of wear of the investigated hardfacings. Stellite®12 shows low surface oxidation at elevated temperatures whereas the intermetallic phases in Tribaloy®T400 oxidize significantly.

  • 93.
    Syed, Abdul Khadar
    et al.
    Luleå tekniska universitet.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Pindtöödeldud ja järeloksüdeeritud tööriistateraste triboloogiline käitumine toatemperatuuril ning 400°C juures2010Ingår i: Estonian Journal of Engineering, ISSN 1736-6038, Vol. 16, nr 2, s. 123-134Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The primary focus of this investigation is on tribological properties of plasma nitrided and post-oxidized tool steels during sliding against ultra-high-strength boron steel. The experi­mental work has been carried out at room temperature and at 400 °C by using a high-temperature pin on disc tribometer. The experimental materials were tool steels of three different compositions, which were plasma nitrided and post-oxidized at 500 °C. One of the tool steels was also post-oxidized at 480 and 520 °C. The results have shown that the friction and wear characteristics are influenced by the test temperature and the post-oxidizing temperature. The tool steel, post-oxidized at 500 °C, resulted in better friction and wear performance at room temperature and also improved wear resistance at elevated temperature. The observed wear mechanisms are mainly adhesive at room temperature and a combination of adhesive and abrasive at elevated temperature.

  • 94. Syed, Abdul Khadar
    et al.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Tribological behaviour of surface treated and post-oxidised tool steels at elevated temperatures2009Konferensbidrag (Övrigt vetenskapligt)
  • 95.
    Yang, JunFen
    et al.
    Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei.
    Jiang, Yan
    Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Fang, Qianfeng
    Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei.
    Influence of service temperature on tribological characteristics of self-lubricant coatings: a review2013Ingår i: Frontiers of Materials Science, ISSN 2095-025X, E-ISSN 2095-0268, Vol. 7, nr 1, s. 28-39Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Self-lubricating coatings have been widely used to reduce friction in moving machine assemblies. However, the tribological performance of these coatings is strongly dependent on the service temperature. In this paper, an extensive review pertaining to the influence of operating service temperature on tribological performance of self-lubricating coatings has been carried out. Based on the effective lubricating temperature range, the self-lubricating coatings developed in the past have been divided into three groups: low temperature lubricant coating (from -200°C to room temperature), moderate temperature lubricant coating (from room temperature to 500°C) and high temperature lubricant coating (> 500°C). Ideas concerning possible ways to extend the operating temperature range of self-lubricating coatings have been presented as follows: hybridized tribological coating, adaptive tribological coatings, and diffusion rate limited solid lubricant coating. In addition, a new self-lubricating coating formulation for potential application at a wide operating temperature range has been proposed.

  • 96.
    Zhmud, Boris
    et al.
    Applied Nano Surfaces.
    Åkerlund, Eva-Brita
    Department of Engineering Sciences, Uppsala University.
    Jacobsson, Staffan
    Department of Engineering Sciences, Uppsala University.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hammerström, Lars
    Scania CV AB, Materials Technology.
    Ohlsson, Robert
    Volvo Powertrain.
    ANS triboconditioning: in-manufacture running-in process for improving tribological properties of mechanical parts made of steel or cast iron2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Component rig tests suggest that ANS triboconditioning brings significant improvements in the tribological properties of camshafts, cylinder liners, and rocker arm shafts. Extreme-pressure mechanical treatment of the component surface in combination with a tribochemical deposition of a low-friction antiwear film based on tungsten disulfide allows one to produce, in a single finishing operation, a smoother surface with a significantly reduced coefficient of boundary friction and improved wear-resistance and load-carrying capacity. The treatment proved to be especially efficient for reducing friction and wear in lubricated contacts under high tribological stress.

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