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  • 201.
    Prakash, Braham
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Pelcastre, Leonardo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hot forming tribology2011In: 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, p. 9-10Conference paper (Refereed)
  • 202. Prakash, Braham
    et al.
    Sandhu, H. S.
    Kalia, S. K.
    Awasthy, K. L.
    Indian Institute of Technology, New Delhi.
    Tribological performance of PTFE and its composites under different environmental conditions1991In: Industrial tribology: 9th National conference : Selected papers and discussions, CMTI , 1991, p. M33-M42Conference paper (Refereed)
  • 203. Prakash, Braham
    et al.
    Singh, J. V.
    Indian Institute of Technology, New Delhi.
    Reza, S. S.
    Indian Institute of Technology, New Delhi.
    A tribological study on an energy saving additive1991In: Industrial tribology: 9th National conference : Selected papers and discussions, CMTI , 1991, p. L87-L97Conference paper (Refereed)
  • 204. Prakash, Braham
    et al.
    Vankar, Vasant D.
    Indian Institute of Technology, New Delhi.
    Abrasive wear behaviour of some Fe‑based and Ni‑based metallic glasses1991In: Journal of Advanced Science, ISSN 0915-5651, Vol. 3, no 2, p. 64-68Article in journal (Refereed)
  • 205. Prakash, Braham
    et al.
    Wani, M. F.
    Indian Institute of Technology, New Delhi.
    Mukerji, J.
    Central Glass and Ceramic Research Institute (CGCRI), Calcutta.
    Das, P. K.
    Central Glass and Ceramic Research Institute (CGCRI), Calcutta.
    Tribological studies of hot pressed silicon nitride and composites1990In: 3rd International tribology conference: Selected papers, Tokyo: Japan Society of Tribologists , 1990, Vol. III, p. 1383-1388Conference paper (Refereed)
  • 206.
    Pujante, J.
    et al.
    Fundació CTM Centre Tecnològic, Avda.
    Pelcastre, Leonardo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Vilaseca, M.
    Fundació CTM Centre Tecnològic, Avda.
    Casellas, D.
    Fundació CTM Centre Tecnològic, Avda.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Investigations into wear and galling mechanism of aluminium alloy-tool steel tribopair at different temperatures2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 308, no 1-2, p. 193-198Article in journal (Refereed)
    Abstract [en]

    Aluminium alloys show poor formability at room temperature, and the production of complex components requires a series of high temperature forming processes, such as warm and hot forging, extrusion and hot sheet metal forming. Forming aluminium in these conditions subjects the tools to severe adhesive wear and galling, leading to increased energy needs, shorter tool life, lower part quality and increased cost. In this work, the wear mechanisms generated by aluminium alloys on forming tools have been studied by means of linear reciprocating sliding tests. Aluminium alloy AA2017 balls were slid against DIN 1.2344 (AISI H13) tool steel samples with various surface finishes at temperatures up to 450 °C. The main results show that the observed wear mechanisms are extremely dependent on the system temperature, ranging from pure abrasive wear to formation of layers of compacted aluminium debris and gross aluminium transfer in the form of lumps. On the other hand, tool surface finish has a limited effect on gross material transfer, but does affect the material transfer micromechanisms

  • 207.
    Pujante, Jaume
    et al.
    Fundació CTM Centre Tecnològic.
    Pelcastre, Leonardo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Vilaseca, Montserrat
    Fundació CTM Centre Tecnològic.
    Casellas, Daniel
    Fundació CTM Centre Tecnològic / Universitat Politècnica de Catalunya.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Investigations into wear and galling mechanism of aluminium alloy-tool steel tribopair at different temperatures2012In: 15th Nordic Symposium on Tribology - NordTrib 2012: 12 - 15 June 2012 - Trondheim, Norway, Trondheim: Department of Geography, Norwegian University of Science and Technology, 2012Conference paper (Refereed)
    Abstract [en]

    Aluminium-based alloys present a number of interesting properties, such as lower density, corrosion resistance, thermal and electrical conductivity and good recyclability. For this reason, there is a strong trend in increasing the use of these alloys, particularly in the automotive industry [1, 2]. However, aluminium alloys show poor formability at room temperature, and the production of complex components requires a series of high temperature forming processes, such as warm and hot forging, extrusion and hot sheet metal forming [3]. Forming aluminium in these conditions subjects the tools to severe adhesive wear and galling, leading to increased energy needs, shorter tool life, lower part quality and increased cost.In this work, the wear mechanisms generated by aluminium alloys on forming tools have been studied by means of linear reciprocating sliding tests, performed in an Optimol SRV equipment. Balls of two different compositions (AA2017 and 99% pure aluminium) were slid against DIN 1.2344 (AISI H13) tool steel samples with various surface finishes at temperatures up to 450 ºC. The resulting wear tracks were studied by means of confocal microscopy and electron microscopy (SEM/BSE).The main results show that the observed wear mechanisms are extremely dependent on the system temperature, ranging from pure abrasive wear to formation of layers of compacted aluminium debris and gross aluminium transfer in the form of lumps. The choice of aluminium alloy can be very relevant on the wear behaviour of the system. On the other hand, tool surface finish has a limited effect on material transfer. [1] Miller W S, et al. Recent development of aluminium alloys for the automotive industry. Materials Science and Engineering A 280 (2000), pp 37-49 [2] Toros S, Ozturk F, Kacar I. Review of warm forming of aluminium-magnesium alloys. Journal of Materials Processing Technology 207 (2008), pp 1-12[3] Hanna M D. Tribological evaluation of aluminium and magnesium sheet forming at high temperatures. Wear 267 (2009), pp 1046-1050

  • 208.
    Renz, Alexander
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Lehmann, Oliver
    Märkisches Werk GmbH, Research & Development Department, Halver 58553, Germany.
    High-temperature sliding wear behaviour of Stellite®12 and Tribaloy®T4002018In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 402-403, p. 148-159Article in journal (Refereed)
    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.

  • 209.
    Sethuramiah, A.
    et al.
    Indian Institute of Technology, New Delhi.
    Awasthy, K. L.
    Indian Institute of Technology, New Delhi.
    Prakash, Braham
    Mahapatra, P. K.
    Indian Institute of Technology, New Delhi.
    Lubricated wear of PTFE and graphited PTFE1991In: Lubrication Science, ISSN 0954-0075, E-ISSN 1557-6833, Vol. 3, no 3, p. 181-188Article in journal (Refereed)
    Abstract [en]

    Tribological behaviour of PTFE and graphited PTFE have been evaluated under lubricated conditions and compared with dry wear. The stress selected is in the range of 0.44 to 1.64 MPa, and the data generated are relevant to conformal contacts. Mineral oil lubrication can reduce wear of PTFE by one to two orders of magnitude. With graphited PTFE the lubricant effect is lower in comparison to that observed with PTFE. Specific wear rates are plotted on a histogram.

  • 210.
    Sharma, P. K.
    et al.
    University Medical Center Groningen.
    Mei, Henny C. van der
    University Medical Center Groningen.
    Busscher, Henk J.
    University Medical Center Groningen.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribology of hetero-polymeric conditioning films: the role of Vroman effect2009In: Proceedings of the World Tribology Congress 2009: Sunday 6th to Friday 11th, September, 2009, Kyoto, Japan, Tokyo: Japan Society of Tribologists , 2009, p. 643-Conference paper (Other academic)
  • 211.
    Sharma, Vinay
    et al.
    University of Texas, Arlington, Department of Material Science & Engineering.
    Johansson, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Timmons, Richard B.
    University of Texas, Arlington, Department of Chemistry & Biochemistry.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Aswath, Pranesh B.
    University of Texas, Arlington, Department of Material Science & Engineering.
    Tribological Interaction of Plasma-Functionalized Polytetrafluoroethylene Nanoparticles with ZDDP and Ionic Liquids2018In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 66, no 3, article id 107Article in journal (Refereed)
    Abstract [en]

    Polytetrafluoroethylene (PTFE) nanoparticles were coated with consecutive plasma deposited siliceous and methacrylate coatings. Secondary zinc dialkyldithiophosphate (ZDDP), phosphonium cation and phosphate anion ionic liquid (IL), and IL with phosphonium cation and dithiophosphate anion were mixed with the functionalized nanoparticles. Tribological studies were carried out for seven separate formulations including base oil, oils with only additives, and oils with additives and functionalized PTFE particles. Results indicate strong synergistic interactions of ZDDP and ILs with functionalized nanoparticles providing enhanced friction and wear performance. Chemical analysis of the tribofilms using X-ray photoelectron spectroscopy and X-ray absorption near edge structure spectroscopy indicates functionalized PTFE nanoparticles interact synergistically with ZDDP and ILs to form silicon- and fluorine-doped tribofilms resulting in superior tribological performance.

  • 212.
    Simmons, Gregory F
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Glavatskih, Sergei
    Machine Design, Royal Institute of Technology.
    Mûller, Michael
    Evonik RohMax Additives GmbH, 64293 Darmstadt.
    Byheden, Åke
    Statoil Lubricants, Nynäshamn.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Extending performance limits of turbine oils2014In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 69, p. 52-60Article in journal (Refereed)
    Abstract [en]

    New turbine oils providing both extremely high viscosity index (VI) and improved boundary/mixed lubrication performance are investigated. Comparisons are made in both laboratory scale testing using typical journal bearing sliding surfaces (steel and white metal) and full scale testing using a hydrodynamic journal bearing test machine. The results from these studies demonstrate the effectiveness of new, high VI, turbine oils for reducing friction at machine startup and improving performance during full film operation.

  • 213.
    Simmons, Gregory F
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Glavatskih, Sergei
    Machine Design, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden.
    Schweder, Roland
    Evonik RohMax Additives GmbH, 64293 Darmstadt.
    Byheden, Åke
    Statoil Lubricants.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Extending performance limits of turbine oils2012In: 15th Nordic Symposium on Tribology - NordTrib 2012: 12 - 15 June 2012 - Trondheim, Norway, Trondheim: Department of Geography, Norwegian University of Science and Technology, 2012Conference paper (Refereed)
    Abstract [en]

    New lubricants providing both extremely high viscosity index (VI) and improved boundary/mixed lubrication performanceare investigated. Comparisons are made in both laboratory scale testing using typical journal bearing slidingsurfaces (steel and white metal) and full scale testing using a hydrodynamic journal bearing test machine. The resultsfrom these studies demonstrate the effectiveness of new, high VI, turbine oils at reducing friction at machine startupand improving performance during steady state operation.

  • 214. Simmons, Gregory F
    et al.
    Mofidi, Mohammadreza
    Department of Mechanical Engineering, Shahid Bahonar University, Kerman.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Friction evaluation of elastomers in lubricated contact2009In: Lubrication Science, ISSN 0954-0075, E-ISSN 1557-6833, Vol. 21, no 10, p. 427-440Article in journal (Refereed)
    Abstract [en]

    Friction testing of elastomers in lubricated contact is discussed with a focus on developing experimental arrangements that can produce worthwhile results. Practical issues unique to elastomers are covered as well as their solutions, including contact mechanics, material response to loading, contact edges, oil absorption, cleaning and specimen geometry. A critique of reciprocating laboratory testing machines, including high-frequency short stroke and low-frequency long stroke friction and wear machines, is conducted for their usefulness, as is critical analysis of a wide variety of specimen configurations with the aim of helping the laboratory experimenter to overcome many of the pitfalls associated with testing of elastomers in lubricated conditions. Results from experiments using various testing arrangements are analysed, and it is found that the synthetic ester and mineral oil used produced similar results.

  • 215.
    Steihoff, Kurt
    et al.
    University of Kassel.
    Oldenburg, MatsLuleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.Prakash, BrahamLuleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hot sheet metal forming of high-performance steel: Proceedings of the 1st International Conference, Kassel, Germany, October 22-24, 20082008Collection (editor) (Other academic)
  • 216.
    Syed, Abdul Khadar
    et al.
    Luleå tekniska universitet.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Pindtöödeldud ja järeloksüdeeritud tööriistateraste triboloogiline käitumine toatemperatuuril ning 400°C juures2010In: Estonian Journal of Engineering, ISSN 1736-6038, Vol. 16, no 2, p. 123-134Article in journal (Refereed)
    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.

  • 217. Syed, Abdul Khadar
    et al.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Tribological behaviour of surface treated and post-oxidised tool steels at elevated temperatures2009Conference paper (Other academic)
  • 218.
    Taghipour, Ali
    et al.
    Sintef Petroleum AS.
    Ytrehus, Jan David
    Sintef Petroleum AS.
    Lund, Bjørnar
    Sintef Petroleum AS.
    Skalle, Pål
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Lund, Martin
    Luleå University of Technology, Professional Support, Centralverkstaden.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Friction and wear characteristics of steel on rock under water and oil based lubricated sliding conditions2015In: Tribology - Materials, Surfaces & Interfaces, ISSN 1751-5831, E-ISSN 1751-584X, Vol. 9, no 2, p. 85-91Article in journal (Refereed)
    Abstract [en]

    In recent years, drilling extended reach wells have become more and more common in the petroleum industry to optimise the oil and gas production. Extended reach wells are defined as wells that have two times more horizontal step out than true vertical depth. High friction (frictional torque) and drag are two of the mechanical limiting factors while drilling longer horizontal wellbores. There are numerous methods and tools developed to lower the drillstring friction. Drilling non-circular wellbores is a new concept with potential to minimise the mechanical friction by reducing drillstring and sidewalls contact area. However, this will cause an increase of contact pressure owing to the reduced contact area between drillstring and the formation. This article presents results obtained from an experimental study pertaining to the friction behaviour using a pin on disc set-up with steel pin and granite disc in the presence of water and oil based lubricants. These tests have been designed to represent frictional contact conditions between a rotating steel drillstring and the wellbore wall at different contact pressures. Test results show that the friction coefficient decreases with an increase of contact pressure in wet condition for both water and oil based lubricants. It is also observed that the friction factor increased by adding sand and phyllite particles to the water based lubricant. Considering the wear scars, the friction coefficient shows reduction with increased contact pressure in all tests with and without particles for both water and oil based lubricants.

  • 219.
    Tomala, A.
    et al.
    AC²T research GmbH - Austrian Center of Competence for Tribology, Viktor-Kaplan-Straße 2 D, 2700 Wiener Neustadt.
    Hernandez, Sinuhe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Ripoli, M. Rodriguez
    AC²T research GmbH - Austrian Center of Competence for Tribology, Viktor-Kaplan-Straße 2 D, 2700 Wiener Neustadt.
    Badisch, E.
    AC²T research GmbH - Austrian Center of Competence for Tribology, Viktor-Kaplan-Straße 2 D, 2700 Wiener Neustadt.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribological performance of some solid lubricants for hot forming through laboratory simulative tests2014In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 74, p. 164-173Article in journal (Refereed)
    Abstract [en]

    Tribological research concerning sliding contacts at temperatures of 500–1000 °C has received limited attention. Industrial systems operating under high temperatures can be readily found in sheet metal forming processes. The control of friction during the tool-workpiece interaction and minimization of tool wear are both crucial in maintaining the products quality. The application of solid lubricants can be a possible approach in accomplishing these goals.The objective of this work is to investigate the reliability of combined model and component tests under solid lubricating conditions. The laboratory tests showed that both methodologies provide consistent results in exploring potential of the solid lubricants

  • 220.
    Torres, Hector
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. AC2T Research GmbH, Wiener Neustadt, Austria.
    Caykara, Tugce
    Rojacz, H.
    AC2T Research GmbH, Wiener Neustadt, Austria.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Rodríguez Ripoll, M.
    AC2T Research GmbH, Wiener Neustadt, Austria.
    The tribology of Ag/MoS2-based self-lubricating laser claddings for high temperature forming of aluminium alloys2020In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 442, article id 203110Article in journal (Refereed)
    Abstract [en]

    In recent years, the use of aluminium alloys in the automotive industry has gained significant attention due to their specific strength, corrosion resistance and recyclability. However, their forming at high temperature in processes like hot stamping is challenging due to the poor tribological behaviour of aluminium alloys, which is the source of severe adhesive wear and a poor surface quality of the finished product.

    In an effort to overcome these tribological problems, iron- and nickel-based self-lubricating laser claddings with the addition of solid lubricants such as silver and molybdenum disulfide have been evaluated under conditions representative of hot stamping against the aluminium alloy AA6082. It has been found that self-lubricating claddings decrease friction and counter body wear at high temperatures compared to alloys commonly used in forming tools such as grade 1.2367 steel. Furthermore, nickel-based self-lubricating claddings have shown a better tribological behaviour than their iron-based counterparts, due to the formation of a nickel-based sulfide layer on the counter body. It is thus expected that the implementation of self-lubricating claddings can improve the quality of the final product while reducing the need for added lubricant during the hot stamping of aluminium alloys.

  • 221.
    Torres, Hector
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. AC2T research GmbH, Wiener Neustadt, Austria.
    Rodriguez Ripoll, M.
    AC2T research GmbH, Wiener Neustadt, Austria.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Self-lubricating laser claddings for friction control during press hardening of Al-Si-coated boron steel2019In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 269, p. 79-90Article in journal (Refereed)
    Abstract [en]

    In recent years, the use of Al/Si coatings has become widespread in hot stamping in order to protect the work piece from detrimental mechanisms such as scale formation or decarburisation affecting the quality of the finished product. However, the formation of Al-Fe intermetallics due to diffusion at high temperature can lead to unstable friction and damage both the tool and the work piece.

    In the present study, self-lubricating coatings with the addition of silver and MoS2 have been prepared by means of laser cladding deposition, aiming at their use in hot stamping in order to decrease friction and wear. The coatings were evaluated at high temperatures against Al-Si-treated boron steel using two different testing configurations featuring open and closed tribosystems. A significant reduction in friction for the self-lubricating claddings were observed along with decreased material transfer. This could be beneficial for hot stamping applications as it can ensure the stability of the process while preventing surface damage to the work piece. Additionally, closed configuration tribotesting has been found to underestimate friction and wear of the tool/work piece system, thus making it less suited for the lab-scale simulation of hot metal forming compared to open configuration tribometers. This finding has been considered relevant as many references in the available literature still report the use of closed configuration tribometers.

  • 222.
    Torres, Hector
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. AC2T Research GmbH, Wiener Neustadt, Austria.
    Rodríguez Ripolla, Manel
    AC2T Research GmbH, Wiener Neustadt, Austria.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribological behaviour of self-lubricating materials at high temperatures2018In: International Materials Reviews, ISSN 0950-6608, E-ISSN 1743-2804, Vol. 63, no 5, p. 309-340Article in journal (Refereed)
    Abstract [en]

    Self-lubricating materials are becoming more widespread in fields like metal forming or power generation due to the inability to use conventional lubricants in high-temperature (HT) applications. In an effort to summarise the progress done in this field, a detailed literature review has been carried out, ranging from micron-thickness thin films to hardfacings and bulk materials, and classified by the reported solid lubricants. Moreover, the most-cited deposition techniques have been reviewed for each lubricant class in addition to their advantages and limitations. HT friction and wear data for self-lubricating materials have also been examined in order to identify effective lubrication ranges and general trends in their tribological behaviour, which is expected to be useful for researchers interested in this field. Finally, several apparent research gaps have been described, with suggestions for new experimental work that could lead to the development of new high-temperature self-lubricating materials.

  • 223.
    Torres, Hector
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. AC2T Research GmbH.
    Slawik, Sebastian
    Saarland University, Department of Materials Science and Engineering.
    Gachot, Carsten
    Technische Universität Wien, Department of Engineering Design and Logistics Engineering, Vienna.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Rodríguez Ripoll, Manel
    AC2T research GmbH.
    Microstructural design of self-lubricating laser claddings for use in high temperature sliding applications2018In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 337, p. 24-34Article in journal (Refereed)
    Abstract [en]

    Nickel-based self-lubricating claddings with the addition of Ag and MoS2 were prepared by means of laser cladding on stainless steel substrates, aiming at their implementation in metal forming applications involving demanding tribological conditions at high temperatures. The novelty of this approach is the addition of MoS2 with the aim to achieve a uniform silver distribution within the resulting cladding by means of an encapsulation mechanism. This prevents it from floating to the surface during the deposition process and thus being subsequently lost during surface preparation. The role of Ag and MoS2 concentration on the encapsulation process is discussed in terms of phase composition and resulting microstructures. The tribological behaviour of the resulting laser claddings was evaluated at up to 600 °C under unidirectional sliding. The encapsulation of Ag leads to outstanding tribological properties while keeping the concentration of used Ag low, thus increasing the economic viability of the claddings. An improvement in terms of both friction and wear was observed for the self-lubricating claddings compared to the nickel-based reference alloy, thus making them good candidates for use in high temperature applications such as hot metal forming.

  • 224.
    Torres, Hector
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. AC2T Research GmbH.
    Vuchkov, T.
    AC2T Research GmbH.
    Rodríguez Ripoll, Manel
    AC2T research GmbH.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribological behaviour of MoS2-based self-lubricating laser cladding for use in high temperature applications2018In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 126, p. 153-165Article in journal (Refereed)
    Abstract [en]

    Many high temperature (HT) forming processes require the use of solid lubricants in order to control friction and reduce wear. In an attempt to eliminate the need for solid lubrication in high temperature sliding applications, nickel-based self-lubricating coatings with the addition of Ag and MoS2 were prepared by means of laser cladding on stainless steel substrates.

    The behaviour of the resulting laser claddings was thoroughly evaluated up to 600 °C, including the oxidation behaviour and reciprocating tribotesting using different counter body geometries (ball and flat pin). The self-lubricating coatings showed lower friction than the unmodified reference alloy at all tested temperatures, in addition to a significant microstructural stability after prolonged exposure at high temperatures. The addition of solid lubricants to the claddings was also found to be beneficial in terms of the counter body wear at HT, as no material loss could be measured for the bearing balls after testing at 600 °C against the self-lubricating claddings, despite the significant softening experienced by AISI 52100 bearing steel at HT.

  • 225.
    Torres, Hector
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. AC2T research GmbH.
    Vuchkov, Todor
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Slawik, Sebastian
    Saarland University, Department of Materials Science and Engineering.
    Gachot, Carsten
    Technische Universität Wien, Department of Engineering Design and Logistics Engineering, Vienna.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Rodríguez Ripoll, Manel
    AC2T research GmbH.
    Self-lubricating laser claddings for reducing friction and wear from room temperature to 600 °C2018In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 408-409, p. 22-33Article in journal (Refereed)
    Abstract [en]

    In this work, laser cladding has been employed for the preparation of nickel-based self-lubricating coatings featuring the addition of different combinations of soft metal solid lubricants such as Ag and Cu. Transition metal dichalcogenides (WS2, MoS2) were evaluated as precursors for encapsulating and uniformly distributing the soft metals throughout the microstructure. The tribological behaviour of the resulting claddings was evaluated under high temperature reciprocating sliding conditions, including two different counter body geometries that lead to very different ranges of contact pressures during testing. An improved tribological behaviour was observed for the self-lubricating claddings compared to the unmodified nickel-based alloy up to 600 °C, attributed to the presence of silver and the formation of lubricous sulfides during sample preparation due to the thermal degradation of the transition metal dichalcogenides precursors. Additionally, the role of the contact conditions observed when testing the self-lubricating claddings against flat pins instead of spherical counter bodies are discussed in terms of frictional and wear microstructural mechanisms.

  • 226.
    Ukonsaari, Jan
    et al.
    Vattenfall Research & Development.
    McCarthy, Donald
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hedström, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Tribological studies on an EAL lubricated bearing bronze - steel pair under reciprocating sliding conditions2008In: Tribologia : Finnish Journal of Tribology, ISSN 0780-2285, Vol. 27, no 1, p. 3-18Article in journal (Refereed)
    Abstract [en]

    Boundary lubricated journal bearings are found in various applications involving oscillatory sliding conditions. Environmental adaptation of hydraulic systems includes the introduction of synthetic esters. These new environmentally adapted lubricants (EALs) have shown very good boundary lubrication performance but also condition sensitivity. This study examines an oil lubricated bronze pin on hardened steel configuration in a reciprocating friction and wear test machine. Three synthetic esters were tested with a 1 mm stroke length. Results were compared with those for a mineral oil. The tribological performance with synthetic ester lubricant can, under certain conditions, be very good. SEM-EDS and XRD surface sensitive studies indicate the formation of a soft, copper enriched outer contact layer. The layer's nature and contact mechanisms clearly affect the performance of the different lubricants. (17 refs.)

  • 227.
    Vuorinen, Esa
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Pino, David
    Luleå tekniska universitet.
    Lundmark, Jonas
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Wear characteristics of surface hardened ausferritic Si-steel2007In: Journal of Iron and Steel Research International, ISSN 1006-706X, E-ISSN 2210-3988, Vol. 14, no 1, supp 1, p. 245-248Article in journal (Refereed)
    Abstract [en]

    High strength steels can be produced by austempering of Si-containing steels. It is possible to achieve high toughness and good wear resistance in these steels. Surface hardening of this group of steels can further increase the surface hardness and wear resistance and in combination with high strength in the bulk, also the fatigue strength. Surface hardening by laser-hardening has been performed on steel 55Si7 after austempering of the steel in order to create a ferritic-austenitic carbide free microstructure. Tempering effects and hardness values have been studied. Optical as well as scanning electron microscopy has been used together with x-ray diffractometry in the characterization of the micro-structural changes. Wear resistance testing of austempered and laser hardened samples respectively of the Si-alloyed steel have been reported and also compared with that of the conventional Cr-alloyed steel. The results of the specific phase transformation from austenite to martensite during wear process will be reported

  • 228.
    Vuorinen, Esa
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Wang, Lin
    Luleå tekniska universitet.
    Stanojevic, Sanja
    Luleå tekniska universitet.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Influence of retained austenite on rolling-sliding wear resistance of austempered silicon alloyed steel2009In: Hot sheet metal forming of high-performance steel, CHS2: 2nd international conference, June 15-17 2009, Luleå, Sweden. Proceedings / [ed] Mats Oldenburg; Kurt Steinhoff; Braham Parkash, Auerbach: Verlag Wissenschaftliche Scripten , 2009, p. 339-347Conference paper (Refereed)
  • 229. Waara, Patric
    et al.
    Norrby, Thomas
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribochemical wear of rail steels lubricated with synthetic ester-based model lubricants2004In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 17, no 3, p. 561-568Article in journal (Refereed)
    Abstract [en]

    Headchecks are a common type of damage in heavily loaded curved freight tracks. This paper deals with synthetic ester formulations' ability to prevent damage caused by headchecks through mild tribochemical wear. An experimental study pertaining to wear and friction of two rail steels lubricated by two synthetic ester base fluids, TMP-oleate and TMP-C8-C10, has been carried out. Six different free fatty acids were used in this study to act as performance additives. Three of the fatty acids were mono-acids with different, straight, carbon chain lengths (stearic acid C18, decanoic acid C10 and octanoic acid C8), one was a mono-unsaturated straight-chain fatty acid (oleic acid C18:1) while two were dibasic acids with intermediate carbon chain length (C9 and C10). Each fatty acid was blended with either ester, one at a time. The tests were carried out by using a high frequency reciprocating friction and wear test machine. In these tests, the gage face/wheel flange contact was simulated, and all tests were conducted in the boundary lubrication regime. An initial contact pressure of 316 MPa and a maximum sliding speed of 0.11 m/s were employed during the tests. The tests showed a wide range of wear rates, as well as different surface features depending on the interactions between synthetic esters, fatty acids and steel. The use of stearic and azaleic acid in lubricating rail steels results in very smooth surfaces with significant differences in their wear rates.

  • 230.
    Wang, Zhou
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Temperature dependent changes of physicochemical and tribological properties of NBR elastomer upon ageing in hexadecane and DGDE2012In: 15th Nordic Symposium on Tribology - NordTrib 2012: 12 - 15 June 2012 - Trondheim, Norway, Trondheim: Department of Geography, Norwegian University of Science and Technology, 2012Conference paper (Refereed)
    Abstract [en]

    Acrylonitrile-butadiene rubber (NBR) elastomers are widely used in seal and tire industries. Physiochemical, surface and tribological properties of NBR exposed to a lubricant in a sealed mechanical contact may gradually change, in particular, at elevated temperatures. In this study, industrial-grade NBR elastomers were aged in two model non-additivated base oils, namely non-polar hexadecane (HEX) and polar Diethylene Glycol Dibutyl Ether (DGDE) at both ambient (298 K) and elevated (398 K) temperatures from 1 to 168 hours. Mass changes of NBR before and after ageing indicated that NBR had distinct ageing dynamics in different model base oils and at different temperatures. For NBR aged in nonpolar HEX, the rate of weight loss of the rubber was larger at 398 K compared to that at 298 K. On the contrary, distinct weight-gaining (swelling) dynamics were observed for NBR aged in polar DGDE at 298 and 398 K. Based on Fourier Transform Infrared (FTIR), liquid and solid-state Nuclear Magnetic Resonance (NMR) spectroscopy and Energy Dispersive Spectroscopy (EDS) analysis it was found that aldehydes and sulfur- and zinc-containing compounds were leached out from NBR aged in both HEX and DGDE. The results of tribological studies showed that the non-aged NBR has a good wear-resistance. NBR samples had a very similar surface topography before and after tribo-tests. However, the worn surfaces of NBR samples were characterized by fine scoring (abrasion) marks after ageing in both model base oils. This has been attributed to changes in the steel-rubber contact environment during the sliding process and degradation of mechanical properties of NBR after ageing. For one NBR sample (after ageing in HEX at 398 K) very stable friction in the steel-rubber contact was observed.

  • 231.
    Wang, Zhou
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Temperature-dependent changes of physicochemical and tribological properties of acrylonitrile-butadiene rubber elastomer upon ageing in hexadecane and diethylene glycol dibutyl ether2013In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 227, no 8, p. 826-836Article in journal (Refereed)
    Abstract [en]

    Acrylonitrile-butadiene rubber elastomers are widely used in seal and tire industries. Physiochemical, surface and tribological properties of acrylonitrile-butadiene rubber exposed to a lubricant in a sealed mechanical contact may gradually change, in particular, at elevated temperatures. In this study, industrial-grade acrylonitrile-butadiene rubber elastomers were aged in two model non-additivated base oils, namely non-polar hexadecane and polar diethylene glycol dibutyl ether at both ambient (298 K) and elevated (398 K) temperatures from 1 to 168 h. Mass changes of acrylonitrile-butadiene rubber before and after ageing indicated that acrylonitrile-butadiene rubber had distinct ageing dynamics in different model base oils and at different temperatures. For acrylonitrile-butadiene rubber aged in nonpolar hexadecane, the rate of weight loss of the rubber was larger at 398 K compared to that at 298 K. On the contrary, distinct weight-gaining (swelling) dynamics were observed for acrylonitrile-butadiene rubber aged in polar diethylene glycol dibutyl ether at 298 and 398 K. Based on Fourier transform infrared spectroscopy, liquid and solid-state nuclear magnetic resonance spectroscopy and energy dispersive spectroscopy analyses, it was found that aldehydes and sulfur- and zinc-containing compounds were leached out from acrylonitrile-butadiene rubber aged in both hexadecane and diethylene glycol dibutyl ether. The results of tribological studies showed that the non-aged acrylonitrile-butadiene rubber has a good wear-resistance. Acrylonitrile-butadiene rubber samples had a very similar surface topography before and after tribo-tests. However, the worn surfaces of acrylonitrile-butadiene rubber samples were characterized by fine scoring (abrasion) marks after ageing in both model base oils. This has been attributed to changes in the steel–rubber contact environment during the sliding process and degradation of mechanical properties of acrylonitrile-butadiene rubber after ageing. For one acrylonitrile-butadiene rubber sample (after ageing in hexadecane at 398 K), very stable friction in the steel–rubber contact was observed.

  • 232. Wani, M. F.
    et al.
    Mukerji, J.
    Central Glass and Ceramic Research Institute (CGCRI), Calcutta.
    Prakash, Braham
    Bandopadhyay, S.
    Central Glass and Ceramic Research Institute (CGCRI), Calcutta.
    Friction and wear behaviour of hot pressed SiAlON‑steel ball tribopair under reciprocating sliding conditions1993In: American Ceramic Society Bulletin, ISSN 0002-7812, E-ISSN 1945-2705, Vol. 7, no 9, p. 82-87Article in journal (Refereed)
    Abstract [en]

    Friction and wear characteristics of SiAlON (Si(6-x)Al(x)O(x)N(8-x) where x = 0.5, 1.0, and 2.0), pressure sintered with the composition shifted toward the oxygen corner, were studied using a steel ball bearing as the second member of a tribopair under reciprocating sliding conditions. Sliding distance, velocity, and load were the test variables.

  • 233.
    Wani, M. F.
    et al.
    Indian Institute of Technology, New Delhi.
    Prakash, Braham
    Das, P. K.
    Central Glass and Ceramic Research Institute (CGCRI), Calcutta.
    Reza, S. S.
    Indian Institute of Technology, New Delhi.
    Mukerji, J.
    Central Glass and Ceramic Research Institute (CGCRI), Calcutta.
    Friction and wear of HPSN bearing materials1997In: American Ceramic Society Bulletin, ISSN 0002-7812, E-ISSN 1945-2705, Vol. 76, no 8, p. 65-69Article in journal (Refereed)
    Abstract [en]

    Paper presents data on wear and friction of hot-pressed silicon nitride (HPSN) and its composites in contact with ball-bearing steel. The coefficient of friction under unlubricated sliding conditions was 0.45, and it did not change with load under lubricated conditions. The wear coefficient was the least for HPSN sintered with liquid in system containing yttria. HPSN containing 15 % of TiC showed the best wear resistance compared to HPSN with other concentrations of TiC or BN. No adhesive wear was detected.

  • 234.
    Yalamanchili, K.
    et al.
    Department of Physics, Chemistry and Biology (IFM), Linköping University.
    Jiménez-Piqué, E.
    Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica, Center for Research in Nanoengineering, CRnE-UPC Avda. Diagonal 647, 08028 Barcelona.
    Pelcastre, Leonardo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Bakoglidis, K.D.
    Department of Physics, Chemistry and Biology (IFM), Linköping University.
    Roa, J.J.
    Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica, Center for Research in Nanoengineering, CRnE-UPC Avda. Diagonal 647, 08028 Barcelona.
    Jöesaar, M.P Johansson
    Department of Physics, Chemistry and Biology (IFM), Linköping University.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Ghafoor, N.
    Department of Physics, Chemistry and Biology (IFM), Linköping University.
    Odén, M.
    Department of Physics, Chemistry and Biology (IFM), Linköping University.
    Influence of microstructure and mechanical properties on the tribological behavior of reactive arc deposited Zr-Si-N coatings at room and high temperature2016In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 304, p. 393-400Article in journal (Refereed)
    Abstract [en]

    Varying the Si-content in Zr-Si-N coatings from 0.2 to 6.3 at.% causes microstructural changes from columnar to nanocomposite structure and a hardness drop from 37 to 26 GPa. The softer nanocomposite also displays lower fracture resistance. The tribological response of these coatings is investigated under different contact conditions, both at room and elevated temperatures. At room temperature tribooxidation is found to be the dominant wear mechanism, where the nanocomposite coatings display the lowest wear rate of 0.64 × 10− 5 mm3/Nm, by forming an oxide diffusion barrier layer consisting of Zr, W, and Si. A transition in the dominant wear mechanism from tribooxidation to microploughing is observed upon increasing the test temperature and contact stress. Here, all coatings exhibit significantly higher coefficient of friction of 1.4 and the hardest coatings with columnar structure display the lowest wear rate of 10.5 × 10− 5 mm3/Nm. In a microscopic wear test under the influence of contact-induced dominant elastic stress field, the coatings display wedge formation and pileup due to accumulation of the dislocation-induced plastic deformation. In these tests, the nanocomposite coatings display the lowest wear rate of 0.56 × 10− 10 mm3/Nm, by constraining the dislocation motion.

  • 235.
    Yang, J.F.
    et al.
    Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Jiang, Y.
    Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei.
    Wang, X.P.
    Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei.
    Fang, Q.F.
    Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei.
    Effect of Si content on the microstructure and mechanical properties of Mo–Al–Si–N coatings2012In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 86, no 12, p. 2010-2013Article in journal (Refereed)
    Abstract [en]

    Mo-Al (Al/(Mo+Al)=6.5%)-Si-N coatings with silicon content ranging from 0 to 17at.% were fabricated using d.c. reactive unbalanced magnetron sputtering technique in an Ar-N2 mixture. Surface morphology, element and phase composition, residual stress and nanohardness of these coatings were studied by scanned electrical microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), residual stress tester, and nanoindenter, respectively.Results exhibit that the residual stress built in the coating are compressive in nature ranging between 0.6 and 1.8 GPa. Nanohardness of Mo-Al-Si-N coatings increased at first and then decreased with silicon content, reaching a maximum value of 36 GPa at 8.3 at.% Si. The optimum hardness could be ascribed to higher compressive stress and nanocomposite structure where nanocrystallite Mo-Al-Si-N embedded in amorphous Si3N4 matrix.

  • 236.
    Yang, J.F.
    et al.
    Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Yuan, Z.G.
    Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei.
    Jiang, Y.
    Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei.
    Wang, X.P.
    Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei.
    Fang, Q.F.
    Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei.
    Influence of sputtering target power on microstructure and mechanical properties of W-N and Ta-N coatings2012In: Nanoscience and Nanotechnology Letters, ISSN 1941-4900, E-ISSN 1941-4919, Vol. 4, no 6, p. 604-608Article in journal (Refereed)
    Abstract [en]

    W-N and Ta-N coatings were manufactured using r.f. reactive magnetron sputtering technique in mixed atmosphere of Ar+N 2. The effect of sputtering power on the microstructure and mechanical properties of these coatings has been investigated. It was found that increasing sputtering power induced structure transformation of W-N and Ta-N coatings from hexagonal WN to fcc ω-W2N and from fcc TaN through a mixture of orthorhombic Ta3N5 and fcc TaN to orthorhombic Ta3N5, respectively. The increase in sputtering power led to grain refinement which played a major role in hardness enhancement. At the highest sputtering power of 100W, the average grain size of Ta-N and W-N coatings reduced to minimum value of 7 nm and 21 nm, correspondingly the hardness reached maximum value of 29 GPa and 31 GPa, respectively. However, Ta-N and W-N coatings possessed the biggest adhesion strength of ̃41 N and ̃48 N at the lowest sputtering power of 40 W and 25 W, respectively.

  • 237.
    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 University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    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 review2013In: Frontiers of Materials Science, ISSN 2095-025X, E-ISSN 2095-0268, Vol. 7, no 1, p. 28-39Article in journal (Refereed)
    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.

  • 238.
    Yazawa, Shuichiro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Minami, Ichiro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Reducing Friction and Wear of Tribological Systems through Hybrid Tribofilm Consisting of Coating and Lubricants2014In: Lubricants, ISSN 2075-4442, Vol. 2, p. 90-112Article in journal (Refereed)
    Abstract [en]

    The role of surface protective additives becomes vital when operating conditionsbecome severe and moving components operate in a boundary lubrication regime. Afterprotecting film is slowly removed by rubbing, it can regenerate through the tribochemicalreaction of the additives at the contact. However, there are limitations about theregeneration of the protecting film when additives are totally consumed. On the other hand,there are a lot of hard coatings to protect the steel surface from wear. These can enable thefunctioning of tribological systems, even in adverse lubrication conditions. However, hardcoatings usually make the friction coefficient higher, because of their high interfacial shearstrength. Amongst hard coatings, diamond-like carbon (DLC) is widely used, because of itsrelatively low friction and superior wear resistance. In practice, conventional lubricantsthat are essentially formulated for a steel/steel surface are still used for lubricating machinecomponent surfaces provided with protective coatings, such as DLCs, despite the fact thatthe surface properties of coatings are quite different from those of steel. It is thereforeimportant that the design of additive molecules and their interaction with coatingsshould be re-considered. The main aim of this paper is to discuss the DLC and theadditive combination that enable tribofilm formation and effective lubrication oftribological systems.

  • 239.
    Yonehara, M.
    et al.
    Tokyo University of Science.
    Okubo, H.
    Tokyo University of Science, Japan.
    Tadokoro, C.
    Saitama University, Japan.
    Sasaki, S.
    Tokyo University of Science, Japan.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Proposal of Biomimetic Tribological System to Control Friction Behavior under Boundary Lubrication by Applying 3D Metal Printing Process2018In: Tribology Online, ISSN 1881-218X, Vol. 13, no 1, p. 8-14Article in journal (Refereed)
    Abstract [en]

    A new concept was proposed as biomimetic tribological (BMT) system by using three-dimensional (3D) printing process. The BMT had a lubricant supply path (LSP) beneath the sliding surface. The tribological properties could be actively controlled by directly supplying lubricant additives (anti-wear additive and friction modifier) alone to the sliding surface through the LSP during a friction process. To confirm the effectiveness of the LSP surface for improving the tribological performance under boundary lubrication, friction tests were conducted on a plate specimen with a lubricant supply path that was manufactured by a 3D metal printer. Experimental results suggest that the LSP surface system was more effective for friction reduction than a conventional system, and it offered an effective way to actively control the tribological performance under boundary lubrication. 

  • 240.
    Ytrehus, Jan David
    et al.
    Sintef Petroleum AS.
    Taghipour, Ali
    Sintef Petroleum AS.
    Golchin, Arash
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Saasen, Arild
    Det Norske oljeselskap.
    The effect of different oil based drilling fluids on mechanical friction2015In: Proceedings of the ASME 34th International Conference on Ocean, Offshore and Arctic Engineering - 2015: presented at ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering; May 31 - June 5, 2015, St. John's, Newfoundland, Canada, New York: American Society of Mechanical Engineers , 2015, Vol. 10 : Petroleum technology, article id OMAE2015-41896Conference paper (Refereed)
    Abstract [en]

    A very important aspect in highly inclined wellbores is the mechanical friction. For extended reach drilling (ERD) and through tubing extended reach drilling (TTERD) this can be a limiting factor. Friction caused by the contact between the drill string and the well casing or borehole is dependent to the drilling weight and fluid properties. Drilling fluids play an important role on mechanical friction and using oil based drilling fluids with higher lubricity can reduce torque and drag behavior and minimize stick and slip. Reducing mechanical friction will improve drilling efficiency in general, and will in particular enable longer reach for ERD wells.This paper presents results from experimental laboratory tests where mechanical friction has been investigated. The experiments have been conducted as part of a project in the Tribolab at Luleå University of Technology in cooperation with Det norske Oljeselskap.Friction behavior has been investigated for different drilling fluids; water based and oil based drilling fluids both with and without solid particles. A pin on disc setup was used for these experiments where a spherical steel pin was sliding on a rotational disc made of granite. Friction force has been measured in constant sliding speed and in presence of particles in wet condition. The test results show that mechanical friction in general is smaller with oil based than water based drilling fluids in the presence of solid particles. In addition, the friction coefficient increases when solid particles were added to the lubricants.Such experiments in a tribology laboratory are important to identify the effect of drilling fluids on mechanical friction from a basic point of view and isolated from all other wellbore parameters. It is interesting to monitor if the results from this setup can have quantitative relevance also for field situations and such comparison should be done as follow up. Test results and the experimental approach could therefore be of value for any one working with drilling and well construction.

  • 241.
    Ytrehus, Jan David
    et al.
    Sintef Petroleum AS.
    Taghipour, Ali
    Sintef Petroleum AS.
    Golchin, Arash
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Saasen, Arild
    Department of Petroleum Engineering, University of Stavanger.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    The Effect of Different Drilling Fluids on Mechanical Friction2017In: Journal of energy resources technology, ISSN 0195-0738, E-ISSN 1528-8994, Vol. 139, no 3, article id 034502Article in journal (Refereed)
    Abstract [en]

    A very important aspect in highly inclined wellbores is the mechanical friction. For extended reach drilling (ERD) and through tubing extended reach drilling (TTERD) this can be a limiting factor. Friction caused by the contact between the drill string and the well casing or borehole is dependent on the drilling weight and fluid properties. Drilling fluids play an important role in determining mechanical friction. The use of oil-based drilling fluids with higher lubricity can reduce torque and drag behavior and minimize stick and slip. Reducing mechanical friction will improve drilling efficiency in general, and will in particular enable longer reach for ERD wells. This paper presents results from experimental laboratory tests where the mechanical friction has been investigated. Friction behavior was investigated for different drilling fluids; water-based and oil-based drilling fluids both with and without solid particles. A pin on disk setup was used for these experiments where a spherical ended steel pin was slid against a rotating disk made of granite. The test results show that the mechanical friction in general is smaller with oil-based than water-based drilling fluids in the presence of solid particles.

  • 242.
    Zhang, Chen Hui
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Zhao, Ying Chun
    State Key Laboratory of Tribology, Tsinghua University, Beijing.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Wang, Yan
    State Key Laboratory of Tribology, Tsinghua University, Beijing.
    Lou, Jian Bin
    State Key Laboratory of Tribology, Tsinghua University, Beijing.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    EHL properties of polyalkylene glycols and their aqueous solutions2012In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 45, no 3, p. 379-385Article in journal (Refereed)
    Abstract [en]

    Polyalkylene glycols (PAGs) are a type of synthetic lubricants widely used as compressor lubricants, gear oils, hydraulic fluids, and metal working fluids. The PAGs with typical molecular structure can dissolve in water, which makes it a candidate for the base stock of water-based lubricants. Till now, most of the investigations on the water-based lubrication have focussed on the additives. In this work, the potential of PAGs aqueous solutions to replace water as base stocks has been investigated. Four types of PAGs with different molecular weight and their aqueous solutions with different concentrations were studied to reveal their elastohydrodynamic lubrication (EHL) behavior. It has been found that the PAGs solutions can form EHL film like traditional oils. The film-forming capability depends on the viscosity, the pressure-viscosity coefficient, and the molecular weight of PAGs. The results indicate that the PAGs aqueous solution can be employed as base stocks of water-based lubricant

  • 243.
    Zhang, Chenhui
    et al.
    State Key Laboratory of Tribology, Tsinghua University, Beijing.
    Zhao, Yingchun
    State Key Laboratory of Tribology, Tsinghua University, Beijing.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Luo, Jianbin
    State Key Laboratory of Tribology, Tsinghua University, Beijing.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Film forming characteristics of polyalkylene glycols aqueous solutions in EHL contact2011In: 6th China International Symposium on Tribology: August 19-22, 2011, Lanzhou, China, Lanzhou, China: State Key Laboratory of Solid Lubrication , 2011, p. 121-121Conference paper (Refereed)
  • 244.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Högmark, Sture
    Ångström Laboratory, Uppsala University.
    Selected papers from those presented at the 14th Nordic Symposium on Tribology (Nordtrib 2010) Storforsen, June 8-11, 20102011In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 273, no 1, p. 1-Article in journal (Other academic)
2345 201 - 244 of 244
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