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Gebretsadik, D., Hardell, J. & Prakash, B. (2020). Friction and wear characteristics of PA 66 polymer composite/316L stainless steel tribopair in aqueous solution with different salt levels. Tribology International, 141, Article ID 105917.
Open this publication in new window or tab >>Friction and wear characteristics of PA 66 polymer composite/316L stainless steel tribopair in aqueous solution with different salt levels
2020 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 141, article id 105917Article in journal (Refereed) Published
Abstract [en]

Friction and wear behaviour of a PA 66 composite with 25% glass fibre reinforcement sliding against a 316L stainless steel have been investigated using different aqueous solutions under mixed/boundary lubrication. The aqueous solutions used are deionized water, seawater, seawater without group II metal salts, solution of dissolved Group II metal salts and solution of group II metal salts and NaHCO3. Lower friction and wear was obtained when lubricated with seawater. However, when deionized water or salt solutions without group II metal salts is used, increased wear was observed. The lower friction and wear in seawater solution is due to group II metal ions and bicarbonate ions that facilitate formation of the sparingly soluble carbonates that act as a lubricating tribofilm.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Polyamide, Glass fibre, Seawater, Wear
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements; Machine Elements
Identifiers
urn:nbn:se:ltu:diva-75823 (URN)10.1016/j.triboint.2019.105917 (DOI)2-s2.0-85071643762 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-09-10 (johcin)

Available from: 2019-09-03 Created: 2019-09-03 Last updated: 2019-09-20Bibliographically approved
Hultqvist, T., Vrček, A., Marklund, P., Prakash, B. & Larsson, R. (2020). Transient analysis of surface roughness features in thermal elastohydrodynamic contacts. Tribology International, 141, Article ID 105915.
Open this publication in new window or tab >>Transient analysis of surface roughness features in thermal elastohydrodynamic contacts
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2020 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 141, article id 105915Article in journal (Refereed) Published
Abstract [en]

Understanding the influence of surface roughness in elastohydrodynamically lubricated (EHL) contacts is essential to improve durability and friction performance of machine elements employing non-conformal contacting surfaces. In this work, the transient event of a surface feature passing through a thermal EHL line contact operating under different sliding conditions is investigated with the purpose of providing a deeper understanding of surface roughness influence. This is achieved by solving the EHL problem in space and time. It was seen that sliding influences the temperature rise in the contact significantly, especially in the vicinity of the asperity. However, due to the characteristic behaviour of EHL contacts, the local temperature rise mainly influence the film thickness during exiting of inlet perturbations and the asperity.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Thermal elastohydrodynamic lubrication, Transient conditions, Surface features, Numerical modelling
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-75817 (URN)10.1016/j.triboint.2019.105915 (DOI)2-s2.0-85071778495 (Scopus ID)
Funder
Swedish Energy Agency, 41215-1
Note

Validerad;2019;Nivå 2;2019-09-10 (johcin)

Available from: 2019-09-03 Created: 2019-09-03 Last updated: 2019-09-20Bibliographically approved
Gebretsadik, D., Hardell, J. & Prakash, B. (2019). Embeddability behaviour of some Pb-free engine bearing materials in the presence of abrasive particles in engine oil. Tribology - Materials, Surfaces & Interfaces, 13(1), 39-49
Open this publication in new window or tab >>Embeddability behaviour of some Pb-free engine bearing materials in the presence of abrasive particles in engine oil
2019 (English)In: Tribology - Materials, Surfaces & Interfaces, ISSN 1751-5831, E-ISSN 1751-584X, Vol. 13, no 1, p. 39-49Article in journal (Refereed) Published
Abstract [en]

One of the tribological requirements on engine bearing material is its ability to safely embed contaminant particles onto its surface and minimise damage to both the bearing and crankshaft surfaces. In this work, a journal bearing test rig that operates under constant load has been employed to investigate the embeddability behaviour of selected multi-layered Pb-free engine bearing materials at three different rotational speeds using engine oil contaminated with SiC particles. Experimental results have shown that third-body abrasive wear is influenced by the lubricant film thickness. There was also difference in embeddability of the different materials. Bismuth-based overlay and MoS2 containing polyamide-imide-based overlay-coated materials show higher wear compared to tin-based overlay and a polyamide-imide-based composite overlay-coated material. Steel counter surfaces sliding against bismuth-based overlay and MoS2 containing polyamide-imide-based overlay exhibited higher wear than those sliding against tin-based overlay and polyamide-imide-based composite overlay. 

Place, publisher, year, edition, pages
Taylor & Francis, 2019
Keywords
Embeddability, third-body abrasive wear, hydrodynamic lubrication, engine bearings, Pb-free
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-72774 (URN)10.1080/17515831.2019.1574452 (DOI)000471166200005 ()
Note

Validerad;2019;Nivå 2;2019-04-12 (oliekm)

Available from: 2019-02-04 Created: 2019-02-04 Last updated: 2019-07-01Bibliographically approved
Mozgovoy, S., Hardell, J. & Prakash, B. (2019). High Temperature Friction and Wear Performance of PVD Coatings under Press Hardening Contact Conditions. Advances in Tribology, 2019, Article ID 4981246.
Open this publication in new window or tab >>High Temperature Friction and Wear Performance of PVD Coatings under Press Hardening Contact Conditions
2019 (English)In: Advances in Tribology, ISSN 1687-5915, E-ISSN 1687-5923, Vol. 2019, article id 4981246Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Hindawi Publishing Corporation, 2019
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-73812 (URN)10.1155/2019/4981246 (DOI)000466291800001 ()2-s2.0-85065224213 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-05-02 (johcin)

Available from: 2019-05-02 Created: 2019-05-02 Last updated: 2019-06-25Bibliographically approved
Johansson, J., Devlin, M. T., Guevremont, J. M. & Prakash, B. (2019). Improving Hypoid Gear Oil Pitting Performance through Friction Reduction. Tribology Transactions
Open this publication in new window or tab >>Improving Hypoid Gear Oil Pitting Performance through Friction Reduction
2019 (English)In: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397XArticle in journal (Refereed) Epub ahead of print
Abstract [en]

Earlier studies have shown that the load-dependent friction behavior of various gear oils can affect their pitting performance; that is, low friction resulted in a long pitting life. These studies were limited, however, to test methods and running conditions quite different from those occurring in actual gear transmissions. In the present study, a more gear-like twin-disc machine with test specimens and running conditions relevant for gear contacts was used to investigate whether the same trends could be found. To analyze this possible correlation, the first step was to prepare a set of hypoid gear oils and to test their friction performance to compare various ways of improving friction behavior but also to form an understanding of why their friction performance varied. The second step was to test the pitting performance of the oils. The pitting results could then be compared to the friction properties of the oils to analyze the correlation. Other possible mechanisms behind the formation of pits are also discussed. The results show that for the oils included, the antiwear and extreme-pressure additive package and the base oil type affect friction. The results further show that additive combinations and/or base oils that result in low friction lead to enhanced pitting performance.

Place, publisher, year, edition, pages
Taylor & Francis, 2019
Keywords
Gear lubricants, rolling contact fatigue, EHL friction, antifatigue additives
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-76575 (URN)10.1080/10402004.2019.1686194 (DOI)000497233100001 ()2-s2.0-85075217917 (Scopus ID)
Available from: 2019-10-30 Created: 2019-10-30 Last updated: 2019-12-10
Hultqvist, T., Vrček, A., Prakash, B., Marklund, P. & Larsson, R. (2019). Influence of lubricant pressure response on sub-surface stress in elastohydrodynamically lubricated finite line contacts. Journal of tribology, 141(3), Article ID 031502.
Open this publication in new window or tab >>Influence of lubricant pressure response on sub-surface stress in elastohydrodynamically lubricated finite line contacts
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2019 (English)In: Journal of tribology, ISSN 0742-4787, E-ISSN 1528-8897, Vol. 141, no 3, article id 031502Article in journal (Refereed) Published
Abstract [en]

In order to adapt to increasingly stringent CO2 regulations, the automotive industry must develop and evaluate low cost, low emission solutions in the powertrain technology. This often implies increased power density and the use of low viscosity oils, leading to additional challenges related to the durability of various machine elements. Therefore, an increased understanding of lubricated contacts becomes important where oil viscosity-pressure and compressibility-pressure behaviour have been shown to influence the film thickness and pressure distribution in EHL contacts, further influencing the durability. In this work, a finite line EHL contact is analysed with focus on the oil compressibility- and viscositypressure response, comparing two oils with relatively different behaviour and its influence on subsurface stress concentrations in the contacting bodies. Results indicate that increased pressure gradients and pressure spikes, and therefore increased localized stress concentrations, can be expected for stiffer, less compressible oils, which under transient loading conditions not only affect the outlet but also the edges of the roller

Place, publisher, year, edition, pages
ASME Press, 2019
Keywords
Elastohydrodynamic lubrication, Finite line contacts, Sub-surface stress, Transient loading
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-71551 (URN)10.1115/1.4041733 (DOI)000457029800007 ()2-s2.0-85057759100 (Scopus ID)
Funder
Swedish Energy Agency, 41215-1
Note

Validerad;2018;Nivå 2;2018-12-07 (johcin)

Available from: 2018-11-12 Created: 2018-11-12 Last updated: 2019-09-13Bibliographically approved
Mozgovoy, S., Alik, L., Hardell, J. & Prakash, B. (2019). Material transfer during high temperature sliding of Al-Si coated 22MnB5 steel against PVD coatings with and without aluminium. In: Wear of Materials: . Paper presented at 22nd International Conference on Wear of Materials, April 14-18 2019, Miami, USA (pp. 401-411). Elsevier, 426-427
Open this publication in new window or tab >>Material transfer during high temperature sliding of Al-Si coated 22MnB5 steel against PVD coatings with and without aluminium
2019 (English)In: Wear of Materials, Elsevier, 2019, Vol. 426-427, p. 401-411Conference paper, Published paper (Refereed)
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.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Friction, Wear, High temperature, PVD coating, Aluminium
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-73686 (URN)10.1016/j.wear.2018.12.042 (DOI)000464583700043 ()
Conference
22nd International Conference on Wear of Materials, April 14-18 2019, Miami, USA
Available from: 2019-04-17 Created: 2019-04-17 Last updated: 2019-04-30Bibliographically approved
Deng, L., Pelcastre, L., Hardell, J., Prakash, B. & Oldenburg, M. (2019). Numerical investigation of galling in a press hardening experiment with AlSi-coated workpieces. Engineering Failure Analysis, 99, 85-96
Open this publication in new window or tab >>Numerical investigation of galling in a press hardening experiment with AlSi-coated workpieces
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2019 (English)In: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 99, p. 85-96Article in journal (Refereed) Published
Abstract [en]

Press hardened steels are commonly used as a lightweight choice for manufacturing car components because of the high ratio of strength to weight. The use of ultra-high-strength steels for the design of lightweight vehicles contributes to the reduction of emissions of carbon dioxide while maintaining passenger safety. Stamping tools used in press hardening processes suffer harsh contact conditionsin terms of dramatic temperature changes, cyclic loadings, and complex interactions between coatings and oxidation. In mass production, tool wear is an inevitable problem that increases maintenance costs. Severe adhesive wear, also called galling, substantially occurs in the stamping tool used against Al—Si-coated workpieces. The galling that takes place during press hardening not only degrades the production quality but also shortens the service life of the tool. In order to properly arrange tool maintenance and minimize galling through adjusting process parameters, engineers need to know when and where galling occurs, based on modelling of the galling in press hardening simulations. In order to implement a galling simulation for press hardening, a modified Archard wear model is employed in the present study, which is a contact-mechanics-based model. The specific wear rate in the model is calibrated by the quantitative galling measurements of a high-temperature tribometer test. The tribological test is designed to mimic the press hardening conditions, where the correlations between galling and process parameters such as temperature, pressure, and sliding distance are outlined. The galling simulation is implemented in a full-scale press hardening experiment, and the predicted galling is validated in terms of severe galling positions and galling profiles. The galling profile evolution is correlated to variations in the contact conditions. Uncertainties in the numerical model, such as the choice of penalty scaling factor and friction coefficient, are analysed with a parameter study and discussed. This study demonstrates finite element (FE) simulations involving galling prediction in press hardening so as to improve product development and production efficiency.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Contact conditions, High-temperature tribometer, FE simulation, Galling prediction
National Category
Applied Mechanics Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Solid Mechanics; Machine Elements
Identifiers
urn:nbn:se:ltu:diva-73044 (URN)10.1016/j.engfailanal.2019.01.059 (DOI)000464957800008 ()2-s2.0-85061604416 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-02-27 (johcin)

Available from: 2019-02-27 Created: 2019-02-27 Last updated: 2019-05-02Bibliographically approved
Torres, H., Rodriguez Ripoll, M. & Prakash, B. (2019). Self-lubricating laser claddings for friction control during press hardening of Al-Si-coated boron steel. Journal of Materials Processing Technology, 269, 79-90
Open this publication in new window or tab >>Self-lubricating laser claddings for friction control during press hardening of Al-Si-coated boron steel
2019 (English)In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 269, p. 79-90Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
High Temperature, Laser Cladding, Self-Lubrication, Adhesion Wear, Hot Stamping
National Category
Manufacturing, Surface and Joining Technology Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-71708 (URN)10.1016/j.jmatprotec.2019.02.002 (DOI)000464299300009 ()2-s2.0-85061155760 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-02-18 (svasva)

Available from: 2018-11-22 Created: 2018-11-22 Last updated: 2019-04-29Bibliographically approved
Mishra, T., Nordin, B., Svanbäck, D., Tervakangas, S. & Prakash, B. (2019). The effects of contact configuration and coating morphology on the tribological behaviour of tetrahedral amorphous diamond-like carbon (ta-C DLC) coatings under boundary lubrication. Tribology - Materials, Surfaces & Interfaces, 13(2), 120-129
Open this publication in new window or tab >>The effects of contact configuration and coating morphology on the tribological behaviour of tetrahedral amorphous diamond-like carbon (ta-C DLC) coatings under boundary lubrication
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2019 (English)In: Tribology - Materials, Surfaces & Interfaces, ISSN 1751-5831, E-ISSN 1751-584X, Vol. 13, no 2, p. 120-129Article in journal (Refereed) Published
Abstract [en]

Tribological studies were carried out with tetrahedral amorphous diamond-like carbon (ta-C DLC) coatings, varying in thickness and roughness, using two different contact configurations lubricated with seven types of hydraulic oils. Tribopair of cast iron and ta-C coated steel were tested in both non-conformal and conformal, unidirectional sliding contacts. The friction and wear results were mainly affected by the thickness of the coating in the non-conformal contact and the surface roughness of the coating in the conformal contact. Tests done with mineral base oil containing rust inhibitor in the non-conformal contact and with Polyalphaolefins and synthetic ester base oils in the conformal contact resulted in the lowest friction while that with mineral base oil containing zinc resulted in high friction and counterface wear. The results highlight the interdependence of contact configuration, lubricant chemistry, coating’s surface morphology and coating’s thickness in determining the tribological behaviour of ta-C coatings under boundary lubrication.

Place, publisher, year, edition, pages
Taylor & Francis, 2019
Keywords
Diamond-like carbon (DLC) coating, tetrahedral amorphous carbon (ta-C) coating, boundary lubrication, ultralow friction, contact configuration, pin-on-disc test, block-on-ring test, DLC coating-iron contact
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-73429 (URN)10.1080/17515831.2019.1596627 (DOI)000470002500006 ()
Note

Validerad;2019;Nivå 2;2019-04-11 (johcin)

Available from: 2019-04-04 Created: 2019-04-04 Last updated: 2019-06-24Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-1454-1118

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