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Publications (10 of 15) Show all publications
Ghasemi, R., Johansson, J., Ståhl, J.-E. & Jarfors, A. E. .. (2019). Load effect on scratch micro-mechanisms of solution strengthened Compacted Graphite Irons. Tribology International, 133, 182-192
Open this publication in new window or tab >>Load effect on scratch micro-mechanisms of solution strengthened Compacted Graphite Irons
2019 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 133, p. 182-192Article in journal (Refereed) Published
Abstract [en]

This study investigates the scratch load effect, from 100 to 2000 mN, on micro-mechanisms involved during scratching. A pearlitic and three ferritic Compacted Graphite Irons (CGI) solution strengthened through addition of 3.66, 4.09, and 4.59 Si wt% were investigated. Good correlation was observed between hardness measurements, tensile testing, and scratch results explaining the influence of matrix characteristics on scratch behaviour for investigated alloys. A significant matrix deformation, change in frictional force and scratch coefficient of friction was observed by increase in scratch load. In all cases, microscratch depth and width increased significantly with load increasing, however pearlitic CGI showed most profound deformation, while the maximum and minimum scratch resistances were observed for high-Si ferritic and pearlitic CGI alloys, respectively.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
CGI, Si solution-strengthening, Scratch testing, Deformation micro-mechanisms during scratching
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-42653 (URN)10.1016/j.triboint.2019.01.010 (DOI)000458943500018 ()2-s2.0-85059818887 (Scopus ID)PP JTH 2019 embargo 24 (Local ID)PP JTH 2019 embargo 24 (Archive number)PP JTH 2019 embargo 24 (OAI)
Available from: 2019-01-16 Created: 2019-01-16 Last updated: 2019-03-13Bibliographically approved
Ghasemi, R., Elmquist, L., Ghassemali, E., Salomonsson, K. & Jarfors, A. E. .. (2018). Abrasion resistance of lamellar graphite iron: Interaction between microstructure and abrasive particles. Tribology International, 120, 465-475
Open this publication in new window or tab >>Abrasion resistance of lamellar graphite iron: Interaction between microstructure and abrasive particles
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2018 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 120, p. 465-475Article in journal (Refereed) Published
Abstract [en]

This study focuses on abrasion resistance of Lamellar Graphite Iron (LGI) using microscratch test under constant and progressive load conditions. The interactions between a semi-spherical abrasive particle, cast iron matrix and graphite lamellas were physically simulated using a sphero-conical indenter. The produced scratches were analysed using LOM and SEM to scrutinise the effect of normal load on resulting scratch depth, width, frictional force, friction coefficient and deformation mechanism of matrix during scratching. Results showed a significant matrix deformation, and change both in frictional force and friction coefficient by increase of scratch load. Furthermore, it was shown how abrasive particles might produce deep scratches with severe matrix deformation which could result in graphite lamella's coverage and thereby deteriorate LGI's abrasion resistance.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Lamellar graphite cast iron; Abrasion resistance; Scratch test; Microstructure; Pearlite deformation
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-38473 (URN)10.1016/j.triboint.2017.12.046 (DOI)000428102900046 ()2-s2.0-85041480396 (Scopus ID)
Available from: 2018-01-12 Created: 2018-01-12 Last updated: 2019-02-15Bibliographically approved
Malakizadi, A., Ghasemi, R., Behring, C., Olofsson, J., Jarfors, A. E. .., Nyborg, L. & Krajnik, P. (2018). Effects of workpiece microstructure, mechanical properties and machining conditions on tool wear when milling compacted graphite iron. Wear, 410-411, 190-201
Open this publication in new window or tab >>Effects of workpiece microstructure, mechanical properties and machining conditions on tool wear when milling compacted graphite iron
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2018 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 410-411, p. 190-201Article in journal (Refereed) Published
Abstract [en]

The aim of the present study was to investigate the tool performance when machining compacted graphite iron (CGI) alloys. A comparison was made between solid solution strengthened CGI including various amounts of silicon (Si-CGI) and the pearlitic-ferritic CGI as a reference material. The emphasis was on examining the influence of microstructure and mechanical properties of the material on tool wear in face milling process. Machining experiments were performed on the engine-like test pieces comprised of solid solution strengthened CGI with three different silicon contents and the reference CGI alloy. The results showed up-to 50% lower flank wear when machining Si-CGI alloys, although with comparable hardness and tensile properties. In-depth analysis of the worn tool surfaces showed that the abrasion and adhesion were the dominant wear mechanisms for all investigated alloys. However, the better tool performance when machining Si-CGI alloys was mainly due to a lower amount of abrasive carbo-nitride particles and the suppression of pearlite formation in the investigated solid solution strengthened alloys.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Casting, CGI, Machinability, Milling, Solution hardening, Tool wear, Graphite, Iron alloys, Mechanical properties, Microstructure, Milling (machining), Pearlite, Silicon alloys, Solid solutions, Wear of materials, Compacted graphite iron, Machining conditions, Machining experiments, Microstructure and mechanical properties, Pearlite formations, Reference material, Cutting tools
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-41217 (URN)10.1016/j.wear.2018.07.005 (DOI)000440030600019 ()2-s2.0-85050005596 (Scopus ID)
Funder
VINNOVA, GNR 2012_137 2.4.2Knowledge Foundation, GNR 20100218
Available from: 2018-08-23 Created: 2018-08-23 Last updated: 2019-02-14Bibliographically approved
Ghasemi, R. & Jarfors, A. E. .. (2018). Scratch behaviour of silicon solid solution strengthened ferritic compacted graphite iron (CGI). Paper presented at 11th International Symposium on the Science and Processing of Cast Iron, SPCI-XI 2017, Jönköping, Sweden, 4-7 September 2017. Materials Science Forum, 318-325
Open this publication in new window or tab >>Scratch behaviour of silicon solid solution strengthened ferritic compacted graphite iron (CGI)
2018 (English)In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, p. 318-325Article in journal (Refereed) Published
Abstract [en]

The present study focuses on scratch behaviour of a conventional pearlitic and a number of solid solution strengthened ferritic Compacted Graphite Iron (CGI) alloys. This was done by employing a single-pass microscratch test using a sphero-conical diamond indenter under different constant normal load conditions. Matrix solution hardening was made by alloying with different contents of Si; (3.66, 4.09 and 4.59 wt%. Si) which are named as low-Si, medium-Si and high-Si ferritic CGI alloys, respectively. A good correlation between the tensile and scratch test results was observed explaining the influence of CGI’s matrix characteristics on scratch behaviour both for pearlitic and fully ferritic solution strengthened ones. Both the scratch depth and scratch width showed strong tendency to increase with increasing the normal load, however the pearlitic one showed more profound deformation compared to the solution strengthened CGI alloys. Among the investigated alloys, the maximum and minimum scratch resistance were observed for high-Si ferritic CGI and pearlitic alloys, respectively. It was confirmed by the scratched surfaces analysed using Scanning Electron Microscopy (SEM) as well. In addition, the indenter’s depth of penetration value (scratch depth) was found as a suitable measure to ascertain the scratch resistance of CGI alloys. 

Place, publisher, year, edition, pages
Trans Tech Publications, 2018
Keywords
Abrasion, CGI, Scratch resistance, Scratch testing, Silicon solution strengthening, Cast iron, Ferrite, Graphite, Pearlite, Scanning electron microscopy, Solid solutions, Compacted graphite iron, Diamond indenter, Good correlations, Micro-scratch test, Penetration values, Solution strengthening, Silicon alloys
National Category
Materials Engineering
Identifiers
urn:nbn:se:hj:diva-41279 (URN)10.4028/www.scientific.net/MSF.925.318 (DOI)XYZ ()2-s2.0-85050016378 (Scopus ID)9783035710557 (ISBN)
Conference
11th International Symposium on the Science and Processing of Cast Iron, SPCI-XI 2017, Jönköping, Sweden, 4-7 September 2017
Funder
Knowledge FoundationVINNOVA
Available from: 2018-08-28 Created: 2018-08-28 Last updated: 2019-01-25Bibliographically approved
Ghasemi, R., Olofsson, J., Jarfors, A. E. W. & Svensson, I. L. (2017). Modelling and simulation of local mechanical properties of high silicon solution-strengthened ferritic compacted graphite iron. International Journal of Cast Metals Research, 30(3), 125-132
Open this publication in new window or tab >>Modelling and simulation of local mechanical properties of high silicon solution-strengthened ferritic compacted graphite iron
2017 (English)In: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 30, no 3, p. 125-132Article in journal (Refereed) Published
Abstract [en]

This study focuses on the modelling and simulation of local mechanical properties of compacted graphite iron cast at different section thicknesses and three different levels of silicon, ranging from about 3.6% up to 4.6%. The relationship between tensile properties and microstructure is investigated using microstructural analysis and statistical evaluation. Models are generated using response surface methodology, which reveal that silicon level and nodularity mainly affect tensile strength and 0.2% offset yield strength, while Young′s modulus is primarily affected by nodularity. Increase in Si content improves both the yield and tensile strength, while reduces elongation to failure. Furthermore, mechanical properties enhance substantially in thinner section due to the high nodularity. The obtained models have been implemented into a casting process simulation, which enables prediction of local mechanical properties of castings with complex geometries. Very good agreement is observed between the measured and predicted microstructures and mechanical properties, particularly for thinner sections.

Place, publisher, year, edition, pages
Taylor & Francis, 2017
Keywords
casting process simulation, Compacted graphite iron, materials characterisation, solution-strengthened ferrite, tensile properties, Cast iron, Casting, Ferrite, Ferritic steel, Graphite, Iron, Iron compounds, Mechanical properties, Microstructure, Silicon, Local mechanical properties, Microstructures and mechanical properties, Properties and microstructures, Response surface methodology, Yield and tensile strength, Tensile strength
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-34625 (URN)10.1080/13640461.2016.1261520 (DOI)000400800700001 ()2-s2.0-85006957496 (Scopus ID)
Funder
VINNOVA, DNR 2012_137 2.4.2
Available from: 2017-01-09 Created: 2017-01-09 Last updated: 2017-08-14
Ghasemi, R., Elmquist, L., Svensson, H., König, M. & Jarfors, A. E. W. (2016). Mechanical properties of solid solution-strengthened CGI. International Journal of Cast Metals Research, 29(1-2), 98-105
Open this publication in new window or tab >>Mechanical properties of solid solution-strengthened CGI
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2016 (English)In: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 29, no 1-2, p. 98-105Article in journal (Refereed) Published
Abstract [en]

Despite the increased usage of pearlitic compacted graphite iron (CGI) in heavy vehicle engines, poor machinability of this material remains as one of the main technical challenges as compared to conventional lamellar iron. To minimise the machining cost, it is believed that solution-strengthened CGI material with a ferritic matrix could bring an advantage. The present study focuses on the effect of solution strengthening of silicon and section thickness on tensile, microstructure and hardness properties of high-Si CGI materials. To do so, plates with thicknesses from 7 to 75 mm were cast with three different target silicon levels 3.7, 4.0 and 4.5 wt%. For all Si levels, the microstructure was ferritic with a very limited pearlite content. The highest nodularity was observed in 7 and 15 mm plate sections, respectively, however, it decreased as the plate thickness increased. Moreover, increasing Si content to 4.5 wt% resulted in substantial improvement up to 65 and 50% in proof stress and tensile strength, respectively, as compared to pearlitic CGI. However, adding up Si content to such a high level remarkably deteriorated elongation to failure. For each Si level, results showed that the Young’s modulus and tensile strength are fairly independent of the plate thickness (30–75 mm), however, a significant increase was observed for thin section plates, particularly 7 mm plate due to the higher nodularity in these sections.

Place, publisher, year, edition, pages
Taylor & Francis, 2016
Keywords
Compacted graphite iron, High-Si ferritic CGI, Mechanical properties, Solid solution strengthening, Ferrite
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-30841 (URN)10.1080/13640461.2015.1106781 (DOI)000377468800016 ()2-s2.0-84978389185 (Scopus ID)
Funder
VINNOVA
Note

Special Issue: Special Issue featuring papers from SPCI10

Available from: 2016-06-23 Created: 2016-06-23 Last updated: 2018-06-08Bibliographically approved
Ghasemi, R. (2016). The influence of microstructure on mechanical and tribological properties of lamellar and compacted irons in engine applications. (Doctoral dissertation). Jönköping: Jönköping University, School of Engineering
Open this publication in new window or tab >>The influence of microstructure on mechanical and tribological properties of lamellar and compacted irons in engine applications
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Lamellar graphite iron (LGI) is commonly used in diesel engine applications such as piston rings–cylinder liner where an excellent combination of physical and tribological properties is essential to avoid scuffing and bore polishing issues. The excellent tribological behaviour of LGI alloys is related to the graphite lamellas, which act as solid lubricant agents by feeding onto the tribosurfaces under sliding conditions. However, increasingly tighter emissions and fuel economy legislations and the higher demands on enhanced power and durability have encouraged both engine designers and manufacturers to introduce pearlitic compacted graphite irons (CGI) as an alternative material replacing LGI, although the poor machinability of pearlitic CGI alloys compared to the LGI remains a challenge.

The focus of this study is placed on investigating how the microstructure of LGI and CGI alloys affects their mechanical and tribological properties. This was initially undertaken by investigating representative, worn lamellar cast iron piston rings taken from a two-stroke large-bore heavy-duty diesel engine. As known that it is tribologically essential to keep the graphite open under sliding conditions, in particular under starved lubrication regimes or unlubricated conditions to avoid scuffing issues; however, this study revealed the closure of a majority of graphite lamellas; profoundly for those lamellas that were parallel to sliding direction; due to the severe matrix deformation caused by abrasion. Both microindentation and microscratch testing, which were used to crudely simulate the abrasion under starved lubricated condition in combustion chamber, suggested a novel mechanism of activating the graphite lamellas to serve as lubricating agents in which the matrix deformation adjacent to the graphite initially resulted in fracturing and then extrusion of the graphite lamellas.

Additionally, in order to investigate the relation between matrix constituents, mechanical properties and machinability of cast iron materials, solution-strengthened CGI alloys were produced with different levels of silicon and section thicknesses. The results showed significant improvements in mechanical properties and machinability while deteriorating the ductility. Moreover, multiple regression analysis, based on chemical composition and microstructural characteristics was used to model the local mechanical properties of high Si ferritic CGI alloys, followed by implementing the derived models into a casting process simulation which enables the local mechanical properties of castings with complex geometries. Very good agreement was observed between the measured and predicted microstructure and mechanical properties.

Place, publisher, year, edition, pages
Jönköping: Jönköping University, School of Engineering, 2016. p. 80
Series
JTH Dissertation Series ; 17
Keywords
Cast iron, Si solution-strengthened CGI, microstructure, mechanical properties, modelling and simulation, tribology, abrasive wear, scratch testing
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-32052 (URN)978-91-87289-18-7 (ISBN)
Public defence
2016-11-25, E1405, Jönköping University, School of Engineering, Jönköping, 10:00 (English)
Opponent
Supervisors
Available from: 2016-10-26 Created: 2016-10-26 Last updated: 2016-10-26Bibliographically approved
Ghasemi, R., Elmquist, L., Ghassemali, E. & Jarfors, A. E. W. (2015). Effect of interaction between lamellar graphite and cat-fines on tribological behaviour of cast iron under abrasion. In: Proceeding of ITC: . Paper presented at 6th International Tribology Conference, Tokyo, Japan, 16-20th September 2015.
Open this publication in new window or tab >>Effect of interaction between lamellar graphite and cat-fines on tribological behaviour of cast iron under abrasion
2015 (English)In: Proceeding of ITC, 2015Conference paper, Published paper (Refereed)
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-32049 (URN)
Conference
6th International Tribology Conference, Tokyo, Japan, 16-20th September 2015
Available from: 2016-10-26 Created: 2016-10-26 Last updated: 2016-10-26Bibliographically approved
Ghasemi, R. (2015). Tribological and Mechanical Behaviour of Lamellar and Compacted Graphite Irons in Engine Applications. (Licentiate dissertation). Jönköping: School of Engineering, Jönköping University Department of Materials and Manufacturing
Open this publication in new window or tab >>Tribological and Mechanical Behaviour of Lamellar and Compacted Graphite Irons in Engine Applications
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

There has been much discussion about the beneficial uses of lamellar graphite iron in piston rings–cylinder liner systems, where a good combinations of both thermal and tribological properties are essential. The excellent tribological performance of lamellar iron under such sliding conditions is principally associated with lubrication behaviour of the graphite particles which are distributed as lamellas throughout the matrix. During sliding, graphite particles are extruded and smeared onto the counterfaces, act as solid lubricating agents and form a thin graphite film between the sliding surfaces. Although this process especially, during the running-in period significantly changes the sliding wear response of the components, the exact mechanism behind of this phenomenon has rarely been discussed in previous studies.

It is tribologically beneficial to keep the graphite open, particularly in applications where the scuffing issues do matter. In this thesis, the main causes involved in closing the graphite lamellas are discussed, with a focus on matrix plastic deformation that occurs during sliding. In first step, the relationship between graphite lamellae orientation and plastic deformation was investigated. To do so, two piston rings, belonging to the same two-stroke marine engine operated for different periods of time, were selected and compared to the unworn sample. The worn piston rings displayed a substantial decrease in both frequency and area fraction of the graphite lamellas. Most of the lamellas were closed as a result of plastic deformation of matrix. This happening was caused mainly by the interaction between abrasive particles and metallic matrix. Additionally, it was found that graphite lamellas parallel or near-parallel to the sliding direction exhibited maximum closing tendency under sliding condition.

In next step, to have a better understanding of the graphite film formation mechanism and matrix deformation role in closing the graphite lamellas, microindentation and microscratch testing were performed on typical lamellar iron. The qualitative results showed a similar mechanism involving in graphite contribution to lubricate the sliding surfaces. Moreover, microindentations made nearby the graphite lamellas demonstrated that the deformation of the matrix causes the formation of cracks in the centre of the graphite lamellas, compressing and then extruding the graphite from its natural position, irrespective of the lamellas′ size. Furthermore, it was found that subsurface graphite orientation had a large influence on the extrusion behaviour, in that, for graphite lamellas oriented towards the indenter, the effect was observed more pronounced.

Furthermore, an improved fully ferritic solution strengthened compacted graphite iron was produced for future wear studies. The effects of different Si levels and section thicknesses on tensile properties and hardness were investigated as well. The influence of Si content and section thickness on mechanical properties was revealed by improving the materials strength and slightly enhancing the hardness through increasing Si content. Besides, Si addition up to 4.5 wt% significantly affected the strength and elongation to failure of cast samples.

Place, publisher, year, edition, pages
Jönköping: School of Engineering, Jönköping University Department of Materials and Manufacturing, 2015. p. 49
Series
JTH Dissertation Series ; 5
Keywords
Sliding wear, abrasive wear, graphite lubricating performance, matrix deformation, lamellar graphite iron, high-Si compacted graphite iron
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:hj:diva-25724 (URN)978-91-87289-06-4 (ISBN)
Presentation
2015-02-12, E1405, Gjuterigatan 5, Jönköping, Sweden, 12:24 (English)
Opponent
Supervisors
Projects
HeliosFFI
Funder
EU, European Research Council, 265861VINNOVA, DNR 2012_137 2.4.2
Available from: 2015-01-21 Created: 2015-01-21 Last updated: 2018-01-11Bibliographically approved
Ghasemi, R. & Elmquist, L. (2014). A study on graphite extrusion phenomenon under the sliding wear response of cast iron using microindentation and microscratch techniques. Wear, 320(1-2), 120-126
Open this publication in new window or tab >>A study on graphite extrusion phenomenon under the sliding wear response of cast iron using microindentation and microscratch techniques
2014 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 320, no 1-2, p. 120-126Article in journal (Refereed) Published
Abstract [en]

This study focuses on the graphite flakes extrusion mechanism during microindenting and microscratching of cast iron. Observations on the graphite response under abrasive conditions revealed that the matrix deformation which is occurred during a sliding wear condition could have a significant influence on its lubricating performance. Simple microindentation and microscratch tests were conducted to explore the lamellar graphite contribution to tribofilm formation under abrasive wear conditions. The results obtained showed that induced plastic deformation which developed adjacent to the graphite compressed the lamellas and in turn resulting in extrusion of the graphite from its natural position. Further investigations on both indentation and scratch tests indicated that, surprisingly, the graphite began to be fractured and extruded from the centre of graphite lamellas, irrespective of the lamella size. Additionally, a mechanism was proposed to explain the self-lubricating and the extrusion behaviour of the lamellar graphite as a result of indentation.

Place, publisher, year, edition, pages
Lausanne: Elsevier, 2014
Keywords
Lamellar graphite iron; Graphite extrusion; Sliding wear; Abrasive wear; Microindentation testing; Microscratch testing
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:hj:diva-24779 (URN)10.1016/j.wear.2014.09.002 (DOI)000345156400015 ()2-s2.0-84907556394 (Scopus ID)
Projects
Helios
Funder
EU, FP7, Seventh Framework Programme, 265861
Available from: 2014-09-21 Created: 2014-09-21 Last updated: 2018-09-14Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-2698-5445

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