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Wang, W., Hou, Z., Lizarrága, R., Tian, Y., Babu, P., Holmström, E., . . . Larsson, H. (2019). An experimental and theoretical study of duplex fcc+hcp cobalt based entropic alloys. Acta Materialia, 176, 11-18
Open this publication in new window or tab >>An experimental and theoretical study of duplex fcc+hcp cobalt based entropic alloys
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2019 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 176, p. 11-18Article in journal (Refereed) Published
Abstract [en]

Martensitically formed duplex fcc + hcp Co-based entropic alloys have been investigated both experimentally and theoretically. Theoretical predictions are in good agreement with experimental observations. A fair correlation is found between calculated driving forces for a partitionless fcc→hcp transformation and experimentally obtained phase fractions.

Place, publisher, year, edition, pages
Elsevier, 2019
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-258027 (URN)10.1016/j.actamat.2019.06.041 (DOI)2-s2.0-85068362090 (Scopus ID)
Note

QC 20190917

Available from: 2019-09-09 Created: 2019-09-09 Last updated: 2019-09-17Bibliographically approved
Salmasi, A., Blomqvist, A. & Larsson, H. (2019). Geometry effects during sintering of graded cemented carbides: Modelling of microstructural evolution and mechanical properties. Results in Materials, 1, Article ID 100008.
Open this publication in new window or tab >>Geometry effects during sintering of graded cemented carbides: Modelling of microstructural evolution and mechanical properties
2019 (English)In: Results in Materials, ISSN 2590-048X, Vol. 1, article id 100008Article in journal (Refereed) Published
Abstract [en]

Cemented carbides with mesoscopically non-homogeneous properties by design represent a potential to enhanceperformance in metal cutting and rock drilling. Development of in-homogeneous structured hard materialsthrough an ICME approach requires a thorough understanding of diffusion kinetics during solid and liquid statesintering. In this work, we used thermodynamics and diffusion kinetics modelling tools to predict the micro-structure and resulting properties of cemented carbide composites. First, we designed and gradient sintered two(WC-TiCN-Co) cemented carbides with different nitrogen to titanium ratios. Second, we reproduced the experi-mental results in 2D by means of thermodynamic and kinetic simulations. In the last step we calculated fracturetoughness KIC, and Vickers hardness of cemented carbides. The agreement between simulations and experimentalresults is fair and acceptable

Keywords
ICME Diffusion Cemented carbides Gradient sintering Hardness Fracture toughness
National Category
Engineering and Technology
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-258031 (URN)10.1016/j.rinma.2019.100008 (DOI)
Projects
Sintring av inhomogena strukturer för förbättra prestanda
Funder
Swedish Foundation for Strategic Research , RMA15-0062
Note

QC 20190916

Available from: 2019-09-09 Created: 2019-09-09 Last updated: 2019-09-16Bibliographically approved
Forslund, A. & Larsson, H. (2019). Simulation of reaction-diffusion between substrate and coating during vapor deposition processes. Calphad, 64, 278-283
Open this publication in new window or tab >>Simulation of reaction-diffusion between substrate and coating during vapor deposition processes
2019 (English)In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 64, p. 278-283Article in journal (Refereed) Published
Abstract [en]

This work presents simulations of the solid state diffusion and reactions during deposition processes. Two cases are studied where the diffusion in and between coating and substrate is simulated. The processes simulated are in one case directed vapor deposition of Al and Ni on a precoated nickel-base superalloy, and in the other case chemical vapor deposition aluminization of a nickel-base superalloy. The simulations result in composition and phase-fraction profiles, which are presented and compared with experimental composition profiles. The simulation results are generally in good agreement with the experimental profiles.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2019
Keywords
Simulation, Diffusion, Nickel-base superalloy, Chemical vapor deposition, Directed vapor deposition
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-247819 (URN)10.1016/j.calphad.2018.12.014 (DOI)000460842600029 ()2-s2.0-85059562570 (Scopus ID)
Note

QC 20190327

Available from: 2019-03-27 Created: 2019-03-27 Last updated: 2019-04-04Bibliographically approved
Holmström, E., Lizarraga, R., Linder, D., Salmasi, A., Wang, W., Kaplan, B., . . . Vitos, L. (2018). High entropy alloys: Substituting for cobalt in cutting edge technology. Applied Materials Today, 12, 322-329
Open this publication in new window or tab >>High entropy alloys: Substituting for cobalt in cutting edge technology
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2018 (English)In: Applied Materials Today, ISSN 2352-9407, Vol. 12, p. 322-329Article in journal (Refereed) Published
Abstract [en]

Cemented carbide, also known as hard metal, is one of the most outstanding composite engineering materials since its commercial introduction in the 1920s. The unique combination of strength, hardness and toughness makes cemented carbides highly versatile materials for the most demanding engineering applications. In their simplest form, these materials are composites of tungsten carbide (WC) grains that are cemented with a ductile metallic binder phase, typically cobalt. However, despite the superiority of Co as binder material, there is a long-standing need to find alternative binders due to serious health concerns that have haunted the industry for nearly 80 years. In the present study, we develop a new cemented carbide with a high entropy alloy binder phase (CoCrFeNi) from raw materials to a fully functional, coated and gradient-sintered cutting tool insert. The new hard metal with reduced Co content is designed by using first principles theory and the CALPHAD method. The cutting tool was made by pressing the new hard metal in a standard geometry, sintered to have a thin binder phase enriched surface zone, free from cubic carbides and coated with protective layers of Ti(C,N) and Al2O3. The resulting cutting insert was tested in a real machining operation and compared to a state-of-the-art reference that had Co as binder phase. The cutting tool made of the newly developed cemented carbide has an exceptionally high resistance against plastic deformation at all tested cutting speeds in the machining test, outperforming the reference insert, which shows a linear increase in edge depression when the cutting speed is increased. This result opens up the possibility to utilize the unique properties of high entropy alloys for industrial applications, in particular, as binder phase in new cemented carbides.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
High entropy alloys, Cemented carbides, Cobalt binder, Alternative binders, Density functional theory, Calphad
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-235109 (URN)10.1016/j.apmt.2018.07.001 (DOI)000443213700028 ()2-s2.0-85049613452 (Scopus ID)
Funder
VINNOVA, 2016-00805Swedish Research CouncilSwedish Foundation for Strategic Research The Swedish Foundation for International Cooperation in Research and Higher Education (STINT)Carl Tryggers foundation
Note

QC 20180919

Available from: 2018-09-19 Created: 2018-09-19 Last updated: 2018-11-13Bibliographically approved
Walbrühl, M., Ågren, J., Blomqvist, A. & Larsson, H. (2018). ICME guided modeling of surface gradient formation in cemented carbides. International Journal of Refractory Metals and Hard Materials, 72, 33-38
Open this publication in new window or tab >>ICME guided modeling of surface gradient formation in cemented carbides
2018 (English)In: International Journal of Refractory Metals and Hard Materials, ISSN 0263-4368, Vol. 72, p. 33-38Article in journal (Refereed) Published
Abstract [en]

Structural gradients are of great interest for state-of-the-art cemented carbides used in metal cutting applications. The gradient growth during sintering is controlled by the fundamental aspects of diffusion, thermodynamics and phase equilibria in systems with multiple components and phases. With the demand for binder alternatives to Co, there is a need for understanding the diffusion and thermodynamics in new materials systems. Materials development guided by ICME (Integrated Computational Materials Engineering) is a new approach that accelerates the design of tailor-made materials, assisting us to find and optimize prospective binder candidates using computational tools. The role of the thermodynamic descriptions will be briefly discussed but this work focuses on a better kinetic description. Models based on cemented carbide microstructures and fundamental understanding of kinetics will allow for a more general use of simulations of gradient formation. The diffusion of elements during sintering mainly occurs in the liquid binder phase, with the solid WC and gamma phases acting as an effective labyrinth, hindering diffusion. In this work, the liquid mobilities and the effective labyrinth factor is studied for traditional and alternative binders by combing ab initio molecular dynamics and diffusion couple experiments with CALPHAD modeling. 

Place, publisher, year, edition, pages
Elsevier Ltd, 2018
Keywords
AIMD, DICTRA, ICME, Labyrinth factor, Liquid diffusion, Surface gradients, Bins, Carbide tools, Carbides, Diffusion, Liquids, Metal cutting, Molecular dynamics, Phase equilibria, Sintering, Thermodynamics, Binders
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-223113 (URN)10.1016/j.ijrmhm.2017.12.010 (DOI)000427209100006 ()2-s2.0-85038021984 (Scopus ID)
Note

Export Date: 13 February 2018; Article; CODEN: IJRMD; Correspondence Address: Walbrühl, M.; Department of Materials Science and Engineering, Royal Institute of TechnologySweden; email: walbruhl@kth.se; Funding details: KTH, Kungliga Tekniska Högskolan; Funding details: VINNOVA. QC 20180227

Available from: 2018-02-27 Created: 2018-02-27 Last updated: 2018-05-24Bibliographically approved
Larsson, H. & Agren, J. (2017). Simulation of Coupled Carbonitriding and Internal Oxidation of Steel. HTM-JOURNAL OF HEAT TREATMENT AND MATERIALS, 72(1), 19-24
Open this publication in new window or tab >>Simulation of Coupled Carbonitriding and Internal Oxidation of Steel
2017 (English)In: HTM-JOURNAL OF HEAT TREATMENT AND MATERIALS, ISSN 1867-2493, Vol. 72, no 1, p. 19-24Article in journal (Refereed) Published
Abstract [en]

Carbonitriding and internal oxidation have been simulated simultaneously using the DICTRA homogenization model. The predicted carbon and nitrogen profiles as well as the oxide and nitride phase fraction profiles agree favourably with experimental data obtained from the literature, though some discrepancies exist. The present approach should be a very useful tool in process control and optimization.

Place, publisher, year, edition, pages
CARL HANSER VERLAG, 2017
Keywords
Carbonitriding, internal oxidation, simulation
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-205138 (URN)10.3139/105.110313 (DOI)000397219700004 ()2-s2.0-85015798578 (Scopus ID)
Note

QC 20170412

Available from: 2017-04-12 Created: 2017-04-12 Last updated: 2017-06-29Bibliographically approved
Larsson, H., Jonsson, T., Naraghi, R., Gong, Y., Reed, R. C. & Ågren, J. (2016). Oxidation of iron at 600 degrees C - experiments and simulations. Materials and corrosion - Werkstoffe und Korrosion
Open this publication in new window or tab >>Oxidation of iron at 600 degrees C - experiments and simulations
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2016 (English)In: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176Article in journal (Refereed) Published
Abstract [en]

Pure iron has been oxidized at 600°C and 1bar in dry O2 (oxygen partial pressure 0.05, bal. N2) and the mass gain as well as the thicknesses of the individual oxide phases have been measured. The oxidation process has been simulated using a modified version of the homogenization model as implemented in Dictra; this has helped to rationalize the kinetics of oxide scale formation and in particular the evolution of the hematite (Fe2O3), magnetite (Fe3O4), and wustite (FeO) which form. Independently assessed thermodynamic and kinetic Calphad databases are needed for the calculations; details of these are given. Reasonable agreement between simulation results and experimental data is obtained, though it is concluded that the large influence of grain boundary diffusion on the oxidation rate needs further consideration.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2016
Keywords
Calphad, Iron, Modeling, Oxidation, Simulation, Grain boundaries, Models, Scale (deposits), Grain-boundary diffusion, Oxidation process, Oxidation rates, Oxide phasis, Oxide scale formations, Oxygen partial pressure
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-186758 (URN)10.1002/maco.201508781 (DOI)000394663600003 ()2-s2.0-84964355248 (Scopus ID)
Note

QC 20160530

Available from: 2016-05-30 Created: 2016-05-13 Last updated: 2017-11-30Bibliographically approved
Hatt, O., Larsson, H., Giuliani, F., Crawforth, P., Wynne, B. & Jackson, M. (2016). Predicting Chemical Wear in Machining Titanium Alloys Via a Novel Low Cost Diffusion Couple Method. In: Procedia CIRP: . Paper presented at 3rd CIRP Conference on Surface Integrity, CIRP CSI 2016, 8 June 2016 through 10 June 2016 (pp. 219-222). Elsevier
Open this publication in new window or tab >>Predicting Chemical Wear in Machining Titanium Alloys Via a Novel Low Cost Diffusion Couple Method
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2016 (English)In: Procedia CIRP, Elsevier, 2016, p. 219-222Conference paper, Published paper (Refereed)
Abstract [en]

Chemical wear during high speed machining of titanium alloys is a serious problem which affects the surface integrity of both the tool and workpiece. A low cost, novel diffusion couple method is presented which allows for thorough analysis of the tool-workpiece interface at the high temperatures reached during conventional machining operations. X-EDS analysis reveals that no less than seven distinct diffusion zones arise between Ti-6Al-4 V and a WC-Co tool which are home to different phases and reaction species. Loss of cobalt binder coupled with a deficit of carbon results in a brittle η-phase leading to catastrophic fracturing of the tool. DICTRA is employed to thermodynamically model the diffusion mechanisms and verify the X-EDS results.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Alloy chemistry, Alloy design, DICTRA, Diffusion, Machining, Titanium, Tool wear, Carbide cutting tools, Carbon, Cost benefit analysis, Cutting tools, Alloy designs, Conventional machining, Diffusion mechanisms, High speed machining, Surface integrity, Titanium alloys
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-195435 (URN)10.1016/j.procir.2016.01.196 (DOI)000417326500055 ()2-s2.0-84978643573 (Scopus ID)
Conference
3rd CIRP Conference on Surface Integrity, CIRP CSI 2016, 8 June 2016 through 10 June 2016
Note

QC 20161128

Available from: 2016-11-28 Created: 2016-11-03 Last updated: 2019-10-18Bibliographically approved
Larsson, H. & Höglund, L. (2015). A scheme for more efficient usage of CALPHAD data in simulations. Calphad, 50, 1-5
Open this publication in new window or tab >>A scheme for more efficient usage of CALPHAD data in simulations
2015 (English)In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 50, p. 1-5Article in journal (Refereed) Published
Abstract [en]

A method is suggested that allows thermodynamic data to be dynamically stored and retrieved. The purpose of the method is to reduce computer simulation time when Calphad type databases are being used. Some test simulations are presented and these indicate that simulations can be made to run 5-40 times faster without any significant loss of accuracy.

Keywords
CALPHAD, Computational modeling, Simulation
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-172664 (URN)10.1016/j.calphad.2015.04.007 (DOI)000358467900001 ()2-s2.0-84929081902 (Scopus ID)
Note

QC 20150901

Available from: 2015-09-01 Created: 2015-08-27 Last updated: 2017-12-04Bibliographically approved
Warnken, N., Larsson, H. & Reed, R. C. (2009). Coupled modelling of solidification and solution heat treatment of advanced single crystal nickel base superalloy. Materials Science and Technology, 25(2), 179-185
Open this publication in new window or tab >>Coupled modelling of solidification and solution heat treatment of advanced single crystal nickel base superalloy
2009 (English)In: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 25, no 2, p. 179-185Article in journal (Refereed) Published
Abstract [en]

Two numerical models to simulate microsegregation and phase formation during directional solidification and subsequent solution heat treatment of an advanced experimental ruthenium containing single crystal nickel base superalloy are tested and compared. The first method is based on a one-dimensional front tracking for the primary solidification and a homogenisation method for the final stages of solidification as well as for the solution heat treatment. Calculations for this model are carried out in one-dimension using cylindrical coordinates. The second is based upon the phase field method, applied to solidification and subsequent solution heat treatment, where calculations are carried out in two-dimension. Both models are coupled to thermodynamic and kinetics databases modelled according to the CALPHAD method. A concept of computer based optimisation of solution heat treatments is proposed. The results show that both methods are capable of handling the complexity of contemporary superalloys, and realistic results are obtained from both models.

Keywords
Simulation, Phase field, Front tracking, Solidification, Solution heat, treatment, Superalloy, Thermodynamics, Microstructure modelling
Identifiers
urn:nbn:se:kth:diva-18153 (URN)10.1179/174328408x369320 (DOI)000263100600008 ()2-s2.0-60549117969 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-8797-4585

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