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ICME guided development of cemented carbides with alternative binder systems
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The development of alternative binder systems for tungsten carbide (WC) based cemented carbides has again become of relevance due to possible changes in EU regulations regarding the use of Cobalt (Co). A framework for the ICME (Integrated Computational Materials Engineering) based Materials Design is presented to accelerate the development of alternative binder systems.

Part one of this work deals with the design of the cemented carbide composite hardness. It has been shown that the intrinsic binder hardness is comparable to a bulk metal alloy and that based on the binder solubilities a solid solution strengthening model developed in this work can be employed. Using a method presented in this work the non-equilibrium, frozen-in binder solubilities can be obtained. Both the design of the binder phase and composite hardness is presented based on a general Materials Design approach.

Part two deals with a multiscale approach to model the surface gradient formation. The experimentally missing data on liquid binder diffusion has been calculated using AIMD (Ab initio Molecular Dynamics). The diffusion through the liquid cemented carbide binder has to be reduced to an effective diffusion value due to the solid carbides acting as obstacles that increase the diffusion path. The geometrical reduction of the diffusion has been investigated experimentally using the SIMS (secondary ion mass spectroscopy) technique in WC-Nickel-58Nickel diffusion couples. The geometrical contribution of the so-called labyrinth factor has been proven by the combination of the experiments and in conjunction with DICTRA simulations using the precise liquid AIMD diffusivities. Unfortunately, despite the improved kinetic database and the geometrical diffusion reduction, the surface gradient formation cannot be explained satisfactory in complex cemented carbide grades. Additional, but so far unidentified, contributions have to be considered to predict the surface gradient thickness.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. , p. 50
Keywords [en]
Cemented carbide, ICME, Materials Design, alternative binder, hardness, AIMD, liquid diffusion, frozen-in solubilities, DICTRA, surface gradients, labyrinth factor
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
URN: urn:nbn:se:kth:diva-214108ISBN: 978-91-7729-511-2 (print)OAI: oai:DiVA.org:kth-214108DiVA, id: diva2:1142092
Public defence
2017-10-23, F3, Lindstedsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20170919

Available from: 2017-09-19 Created: 2017-09-18 Last updated: 2019-12-20Bibliographically approved
List of papers
1. Diffusion modeling in cemented carbides: Solubility assessment for Co, Fe and Ni binder systems
Open this publication in new window or tab >>Diffusion modeling in cemented carbides: Solubility assessment for Co, Fe and Ni binder systems
2017 (English)In: International Journal of Refractory Metals and Hard Materials, ISSN 0263-4368, Vol. 68, p. 41-48Article in journal (Refereed) Published
Abstract [en]

The increasing interest in alternative binder solutions for WC based cemented carbide systems leads to more integration of ICME (Integrated Computational Materials Engineering) based concepts in the materials development. This work investigates the non-equilibrium W and C solubilities upon furnace-cooling in a wide range of Co and Fe-Ni based binder systems by computational means. It is shown that the solubilities strongly depend on the C-activity and binder matrix elements, revealing that Ni dissolves most W and Fe most C out of the investigated systems. Furthermore, the effect of the binder mean free path and the cooling rates on the solubilities was investigated. The presented method and results provide insights to control the binder chemistry and will help to design the properties for future binder systems in a fast and efficient way.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Alternative binder, Cemented carbides, DICTRA, ICME, Non-equilibrium solubility, Binary alloys, Binders, Carbide tools, Carbides, Cobalt alloys, Cooling systems, Iron alloys, Nickel, Nickel alloys, Solubility, Tungsten carbide
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-212205 (URN)10.1016/j.ijrmhm.2017.06.006 (DOI)000410014600006 ()2-s2.0-85021623942 (Scopus ID)
Note

QC 20170821

Available from: 2017-08-21 Created: 2017-08-21 Last updated: 2019-12-20Bibliographically approved
2. Alternative Ni-based cemented carbide binder – Hardness characterization by nano-indentation and Focused Ion Beam
Open this publication in new window or tab >>Alternative Ni-based cemented carbide binder – Hardness characterization by nano-indentation and Focused Ion Beam
2017 (English)In: Article in journal (Other academic) Submitted
Abstract [en]

The nano-hardness in the alternative 85Ni-15Fe binder phase of WC cemented carbide has been investigated. High-resolution scanning electron microscopy (SEM) imaging was used to measure the projected indentation area and a general pile-up correction, confirmed on selected indents, has been employed using atomic force microscopy (AFM). Focused ion-beam (FIB) cross-sections have been used to investigate the binder morphology below the indentations and the local binder hardness has been associated to the distance to the surrounding WC grains. Generally, decreasing distance to the WC grains leads to increased binder hardness. Furthermore, the nano-hardness for the cemented carbide binder has been corrected for the indentation size effect (ISE) to obtain the corresponding macroscopic hardness. A solid solution strengthening model for multicomponent bulk alloys was used to calculate the expected binder Vickers hardness considering the binder solubilites of W and C. Both the strengthening model and the ISE corrected hardness values, for larger binder regions, are in good agreement indicating that the intrinsic binder phase hardness is similar to that of a bulk metal alloy with similar composition.     

National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-214101 (URN)
Note

QCR 20170913

Available from: 2017-09-11 Created: 2017-09-11 Last updated: 2019-12-20Bibliographically approved
3. Modelling of solid solution strengthening in multicomponent alloys
Open this publication in new window or tab >>Modelling of solid solution strengthening in multicomponent alloys
2017 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 700, p. 301-311Article in journal (Refereed) Published
Abstract [en]

With increasing industrial interest in high alloyed multicomponent and High Entropy Alloy (HEA) systems the integration of solid solution strengthening in the ICME framework for efficient Materials Design becomes an important translator tool. A general model is proposed that performs as the framework for an extensive assessment of solid solution strengthening coefficients. The model assumes the concentration dependence of x(2/3) as proposed by Labusch but gives a non-linear composition dependence to the strengthening parameter yielding a better description for concentrated alloys. To calibrate the model, 895 alloy systems, including a wide range of elements, have been used giving a good agreement between calculated and experimental values. Additionally, a promising method is proposed to represent the temperature related softening in the investigated systems.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2017
Keywords
Materials design, Solid solution strengthening, ICME, Multicomponent alloys, Translator, HEA
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-213809 (URN)10.1016/j.msea.2017.06.001 (DOI)000406564300036 ()2-s2.0-85020482202 (Scopus ID)
Note

QC 20170911

Available from: 2017-09-11 Created: 2017-09-11 Last updated: 2019-12-20Bibliographically approved
4. A new hardness model for Materials Design in Cemented Carbides
Open this publication in new window or tab >>A new hardness model for Materials Design in Cemented Carbides
2017 (English)In: Article in journal (Other academic) Submitted
Abstract [en]

The Materials Design approach offers new possibilities towards property oriented materials development. The performance of cemented carbides is significantly influenced by properties like hardness and fracture toughness. Fundamental models, which allow for prediction of the properties of interest, make it possible to tailor the properties of the material based on the required performance. None of the previously available models are suitable to actively design the cemented carbide hardness because they are valid only for Co binders and do not allow alternative binder phases. The hardness is greatly influenced by the chemistry, binder volume fraction and carbide grain size. Only the chemistry, specifically the binder composition, leaves the possibility to optimize the binder hardness and to exceed classical WC-Co cemented carbides. Specifically focusing on the design of the binder phase, a new description of the binder hardness is implemented in a modified Engqvist hardness model and allows for the prediction of a wider range of conventional and alternative systems. The model was validated for various published cemented carbide systems and is able to predict their hardness within a 10% error. The assessed systems contain classical Co binders as well as alternative, austenitic binders based on Fe, Ni and Co.

National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-214102 (URN)
Note

QC 20170913

Available from: 2017-09-11 Created: 2017-09-11 Last updated: 2019-12-20Bibliographically approved
5. Surface gradients in cemented carbides from first-principles-based multiscale modeling: Atomic diffusion in liquid Co
Open this publication in new window or tab >>Surface gradients in cemented carbides from first-principles-based multiscale modeling: Atomic diffusion in liquid Co
2017 (English)In: International Journal of Refractory Metals and Hard Materials, ISSN 0263-4368, Vol. 66, p. 174-179Article in journal (Refereed) Published
Abstract [en]

The kinetic modeling of cemented carbides, where Co is used as binder element, requires a detailed diffusion description. Up to now, no experimental self- or impurity diffusion data for the liquid Co system have been available. Here we use the fundamental approach based on ab initio molecular dynamics simulations to assess diffusion coefficients for the liquid Co system, including six solute elements. Our calculated Co self-diffusion coefficients show good agreement with the estimates that have been obtained using scaling laws from the available literature data. To validate the modeling method, we performed one set of calculations for liquid Ni self-diffusion, where experimental data are available, showing good agreement between theory and experiments. The computed diffusion data were used in subsequent DICTRA simulations to model the gradient formation in cemented carbide systems. The results based on the new diffusion data allows for correct predictions of the gradient thickness.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Ab initio molecular dynamics, Cemented carbides, DICTRA, Diffusion, ICME, Liquid co, Calculations, Carbide tools, Carbides, Diffusion in liquids, Diffusion in solids, Liquids, Molecular dynamics
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-207284 (URN)10.1016/j.ijrmhm.2017.03.016 (DOI)000418222000025 ()2-s2.0-85016489381 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20170619

Available from: 2017-06-19 Created: 2017-06-19 Last updated: 2018-01-09Bibliographically approved
6. Atomic Diffusion in Liquid Nickel: First-principles Modeling
Open this publication in new window or tab >>Atomic Diffusion in Liquid Nickel: First-principles Modeling
2017 (English)In: Article in journal (Other academic) Submitted
Abstract [en]

Self- and impurity diffusion coefficients are assessed in the liquid Nickel system by the fundamental ab initio molecular dynamics approach (AIMD). The impurity diffusion coefficients in the Ni-X systems (X=C, Co, N, Nb, Ta, Ti, W) are mostly not available in the current literature. The simulations are performed at four temperatures, in the range from 1903 to 2303 K, which allows to extract activation energies and frequency factors for the temperature dependent diffusion coefficient assuming an Arrhenius-type behavior in the liquid. In addition to the temperature dependence, the concentration-dependent impurity diffusion was investigated for the Ni-Co system. The data are of relevance for the development of state-of-the art Ni-based superalloys and alternative binder systems in cemented carbides. The obtained theoretical results are in very good agreement with the limited experimental data for the diffusion in liquid Ni systems.

National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-214103 (URN)
Note

QCR 20170913

Available from: 2017-09-11 Created: 2017-09-11 Last updated: 2017-09-18Bibliographically approved
7. Effective diffusion in cemented carbide systems: Geometrical effect of the labyrinth factor
Open this publication in new window or tab >>Effective diffusion in cemented carbide systems: Geometrical effect of the labyrinth factor
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In cemented carbides the effective diffusivities are associated with the carbides acting as obstacles that increase the diffusion distance, thus altering the overall diffusion in the composite. From an industrial point of view, the prediction of the surface gradient formation is important to develop state-of-the-art cemented carbide cutting tools and require an understanding of the liquid binder diffusivities and the effective diffusion reduction at typical sintering temperatures where the binder is molten. Recently, a full description of the diffusivities in the liquid binder has become available and the focus of the present work is thus the effective diffusion reduction. Isotope diffusion couple experiments have been successfully performed to investigate the effective diffusion in a WC-Ni liquid binder-carbide composite material, i.e. a cemented carbide. The 58Ni isotope diffusion profiles have been measured with Secondary Ion Mass Spectroscopy (SIMS) and the results have been compared to DICTRA simulations using an updated kinetic database. The agreement between the experimental and simulated diffusion profiles is excellent showing that the theoretical geometrical limit, simulated with the upper Hashin-Shtrikman bound, is obeyed in simple cemented carbide systems. For complex cemented carbide systems, where gradient sintering is relevant, the effective diffusion is insufficiently explained by the geometrical reduction.

National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-214105 (URN)
Note

QC 20170919

Available from: 2017-09-11 Created: 2017-09-11 Last updated: 2017-09-19Bibliographically approved

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