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A new hardness model for Materials Design in Cemented Carbides
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. (Enheten strukturer)
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. (Enheten strukturer)
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. (Enheten strukturer)
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. (Enheten strukturer)
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.

Place, publisher, year, edition, pages
2017.
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-214102OAI: oai:DiVA.org:kth-214102DiVA, id: diva2:1140276
Note

QCR 20170913

Available from: 2017-09-11 Created: 2017-09-11 Last updated: 2017-09-18Bibliographically approved
In thesis
1. ICME guided development of cemented carbides with alternative binder systems
Open this publication in new window or tab >>ICME guided development of cemented carbides with alternative binder systems
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
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:nbn:se:kth:diva-214108 (URN)978-91-7729-511-2 (ISBN)
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: 2017-09-20Bibliographically approved

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