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Alternative Ni-based cemented carbide binder – Hardness characterization by nano-indentation and Focused Ion Beam
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 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.     

Place, publisher, year, edition, pages
2017.
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-214101OAI: oai:DiVA.org:kth-214101DiVA: diva2:1140275
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. 50 p.
Keyword
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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