APT analysis of WC–Co based cemented carbides

Weidow, Jonathan; Andrén, Hans-Olof

doi:10.1016/j.ultramic.2011.01.033

Cited by 15 publications

(5 citation statements)

References 24 publications

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“…Co segregation is predicted to all model WC/WC grain boundaries in 0.5 monolayer proportion, in accordance with experiments [26,73]. The average grain boundary energy taking this into account is 2.3 J m −2 .…”

Section: Discussionsupporting

confidence: 86%

A computational study of interfaces in WC–Co cemented carbides

Petisme

Johansson

Wahnström

2015

Modelling Simul. Mater. Sci. Eng.

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Interfaces in WC–Co cemented carbides have been investigated using the density functional theory (DFT). Six different model WC/WC grain boundaries are considered, together with the corresponding WC surfaces and WC/Co phase boundaries. The contribution to the grain boundary energies arising from misfit is estimated using an analytical bond order potential (ABOP) and the effect of magnetism is investigated using spinpolarized and non-spinpolarized calculations. A systematic study of adsorption of Co to WC surfaces, Co segregation to WC/WC grain boundaries and Co substitution at WC/Co phase boundaries has been carried out. Adsorption of Co to most WC surfaces is predicted, and result in a monolayer coverage of Co and sometimes a mixed Co/W or Co/W monolayer. The WC surfaces will become prewetted with Co as soon as the atoms become mobile at finite temperatures. Co substitutional segregation is predicted to all model WC/WC grain boundaries in 0.5 monolayer proportion. The segregation of Co to grain boundaries stabilizes the continuous skeleton network of hard WC grains in cemented carbides. Using the obtained interfacial energies, the wetting and the driving force for cobalt grain boundary infiltration are discussed. A dependence on the wetting efficiency on the carbon chemical potential is predicted, which could be an explanation for the better wetting observed experimentally under W-rich conditions.

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Section: Discussionsupporting

confidence: 86%

A computational study of interfaces in WC–Co cemented carbides

Petisme

Johansson

Wahnström

2015

Modelling Simul. Mater. Sci. Eng.

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“…In the case of M23C6 the steel sample had to be carefully ion milled until a carbide could be observed close to the tip apex. Needle samples of WC were prepared by a combination of electropolishing and FIB [21]. In all cases the final milling was carried out using a lower voltage (5 kV) to limit Ga implantation.…”

Section: Methodsmentioning

confidence: 99%

Quantitative atom probe analysis of carbides

et al. 2011

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Compared to atom probe analysis of metallic materials, the analysis of carbide phases results in an enhanced formation of molecular ions and multiple events. In addition, many multiple events appear to consist of two or more ions originating from adjacent sites in the material. Due to limitations of the ion detectors measurements generally underestimate the carbon concentration. Analyses using laser-pulsed atom probe tomography have been performed on SiC, WC, Ti(C,N) and Ti(2)AlC grains in different materials as well as on large M(23)C(6) precipitates in steel. Using standard evaluation methods, the obtained carbon concentration was 6-24% lower than expected from the known stoichiometry. The results improved remarkably by using only the (13)C isotope, and calculating the concentration of (12)C from the natural isotope abundance. This confirms that the main reason for obtaining a too low carbon concentration is the dead time of the detector, mainly affecting carbon since it is more frequently evaporated as multiple ions. In the case of Ti(C,N) and Ti(2)AlC an additional difficulty arises from the overlap between C(2)(+), C(4)(2+) and Ti(2+) at the mass-to-charge 24 Da.

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“…APT specimens of materials C1 and C3 were produced through a combination of electropolishing, back polishing and ion polishing [11]. The specimens were analyzed in an Imago LEAP 3000X HR instrument using 200 kHz 0.35 nJ laser pulsing with the specimen temperature at 66 K. The data was analyzed using the Imago IVAS 3.4.3 software.…”

Section: Experimental and Theoretical Detailsmentioning

confidence: 99%