A computational study of special grain boundaries in WC–Co cemented carbides

Johansson, Sven; Petisme, Martin; Wahnström, Göran

doi:10.1016/j.commatsci.2014.11.024

Cited by 20 publications

(9 citation statements)

References 45 publications

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“…The segregation width measured in the present work (0.6-08 ML) is in good agreement with previous experimental studies, especially carried out by APT [27,28] as well as by atomistic modelling [49,23]. Also, no segregation is detected in the special Σ=2 grain boundary as predicted by calculations [50]. It can be observed that although the analyses are not fully quantitative, the method leads to valid estimates of the segregation in grain boundaries.…”

Section: Discussionsupporting

confidence: 92%

Interface characteristics in cemented carbides with alternative binders

Roulon

Lay

Missiaen

2020

International Journal of Refractory Metals and Hard Materials

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Cemented tungsten carbides with Co, Ni or Fe binders were studied by transmission electron microscopy.Particular attention was paid to phase and grain boundaries. A striking feature is the high frequency of coherent carbide/binder interfaces with Fe. The Fe rich binder adopts an epitaxy orientation relationship with prismatic facets of WC, with a parametric misfit of about 1.5%. A special orientation relationship with basal facets of WC grains is sometimes observed with Ni binder, as already noticed for Co. It is associated with a parametric misfit of about 15%. Binder segregation in WC grain boundaries was studied taking into account the effect of carbon content in the alloys. Whatever the binder, no influence of the carbon content could be pointed out. The analyses performed in random grain boundaries in WC-Co alloys agree with the literature value of 0.5 monolayer of segregated Co while slightly larger values are obtained for Ni and Fe binder. ∑=2 special grain boundaries were studied in WC-Co and WC-Ni alloys and no segregation was detected. The higher grain boundary segregation as well as the occurrence of coherent interfaces should influence the mechanical properties of WC-Fe alloys.

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Section: Discussionsupporting

confidence: 92%

Interface characteristics in cemented carbides with alternative binders

Roulon

Lay

Missiaen

2020

International Journal of Refractory Metals and Hard Materials

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“…In the c/a = 1 approximation, WC/WC grain boundaries can be classified in terms of their coincidence index defined as the inverse of the fraction of lattice sites that coincide when two lattices are superimposed [20]. The most common as well as the most investigated WC/WC grain boundary is the 90 • /[ 1 1 0 0] twist grain boundary [21,22] which has = 2. In [8], 11-14% of WC/WC grain boundaries were found to be of this type.…”

Section: Grain and Phase Boundariesmentioning

confidence: 99%

“…These = 2 grain boundaries are already present in the powder [23] and during sintering they tend to straighten out and predominantly be of pure twist type [24]. The = 2 twist grain boundary is associated with low interfacial energy [18,22]. They do not contribute in an essential way to the formation of the final continuous network of hard WC grains and, therefore, they are not a good choice of model for a more general grain boundary relevant to studying the final mechanical strength of the material.…”

Section: Grain and Phase Boundariesmentioning

confidence: 99%

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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“…In the present study, MD simulations were performed using the large-scale atomic/molecular massively parallel simulator open-source code (Plimpton, 1995) with analytical bond-order potential Petisme, Gren, & Wahnströ m, 2015;Johansson et al, 2015;Albe et al, 2002;Erhart & Albe, 2005;Bjö rkas et al, 2009;Li et al, 2011;Ercolessi & Adams, 1994) for the W-C-Co system. Firstly, the modeled bulk was relaxed at 300 K for 100 ps to reach equilibrium, which was achieved by using an isothermal-isobaric ensemble via a Nosé -Hoover thermostat (Nosé, 1984;Hoover, 1985).…”

Section: Molecular Dynamics Simulation Methodsmentioning

confidence: 99%

Crystal defects responsible for mechanical behaviors of a WC–Co composite at room and high temperatures – a simulation study

Fang

Liu

et al. 2019

Acta Crystallogr B Struct Sci Cryst Eng Mater

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The microstructure evolution and changes in the structures of crystal defects of the nanocrystalline WC-Co composite in the process of uniaxial compression were studied by simulations at both room and high temperatures. The deformation processes were demonstrated as a function of stress and temperature for the stages prior to and after yielding of the composite. The Peierls stresses were evaluated for Co and WC dislocations with increasing temperature. The deformation mechanisms for each stage of the stress-strain curve were disclosed, in which the effect of temperature was clarified. It was found that with the increase of stress, from elastic deformation to plastic deformation then to yielding of the composite, the dominant mechanisms are grain boundary migration, formation and motion of dislocations in Co, concurrent motion and reaction of dislocations in Co and WC, and then rotation of WC grains in combination with motion of Co and WC dislocations. At the yielding stage, sliding of WC grain boundaries plays an increasingly important role in the contribution to plastic deformation at high temperatures. With strain the proportion of mobile dislocations decreases, and dislocations pile up at triple junctions of WC grains, WC/WC grain boundaries and WC/Co phase boundaries in priority order, leading to the nucleation and propagation of microcracks in these regions.

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A computational study of special grain boundaries in WC–Co cemented carbides

Cited by 20 publications

References 45 publications

Interface characteristics in cemented carbides with alternative binders

Interface characteristics in cemented carbides with alternative binders

A computational study of interfaces in WC–Co cemented carbides

Crystal defects responsible for mechanical behaviors of a WC–Co composite at room and high temperatures – a simulation study

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