Quantification of nano-scale interface structures to guide mechanistic modelling of WC grain coarsening inhibition in V-doped hard metals

0544716 - ÚJF 2022 RIV GB eng J - Journal Article
Yildiz, A. B. - Babu, R. P. - Bonvalet-Rolland, M. - Busch, S. - Ryukhtin, Vasil - Weidow, J. - Norgren, S. - Hedstrom, P.
Quantification of nano-scale interface structures to guide mechanistic modelling of WC grain coarsening inhibition in V-doped hard metals.
Materials and Design. Roč. 207, SEP (2021), č. článku 109825. ISSN 0264-1275. E-ISSN 1873-4197
Grant - others:AV ČR(CZ) StrategieAV21/23
Program: StrategieAV
Research Infrastructure: Reactors LVR-15 and LR-0 II - 90120; CANAM II - 90056
Institutional support: RVO:61389005
Keywords : hard metals * grain refining * small-angle neutron scattering * computional thermodynamics
OECD category: Materials engineering
Impact factor: 9.417, year: 2021
Method of publishing: Open access
https://doi.org/10.1016/j.matdes.2021.109825

The control of tungsten carbide (WC) grain coarsening using coarsening inhibitors is considered to be one of the most important advancements for hard metals, leading to metal cutting tools with increased performance. Until now, however, the grain coarsening inhibition mechanism for effective inhibitors such as V has been elusive, posing an obstacle to material optimization. This study serves to quantify the presence of nanoscale V-W-C over a wide range of V/Co ratios by small-angle neutron scattering (SANS). The experiments help to delineate how additions of V affect the nanostructure during sintering and result in smaller WC grains. In contrast to the common view that grain coarsening inhibition originates from the presence of stable nanoscale (V,W)C-x complexions formed at the WC/Co interfaces, we show that V segregates at the WC/Co interfaces already upon a minor addition of V and brings significant coarsening inhibition. Increasing additions of V result in the formation of (V,W)C-x complexions, and above 0.76 wt% V addition, where the coverage on WC grains is complete, no further reduction in average grain size is observed. Mechanistic modelling of grain coarsening reveals that grain coarsening inhibition is governed by the reduction of interface mobilities and total driving force for coarsening.
Permanent Link: http://hdl.handle.net/11104/0321541