期刊
INTERNATIONAL JOURNAL OF REFRACTORY METALS & HARD MATERIALS
卷 102, 期 -, 页码 -出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.ijrmhm.2021.105714
关键词
WC grain growth; Apparent activation energy; Cemented carbides; Sintering; WC grain size; Grain size distribution
资金
- Min-istry of Science and Higher Education of the Russian Federation [0718-2020-0034]
The study investigates the kinetics of WC coarsening during the sintering of WC-10 wt% Co cemented carbide grades using various WC powders with different grain sizes and distributions, revealing that different grain characteristics affect the limiting stage of WC coarsening process, corresponding to different physical processes.
Kinetics of WC coarsening during sintering of WC-10 wt% Co cemented carbide grades was examined by use of submicron WC powders with a broad grain size distribution containing much nanograin fraction, medium -finegrain powders with a narrow grain size distribution containing little nanograin fraction and medium-grain powders with a very narrow grain size distribution not containing nanograin fraction. Based on the kinetic curves re-constructed in the Arrhenius coordinates, values of the apparent activation energy for each carbide grade were obtained, which allowed the limiting stage of the WC coarsening process to be evaluated. The limiting stage of the WC coarsening process for the medium-grain grade is related to the diffusion of W and C atoms in the liquid binder during sintering. For the submicron grade the limiting stage of the WC coarsening process is related to interfacial reactions at WC/liquid interfaces. In this case, the diffusion of W and C atoms dissolved in the liquid binder is fast due to a very significant difference between sizes of the fine/nano WC grains and coarser WC grains. When increasing the sintering temperature and time above a certain level, the significant acceleration of WC coarsening takes place indicating the transition of the process to the stage of anomalous grain growth, at which the formation of abnormally large WC grains in the microstructure determines the whole WC coarsening process. The limiting stage of the WC coarsening process for the medium-fine-grain grade is mainly related to diffusion of W and C atoms dissolved in the liquid binder.
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