Structure and Properties of Coarse-Grained WC–Co Alloys with an Especially Homogeneous Microstructure


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Abstract

The structure and properties of coarse-grained WC–6% Co carbides with carbon deficiency from 0.11 to 1.31% relative to the stoichiometric ration prepared from narrow-fraction tungsten carbide powder with a grain size of 5–15 μm are studied. It is established by the results of metallographic analysis that sintering temperatures in a range of 1390–1420°C provide the pore-free state of the alloy with the normal carbon content, but the samples have considerable porosity at its lowered concentrations. It is revealed that sintering temperatures of 1450–1475°C, irrespective of the carbon content, make it possible to prepare carbides with residual porosity lower than 0.02%. It is shown that alloys with a carbon deficit of 0.11–0.91% had a two-phase structure, while the alloy with a carbon deficit of 1.31% contained inclusions of the η phase in addition to WC and γ phase. It is established that the retardation of the growth of tungsten carbide grains is observed with a decrease in the carbon content during liquid-phase sintering. The concentration of dissolved tungsten is established by electron probe microanalysis. It was 10, 12, 15, and 19 wt % for carbides with a normal, low, mid, and high carbon deficit, respectively. The use of narrow-fraction tungsten carbide powders makes it possible to fabricate carbides with rounded grains having a shape factor of about 0.77. The alloy with a carbon deficit of 0.91% relative to the stoichiometric ratio had the best combination of hardness and crack resistance:11.1 GPa and 16.0 mPa m1/2.

About the authors

E. N. Avdeenko

National University of Science and Technology “MISiS”

Author for correspondence.
Email: avdeenko.misis@mail.ru
Russian Federation, Moscow, 119049

E. I. Zamulaeva

National University of Science and Technology “MISiS”

Author for correspondence.
Email: zaumaleva@gmail.com
Russian Federation, Moscow, 119049

A. A. Zaitsev

National University of Science and Technology “MISiS”

Author for correspondence.
Email: aazaitsev@bk.ru
Russian Federation, Moscow, 119049

I. Yu. Konyashin

National University of Science and Technology “MISiS”

Author for correspondence.
Email: konyashini@gmail.com
Russian Federation, Moscow, 119049

E. A. Levashov

National University of Science and Technology “MISiS”

Author for correspondence.
Email: levashov@shs.misis.ru
Russian Federation, Moscow, 119049

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