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| In situ synthesis of nanoscale NbC-Co composite powder and its application in
sintered cemented carbides |
| WANG Haibin1，ZHANWangbin1，LIU Xuemei1，LIU Chao2，
HOU Chao1，SONG Xiaoyan1 |
| 1College of Materials Science and Engineering，Key Laboratory of Advanced Functional Materials，Education
Ministry of China，Beijing University of Technology，Beijing 100124，China；2Xiamen Tungsten Co.，Ltd.，
Xiamen 361009，China |
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Abstract The optimum synthesis process of nanoscale NbC-Co composite powder by in situ reactions of Nb2O5，
Co and carbon black was investigated in the present work. Then the obtained composite powder was used as an additive
of WC-Co to prepare cemented carbide bulk material by HIP-sintering. The effects of the additive on the microstructure
and property of the WC-Co cemented carbide were studied. By means of thermodynamic calculations
and in situ reaction experiments，it shows that the transition of Nb2O5 in the reactions with carbon black proceeds
in the sequence of Nb2O5→NbO2→NbC. The addition of Co，not only decreases the reaction temperature，but also
results in simultaneous occurrence of reduction and carburization reactions which normally take place in two steps.
After the optimization of the carbon content and reaction temperature，the synthesized NbC-Co composite powder
has no impurity phases，a low oxygen content and a mean particle size is 82 nm. The addition of nanoscale NbCCo
lead to a decrease in grain size from 0.70 μm to 0.48 μm and a more homogeneous microstructure in the prepared
WC-Co cemented carbide. Moreover，the hardness of the cemented carbide is significantly enhanced at both
room and high temperatures due to the addition of nanoscale NbC-Co. Particularly at 800 oC，the WC-12Co-1NbC
cemented carbide still maintaines a hardness of 890HV30.
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Received: 29 April 2020
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2021, Vol. 31 
