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http://dx.doi.org/10.7844/kirr.2022.31.4.19

Preparation and Characterization of Tungsten Carbide Using Products of Hard Metal Sludge Recycling Process  

Kwon, Hanjung (Division of Advanced Materials Engineering, College of Engineering, Jeonbuk National University)
Shin, Jung-Min (BestR, ETECHHIVE)
Publication Information
Resources Recycling / v.31, no.4, 2022 , pp. 19-25 More about this Journal
Abstract
In this study, tungsten carbide (WC) powder was prepared using a novel recycling process for hard metal sludge that does not use ammonium paratungstate. Instead of ammonia, acid was used to remove the sodium and crystallized tungstate, resulting in the formation of tungstic acid (H2WO4). The WC powder was successfully synthesized by the carbothermal reduction of tungstic acid through H2O decomposition, reduction of WO3 to W, and formation of WC. The carbon content and holding time at the carbothermal reduction temperature were optimized to remove free carbon from the WC powder. As a result, most of the free carbon in the WC powder prepared from sludge was removed, and the content of free carbon in the synthesized WC powder was lower than that in commercial WC powder. Moreover, the crystallite size of WC prepared from H2WO4 was much smaller than that of commercial micron-sized WC powder produced from APT. The small crystallite size of WC induces grain growth during the sintering of the WC-Co composite; thus, a WC-Co composite with large WC grains was fabricated using the WC powder prepared from H2WO4. The large WC grains affected the mechanical properties of the WC-Co composite. Further, due to the large grain size, the WC-Co composite fabricated from H2WO4 exhibited a higher toughness than that of the WC-Co composite prepared from commercial WC powder.
Keywords
hard metal; sludge; recycling; tungsten carbide; sintering;
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