Preparation of high-purity and ultrafine WC-Co composite powder by a simple two-step process

• Published in: Advanced powder technology : the international journal of the Society of Powder Technology, Japan Japan, 2020-05, Vol.31 (5), p.1940-1945
• Main Authors: Wang, Kai-Fei, Chou, Kuo-Chih, Zhang, Guo-Hua
• Format: Article
• Language: English
• Subjects: Carbothermic reduction; Free carbon; Particle size; WC-Co composite powder
• ISSN: 0921-8831; 1568-5527
• DOI: 10.1016/j.apt.2020.02.027

[Display omitted] •A new method is proposed to prepare high-purity and ultrafine WC-Co powder.•WC-Co powder with a size of 160–410 nm is prepared when the C/WO2.9 ratio is 2.3–2.7.•A lower C/WO2.9 ratio and higher temperature can decrease free carbon content.•WC-Co powder with different sizes can be prepared by adjusting C/WO2.9 ratio and temperature. In this study, high-purity and ultrafine WC-6%Co composite crystallites was synthesized by a simple two-step process consisting of the precursor-formation of the mixture of blue tungsten oxide (WO2.9) and cobaltic oxide (Co2O3) and the following deep reduction and carburization with CH4-H2 mixed gases. The experimental results revealed that after the first carbothermic reduction stage at 1050 or 1150 °C, a mixture of W, WO2 and Co7W6 was obtained, which was further carburized to the WC and Co phases by CH4-H2 mixed gases at 900 °C. With the increase of C/WO2.9 molar ratio, the particle sizes of first-stage precursor and carbonized product were both decreased. The particle sizes of final products are mainly determined by C/WO2.9 ratio and reaction temperature at the first stage. When the C/WO2.9 ratio was in the range of 2.3–2.7, the high-purity WC-6%Co composite powder with the average particle sizes of 160–410 nm could be obtained.