Efficient oxidation of scrap WC-8Co cemented carbide by microwave roasting

Oxidation is crucial for recovering W and Co from scrap cemented carbides. To intensify this process, microwave roasting was employed in this study for efficient oxidation of one of the main carbides, namely scrap WC-8Co cemented carbide. The oxidation performance of the carbide in the temperature range from 300 °C to 800 °C was explored based on the thermodynamic and electromagnetic analyses. The microwave penetration depth, D p , of scrap WC-8Co cemented carbide was found to be only 21.14 mm, indicating its good microwave absorption capability. As the temperature increased from 300 °C to 700 °C, the mass gain, oxidation efficiency, and decarburization percentage increased from 0.48 %, 83.73 %, and 3.35 % to 18.74 %, 98.95 %, and 98.26 %, respectively. Meanwhile, the carbon content in the carbide decreased from 5.49 wt% to 0.099 wt%. Increasing the temperature to 800 °C had little effect on oxidation. The major phases, including WC, Co, and CoO, were ultimately oxidized to WO 3 and CoWO 4 , accompanied by unit cell expansion and crack formation. Compared to conventional roasting, microwave roasting at the optimal temperature of 700 °C resulted in a 4.75-fold reduction in residual carbon content. These findings demonstrated the advantage of oxidation of scrap WC-8Co cemented carbide through low-temperature microwave roasting.