WC-Co cemented carbides, known for their exceptional mechanical strength, wear resistance, and toughness, have gained significant importance in various industries, leading to a steady rise in their demand and production. The scarcity of raw materials and the complexities involved in their extraction have pro‎mp‎ted a global initiative towards recycling these materials since their inception. Countries like Japan had notably utilized secondary sources for their production. This study introduced a method for recycling WC-Co carbide waste, particularly from used cutting tools, which was divided into two main phases. The initial phase examined the dry oxidation of these carbides for two pivotal reasons. Firstly, high-temperature oxidation significantly shortened their service life by deteriorating their mechanical properties, a critical factor since oxidation was a key step in numerous recycling processes. The inherent difficulty in crushing and reprocessing these high-strength materials into powder form was initially addressed by oxidizing the waste at high temperatures. This process substantially weakened the materials, thereby simplifying the powder production process. Essentially, the waste was first subjected to high-temperature oxidation and then ground into a fine powder (less than 40 microns) using a ball mill. Subsequently, this powder was chemically restored to its original composition through treatment with natural gas, making it suitable for re-sintering into the primary product. Future research would delve into the high-temperature oxidation of tungsten-cobalt cemented carbides through the use of response surface methodology and full factorial design for experimental design. Practical analyses, including XRD and SEM/EDS, were employed for phase analysis and to investigate the oxide structures. Additionally, a feedforward neural network was utilized to model and predict the high-temperature oxidation behavior of these materials. In the latter part of the thesis, the feasibility of regenerating and synthesizing these materials in-situ using natural gas for their recycling was explored through practical experiments. This segment involved the analysis of the final powder using XRD phase analysis and FESEM microscopy. The findings revealed that among the factors of temperature, airflow, duration, and their interactions, temperature and its square significantly influenced the outcome, accounting for 85% of the overall effect of influential factors, establishing temperature as the most crucial element in their dry oxidation process. Additionally, airflow was identified as vital for mitigating the loss of mass due to the sublimation of tungsten oxide at elevated temperatures. The optimal conditions for the high-temperature oxidation of these cemented carbides were determined to be within the temperature range of 900 to 1000 degrees Celsius, accompanied by a direct airflow. Furthermore, the experiments demonstrated successful regeneration and synthesis of the powders at temperatures of 850, 900, and 1000 degrees Celsius under a flow of natural gas. Notably, the sample treated at 1000 degrees Celsius exhibited the lowest structural porosity, with a porosity value of 19.5%, indicating densely packed powder particles. Unlike many other recycling methods, the final structure did not contain any intermediate or semi-stable phases. Overall, this method involves fewer steps compared to other recycling techniques, such as those involving hydrometallurgy or molten zinc baths, and can be simpler.

مهدي علي زاده

بهزاد صادقيان

عبدالمجيد اسلامي , مهدي احمديان