PAN Feng¹，SHANG Huijun²，LI Hengli³，DU Zhan⁴

1. State Key Laboratory of Mesoscience and Engineering， Institute of Process Engineering， Chinese Academy of Sciences，Beijing 100190， China；2. College of Materials Science and Engineering， Beijing University of Technology， Beijing 100124， China；3. School of Chemistry and Chemical Engineering， Shihezi University， Shihezi 832003， China；4. Chinalco Environmental Protection and Energy Conservation Group Co. ， Ltd. ， Xiong’an 050004， China

Abstract

Significance Using nano or ultra-fine tungsten carbide cobalt （WC-Co） powder as thermal spray material can effectively solve the wear and corrosion problems in mechanical parts. This paper summarizes and analyzes the research progress on enhancing the preparation process of such powders.

Progress Based on various enhancement methods and approaches， different preparation methods of nano or ultra-fine WC-Co powder are reviewed， and their reaction paths are analyzed. The role of cobalt （Co） in the preparation process of nano or ultrafine WC-Co powder is also discussed. Enhancement technologies for the preparation process mainly include mechanical force enhancement， atomic or molecular-level enhancement， and gas-phase carbon source enhancement. The reaction paths during the preparation process mainly involves two stages： reduction and carbonization. There are three paths：（1） tungsten carbide （WC） and η-phase are formed during carbonization；（2） tungsten trioxide （WO₃） is first reduced to tungsten （W）， then the η-phase is formed， followed by further carbonization to form WC-Co；（3） the reduction and carbonization process occurs without the formation of the η-phase. During the preparation of nano or ultra-fine WC-Co powder， Co plays the roles of catalysis， promoting carbonization， reducing the carbonization temperature， and decreasing the particle size of the product.

Conclusions and Prospects The preparation and application of nano or ultra-fine WC-Co powder can be further developed in the following areas. The mechanisms of the enhancement process in WC-Co powder preparation and the interaction mechanisms of Co-W-C should be further elucidated. The role of carbon-deficient η-phase in the preparation process remains unclear， and its impact on the diffusion mechanisms of W， Co， and C during preparation needs further analysis. By clarifying these mechanisms， the optimization of the preparation process can be guided， allowing for the control of the free carbon mass content within 0. 2%， and the production of composite powder with particle sizes under 100 nm. Moreover， the heat and mass transfer laws during the reaction process should be further examined. Using fluid simulation software， the heat and mass transfer processes between carbonized gas and solid raw materials in the reaction process can be simulated and analyzed， providing a basis for studying the reaction process mechanisms， optimizing the preparation process， and designing scalable reactors. The thermal spraying properties of composite powders also need to be further studied. It is necessary to apply the ultra-fine WC-Co powder prepared by relevant technical routes to the surface treatment of mechanical parts， testing the wear and corrosion resistance of the resulting coating， and using this performance data to refine the preparation process.