基于化学法途径的板状超粗晶硬质合金制备及其腐蚀磨损行为研究

Ultra-coarse grained WC–Co cemented carbides are widely used in rock drilling and engineering construction, and their service lives are determined by hardness and fracture toughness. In the case of this grade WC–Co cemented carbide, therefore, it has become a hot research area to obtain platelet-like WC grains which offer characteristics of both high hardness and toughness. Due to the homogeneity and degree of platelet-like WC grains can’t be guaranteed using reaction sintering method and recrystallization method, this project presents a novel route to fabricate ultra-coarse grained WC–Co cemented carbide with platelet-like WC grains. Firstly, medium platelet-like WC particles are synthesized through the molten salt method coupling with mechanical activation method. Consequently, WC–Co cemented carbide with the homogeneous platelet-like WC grains is obtained by chemical route. Moreover, this project focuses on investigating the formation mechanism of platelet-like WC particles during synthesis, exploring the controllable regularity of the morphologies of WC particles, and constructing the relationships among preparation, microstructure and mechanical properties of WC–Co cemented carbide. In addition, the influences of Ni、Cr on the corrosion wear of ultra-coarse grained WC–Co cemented carbides in different corrosion mediums are investigated, the combined effects of electrochemical corrosion and friction wear are analyzed. At last, the design guideline on microstructure and composition for ultra-coarse grained WC–Co cemented carbides with platelet-like WC grains in working situation would be proposed.

超粗晶硬质合金广泛应用在矿山开采和工程建设领域，其使用寿命受到硬度和断裂韧性的综合影响。因此，如何获得板状结构的WC晶粒，达到同时改善硬度和断裂韧性的目的，是超粗晶硬质合金研究领域的热点问题。本项目针对目前反应烧结法和再结晶法制备板状超粗晶硬质合金存在的WC晶粒尺寸不均匀、板状化程度不高等问题，提出一种新方法：采用机械活化耦合熔盐合成技术制备中颗粒级板状WC粉，再基于化学法途径获得板状超粗晶硬质合金。重点研究机械活化耦合熔盐合成板状WC颗粒的形成机理，揭示耦合反应过程中WC结构的调控机制，解析板状超粗晶硬质合金制备技术—结构—力学性能的内在关联；并深入开展板状超粗晶硬质合金在腐蚀介质中的腐蚀磨损行为研究，探明合金成分对电化学腐蚀及摩擦磨损之间联合效应的影响规律，进而为板状超粗晶硬质合金在实际工况条件下的结构与成分设计提供理论基础。

超粗晶硬质合金广泛应用在矿山开采和工程建设领域，其使用寿命受到硬度和断裂韧性的综合影响。基于WC晶粒各向异性的特性，开发和设计的板状硬质合金具有高硬度和高韧性的特点，因而成为了硬质合金领域的研究热点。本项目探寻了一种板状超粗晶硬质合金新的制备方法：基于机械活化耦合熔盐合成中颗粒级板状WC粉，再采用化学法途径获得板状超粗晶硬质合金。揭示了合成温度、球磨时间、熔盐种类和数量对WC颗粒微观结构和物相的演变规律，得出合成温度和熔盐数量是制备中颗粒级板状WC粉体的关键因素。并评价了Ni、Cr3C2引入对板状超粗晶硬质合金显微组织和性能的影响。同时结合电化学分析和磨粒磨损测试，得出3wt%Ni的添加可进一步改善WC-6Co板状超粗晶硬质合金的力学性能、耐腐蚀性能，从而WC-3Co-3Ni板状超粗晶硬质合金在酸性、中性和碱性溶液中都表现出最佳的耐腐蚀磨损性能，这为板状超粗晶硬质合金的成分优化提供了科学参考。