硬质合金电化学腐蚀行为的研究进展

硬质合金广泛应用于工业生产中,其服役环境复杂,除了要求其优异的力学性能之外,对其耐腐蚀性也提出了很高的的要求,因此,本文分析了国内外有关硬质合金腐蚀行为的研究及其进展。重点总结了实验室中常用的硬质合金腐蚀性能评价与表征方法,包括浸出法和电化学测试方法;从WC的平均晶粒尺寸、粘结相的种类和含量、溶液pH值、溶液中的阴离子、温度、W在Co中的固溶度(磁饱和强度)和合金元素(Cr、V、Ti、Ta、Ru、Al等)等方面分析了微观结构和服役环境对硬质合金腐蚀性能的影响;从腐蚀热力学与动力学两方面阐述了硬质合金的腐蚀机理。服役条件下硬质合金往往不是受到单一的电化学腐蚀作用,而是其它因素(静载荷、冲击载荷、摩擦等)与电化学腐蚀的联合作用,今后有必要开展这方面的研究;另外以往的研究者多从整体、统计的角度来评价硬质合金的电化学腐蚀行为,今后应该借助更加先进的电化学研究手段(如:电化学扫描探针显微镜、电化学隧道扫描显微镜等)进行微区电化学研究,在一个试样上同时研究粘结相和硬质相的电化学特性,这有利于说明硬质合金腐蚀的本质。

Research Progress on Electrochemical Corrosion Behaviour of Cemented Carbide

Cemented carbides are widely used in industrial production, but their service environments are really com- plicated, not only excellent mechanical properties are required, but also high corrosion resistance which plays an extremely important role during their service. Thus, this paper focuses on the recent studies and progress of the corrosion behaviours of cemented carbides, both at home and aboard. The methods of evaluation and characterization for the corrosion proper- ties of cemented carbides mainly used in laboratory, including immersion test and electrochemical investigation, were summerized. The influences of microstructure and service environments on corrosion behaviours of cemented carbides were analyzed from some specific factors, such as the average grain size of WC, kind and content of metallic binder, pH value and specific ions of electrolyte solution, temperature, solid solubility of W in Co （magnetic saturation）, and alloying element （Cr, V, Ti, Ta, Ru, and AI）, and so on. The corrosion mechanism of cemented carbides was discussed from thermody- namics and kinetics. In fact, the electrochemical corrosion is not the only factor which influences the service life, but to- gether with some other factors, for instance, the static load, impulsive load and wear. These factors should be and will be the focus in the future research. Previous studies were mainly from monolithic and statistical angles. To better reveal the essence of corrosion, the following investigations shoud be centred on the study of the electrochemical properties of the binder and that of the carbides at the same time in an micro region of one sample with the help of more advanced ECSPM, ECSTM, and others.