钴铁镍复合黏结相超细硬质合金显微组织与性能

Microscopic structure and properties of ultrafine cemented carbide with cobalt-iron-nickel composite binder

钴作为硬质合金应用最广泛的黏结剂,存在资源稀缺、成本高昂以及WC-Co硬质合金耐腐蚀性能较差等问题,综合考量生产成本与改善性能,本研究采用铁镍部分代替钴组成复合黏结剂,以其制备超细硬质合金,研究其显微组织和力学、耐蚀耐磨性能的关系。结果表明,黏结相中Fe/Ni质量分数比增加,使得合金WC晶粒细化和黏结相分布不均,合金的硬度和抗弯强度分别提高与降低。合金在中性NaCl溶液中的耐腐蚀性能评估采用极化曲线测试与浸泡实验,黏结相添加Ni能提高合金耐蚀性,归因于Ni的钝化特性与促进腐蚀产物膜的形成。硬质合金摩擦系数和磨损率与Fe/Ni质量比呈负相关,合金耐磨性的提高主要归因于黏结相的强度增强和WC晶粒细化合金硬度提高。

As the most widely used binder for cemented carbide, cobalt has some problems, such as resource scarcity, high cost, and WC-Co cemented carbide poor corrosion resistance. Considering the production costs and performance improvement, iron and nickel, instead of cobalt, were used to form a composite binder, with which ultrafine cemented carbide was prepared, and the relationships between its microscopic structure and mechanics as well as corrosion resistance and wear resistance were studied. The results show that the increase in Fe/Ni mass fraction ratio in the binder makes alloy WC grains refined and the distribution of binder uneven,and thus the hardness and anti-bending strength of alloys are increased and decreased, respectively. The corrosion resistance of alloys in neutral NaCl solutions was evaluated by polarization curve tests and immersion experiments. The addition of Ni to the binder improves the alloy corrosion resistance, which is attributed to the passivation characteristics of Ni and the formation of films promoting corrosion product. The friction coefficient and wear rate of cemented carbide are negatively correlated with Fe/Ni mass ratio. The improvement in alloy wear resistance is mainly due to the strength enhancement of binder phase and the hardness improvement of alloy caused by WC grain refinement.