WC-Co硬质合金最新进展

Latest Development of WC-Co Cemented Carbide

硬质合金是一种具有独特性能组合的材料,传统硬质合金的硬度与韧性是一对此消彼长矛盾体。随着硬质合金在相关产业应用的不断发展,对其性能的要求越来越高,故开发出同时具有高硬度和高韧性的新型硬质合金显得非常重要。综述了超细及纳米晶粒硬质合金、粗晶硬质合金、板状晶粒增强硬质合金、双相或混合结构硬质合金和功能梯度硬质合金5种在国内外实现了高硬度、高耐磨性与高韧性协调统一的新型硬质合金。由于硬质合金是利用粉末冶金技术制备的金属陶瓷复合材料,所以粉末原料的尺寸、形状以及烧结方式对所得到的产品的性能有非常重要的影响。分析了晶粒大小、微观结构、原料性能等对硬质合金硬度、耐磨性、韧性等宏观力学性能的影响,并对相关的强化机制进行阐述。这些新型硬质合金中,粗晶粒硬质合金常用于要求良好韧性的应用中;梯度微观结构硬质合金可用于定制性能,随着相关技术的发展将进一步开发其应用;虽然目前能制备出纳米粉末,但是烧结出真正的纳米微观结构仍存在问题;关于开发特殊粉末(如纳米粉末结构,板状晶体)和特殊微观结构(如双相硬质合金)都需更进一步的研究。

Cemented tungsten carbides are a special class of materials that exhibit a unique combination of properties, and the hard- ness and the toughness of conventional cemented carbides were a pair of counter-balance contradiction. With the increasing develop- ment of the application of cemented carbide in related industry, the demand on properties was higher and higher, therefore, the devel- opment of new cemented carbide with high hardness and high toughness was very important. A total of five kinds of cemented carbides, i. e. , uhrafine and nano-grain cemented carbide, coarse grain cemented carbide, cemented carbide with plate-like WC grains, double cemented carbide, functionally gradient cemented carbide, were introduced in detail. Hard-metals were commercially metal-ceramic composites produced by powder metallurgy technology, so the size and the shape of the powder, as well as the way of sintering, had very important influences on the properties of products. The grain size, microstructure and material properties that affected the macro- scopic mechanical properties such as hardness, wear resistance and strength toughness were investigated, and the strengthening mecha- nism was expounded. Among these new types of cemented carbides, coarse grain cemented carbide was often used in applications re- quiring high toughness ; the gradient microstructure carbide was used to tailor properties, and these developments would find additional applications for hardmetals ; powder particles of nano-size could be produced, but the formation of real nano-microstructure by sintering remained a challenge ; the exploitation of unique powders （ such as nano-powders and platelets ） and unique microstructure （ such as double cemented carbide） required further innovation consciousness.