WO3添加量对超粗硬质合金微观结构及性能影响*

Effect of WO3 content on microstructure and properties of ultracoarse grained cemented carbide

摘要:

本文以WC、WO₃、Co、C为原料,通过原位细晶溶解-析出长大法制备了超粗硬质合金,并分析了不同WO₃添加量对合金微观结构及性能影响规律。结果表明：初始粉末中加入的WO₃和C在烧结过程中将发生原位一步还原碳化反应转化为高活性的细WC,促进溶解-析出长大现象,使超粗硬质合金WC平均晶粒度随着WO₃含量增加而增大。同时,WO₃添加能够减少粗WC晶粒微观缺陷和曲边的阶梯状表面,平直化晶粒边界,使其形貌趋于形成完整的三角棱柱体,其(0 0 0 1)晶面占比高,能够有效提高合金硬度,阻碍裂纹扩展,增加钴相韧性断裂比例。当WO₃添加量为4.20wt.%时,制备的超粗硬质合金具有最大的硬度(1085kgf/mm₂⁾和抗弯强度(2692MPa)。

Abstract:

In this paper, ultracoarse grained cemented carbide was prepared by in-situ fine grain dissolution-precipitation method with WC, WO₃, Co and C as raw materials. The effects of different WO₃ content on the microstructure and mechanical properties of the alloy were analyzed. The results show that the WO₃ and C could undergo in-situ reduction-carbonization reaction to form fine WC with high activity. In the liquid phase sintering, fine WC dissolution-precipitation could promote the coarse WC grains growth, reducing the micro defects and growth steps, flattening the boundary of WC grains, which could make the morphology of coarse WC grains tend to a fully developed triangular prism. The ultracoarse WC grains with high flattening degree effectively increased the proportion of WC (0 0 0 1) axial plane, improved the hardness, hindered the crack propagation, and strengthened the alloy. So, the alloy with 4.20wt% WO₃ added had the maximum hardness (1085kg/mm2) and transverse rupture strength (2692MPa).