VC和碳含量对超细晶硬质合金室温和高温性能的影响

以原位还原碳化技术制备的WC-8Co复合粉和VC粉末为原料,采用低压烧结技术制备出超细晶硬质合金。系统研究了VC添加量和复合粉中碳含量对硬质合金的相组成、显微组织、室温和高温力学性能的影响。结果表明:硬质合金的晶粒尺寸、硬度和断裂韧性主要受VC添加量的影响,且随VC添加量的增加呈单调变化;抗弯强度随VC添加量的变化趋势与碳含量有关;压缩强度随温度的变化呈现先降低后升高的趋势;当WC-Co复合粉的碳含量为5.60%～5.68%(质量分数)、VC添加量不超过0.5%时,可分别制备出室温抗弯强度为4482MPa和600℃下抗压缩强度为4914MPa的高综合性能的超细晶硬质合金。基于微观组织特征的分析,结合弹-塑性有限元模型对应力分布的模拟,对超细晶硬质合金力学性能的变化规律及影响机理进行了分析。

Effect of VC addition and carbon content on mechanical properties of ultrafine cemented carbides at room and high temperatures

Using VC and WC-8Co composite powder, prepared by in-situ reduction carbonization, as raw materials, ultrafine WC-Co cemented carbide was prepared by sinter-HIP technology. The influences of the contents of the VC addition and the carbon of the composite powder on the phase composition, microstructure, and mechanical properties of the cemented carbides were investigated. The results showed that the grain size, hardness and fracture toughness of cemented carbides were mainly affected by the content of VC addition. These properties changed monotonically with the increase of VC content. The change of transverse rupture strength with VC content was related to carbon content. The compression strength decreased first and then increased with the increase of temperature. With the optimized carbon content of WC-8Co composite powder in the range of 5.60-5.68wt.% and the VC addition no more than 0.5wt.%, the high comprehensive performance ultrafine cemented carbides were prepared, with the highest value of TRS at room temperature and compression strength at 600oC as 4482MPa and 4914MPa, respectively. Based on the characteristics of the microstructure and the stress distribution, simulated by the elastic-plastic finite element model, the law of performance change and the mechanism of its performance were analyzed.