VC和碳含量对超细晶硬质合金室温和高温性能的影响

Effect of VC Addition and Carbon Content on Mechanical Properties of Ultrafine Cemented Carbides at Room and High Temperatures

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。

Using VC and WC-8 Co 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 VC content and the carbon content of the composite powder on the phase composition, microstructure, and mechanical properties of the cemented carbides were investigated. The results show that the grain size, hardness and fracture toughness of cemented carbides are mainly affected by the VC content. These properties change monotonically with the increase of VC content. The change of transverse rupture strength with VC content is related to carbon content. The compression strength decreases first and then increases with the increase of temperature. With the optimized carbon content of WC-8 Co composite powder in the range of 5.60 wt%-5.68 wt% and the VC addition no more than 0.5 wt%, the ultrafine cemented carbides with high comprehensive performance were prepared. The highest value of TRS is 4482 MPa at room temperature, and compression strength is 4914 MPa at 600 ℃. 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.