铁镍比与VC对WC-15%(Fe,Ni)细晶硬质合金组织与力学性能的影响

Effects of Fe/Ni Mass Ratio and VC Addition on Microstructure and Mechanical Properties of Fine Grained WC-15%(Fe,Ni) Cemented Carbide

利用OM、SEM、XRD进行微观组织与相组成分析,研究了铁镍比与VC对铁镍基硬质合金组织性能的影响规律。结果表明:添加质量分数0.5%的VC可显著提高合金硬度并细化组织,铁镍比越低,合金硬度提高幅度越大、组织细化效果越显著。当铁镍质量分数比为1∶5时,添加0.5%VC的合金硬度达91.5 HRA,WC平均晶粒度为0.6μm,相比于没有添加VC的合金,硬度增幅为4.7 HRA,WC晶粒尺寸降幅为2.4μm。当铁镍质量分数比小于1∶3时,VC的添加可提高合金抗弯强度,当铁镍质量分数比大于1∶3时,VC的添加反而降低合金抗弯强度。当合金中没有添加VC时,铁镍比的降低导致合金硬度下降,同时合金组织中的WC晶粒也明显粗化,这是由于WC在铁中的固溶度较小,铁含量的增加可有效抑制WC的溶解析出长大。当合金中添加VC时,铁镍比对合金硬度与晶粒度影响均较小,合金硬度均在91~92 HRA范围内,合金中WC平均晶粒度均为0.6μm。在合金抗弯强度方面,随着铁镍比的降低,有无添加VC的合金抗弯强度均整体呈先下降后上升的趋势,并分别在铁镍质量分数比1∶3与1∶2时达到峰值。综合来看,铁镍质量分数比1∶3,添加0.5%VC的合金具有最佳的综合性能,硬度达91HRA,抗弯强度达3590 MPa,晶粒度0.6μm。

The effects of Fe/Ni mass ratio and VC addition on the microstructure and mechanical properties of Fe-Ni based cemented carbide were researched via optical microscope, scanning electron microscopy and X-ray diffraction. The results show that the addition of 0.5%VC remarkably enhances the hardness and refines the microstructure of the cemented carbide, especially when Fe/Ni ratio is lower. The WC-15(Fe,Ni)-0.5 VC cemented carbide with Fe/Ni mass ratio of 1∶5 combines high hardness(91.5 HRA) and fine WC grain size(0.6 μm), which is 4.7 HRA higher and 2.4 μm smaller than that of the WC-15%(Fe,Ni) cemented carbide with the same Fe/Ni mass ratio but without addition of VC. The addition of VC can improve the bending strength of the cemented carbide with Fe/Ni mass ratio of below 1∶3, while the addition of VC will reduce the bending strength of the cemented carbide with Fe/Ni mass ratio of above 1∶3. The hardness of the WC-15%(Fe, Ni)cemented carbide without VC addition decreases and the WC grains grow up with the decreasing of Fe/Ni mass ratio, which are caused by the lower solid solubility of WC in Fe binder, so higher Fe content can promote the dissolution and precipitation process of WC. The WC-15%(Fe, Ni) cemented carbide with different Fe/Ni mass ratio and with addition of VC exhibits similar hardness within the range of 91~92 HRA and the same average WC grain size of 0.6 μm, which indicates that Fe/Ni mass ratio has little influence on the hardness and WC grain size of the cemented carbide. The bending strength of the WC-15%(Fe,Ni) cemented carbide with or without addition of VC firstly declines and then increases with the reduction of Fe/Ni ratio, and reaches the peak value at Fe/Ni mass ratio of 1∶3 and 1∶2, respectively. In general, the WC-15%(Fe,Ni)cemented carbide with Fe/Ni mass ratio of 1∶3 and the addition of 0.5%VC shows the best comprehensive properties, with hardness of 91 HRA, bending strength of 3 590 MPa and WC grain size of 0.6 μm.