纳米晶WC-Co硬质合金中WC晶粒度的定量测量

Quantitative measure of WC grain size in nanocrystalline WC-Co hardmetal

通过改进金相样品的制备方法,将纳米晶WC10Co硬质合金在场发射扫描电镜10万倍放大倍率下可获得衬度良好、WC晶粒轮廓清晰的二次电子像。采用截距法定量测量了合金中WC晶粒尺寸,结果表明:WC晶粒尺寸分布范围为12～109nm,平均晶粒尺寸45nm,对应的三维WC平均晶粒度为70nm。根据合金中WC在低角度(2θ≤50°)的(001)WC,(100)WC和(101)WC晶面衍射峰数据,用X射线衍射Scherrer公式测定的WC晶粒度的统计平均值为91nm,与定量金相分析结果接近并且都进入了纳米尺度范畴。实验还比较了WC晶粒的统计数量和人为因素对评估数据的影响。

Nanocrystalline WC-10Co hardmetal can be made by doping a new invented VC-based multi-grain-growth-inhibitor and suitable technical processing. The specification for quantitative measuring the grain size of WC in the alloy was explored. Under modified metallographic sample making and Murakami etching condition, the 100000 multiple magnified second electron(SE) images with good contrast and clear profile of WC grain for the alloy can be obtained by FESEM. The linear interception (LI) method was used to quantitatively measure the interception of WC grain in the collected SE images. The results show that the distribution of WC grain size is 12109nm; the average interception of WC grains is 45nm and the corresponding 3D mean grain size of WC is 70nm. In another way, the grain size of WC was determined by XRD Scherer formulation for (001)_(WC), (100)_(WC) and (101)_(WC) peaks at low brag angles(2θ≤50°). The calculated average value is 91nm, which is agreeable with measured 3D grain size of WC and can be auribed to nano scale. The effects of counted grain numbers and human factor on the statistic data are also investigated and discussed.