MgO与Li2O摩尔比及烧结温度对结合剂及cBN磨具性能的影响

以ZnO-Na₂O-SiO₂-Al₂O₃-B₂O₃陶瓷体系为基础, 制备了添加不同摩尔比Li₂O和MgO的陶瓷结合剂及立方氮化硼(cBN)磨具。利用X衍射测试仪、线性热膨胀测试仪、扫描电镜等研究了MgO∶Li₂O摩尔比( M 值)和烧结温度对陶瓷结合剂及磨具性能的影响。结果表明: 随着 M 值增加, 结合剂的软化点温度增加, 耐火度及化学稳定性均增强, 线性热膨胀系数先增加后降低。当 M 值为0.67时, 随着烧结温度的升高, 石英晶相的析出被抑制, 诱导析出Mg(Zn)Al₂O₄晶相, 且含量逐渐增加, 尺寸先减小后增加; 当温度为870 ℃时, Mg(Zn)-Al₂O₄晶粒尺寸最小, 约为2 μm, 结合剂结构最为致密, 抗折强度达到最大值136.28 MPa。随着烧结温度的提高, cBN磨具气孔率和吸水率先降低后增加, 体积密度、硬度、抗折强度、磨耗比以及磨削效率先增加后降低; 当烧结温度为890 ℃, 磨耗比及磨削效率最高, 分别为98.72%和1.3675 g·min^-1。

Effect of MgO:Li2O molar ratio and sintering temperature on properties of vitrified bond and cBN grinding wheel

The vitrified bonds with different molar ratios about MgO∶Li2O( M ) and cBN wheels were prepared at the base of ZnO-Na2O-SiO2-Al2O3-B2O3 ceramic system. X-diffraction analysis, SEM and thermal expansion coefficient tests were used to study the influence of M and sintering temperature on the properties of vitrified bonds and cBN wheels.The results show that with the M value increasing, the soften temperature, refractoriness and chemical stability of the bond increase, while the thermal expansion coefficient increases and then decreases. When the M value is 0.67, the increasing of the temperature restrains the quartz crystal separating. Meanwhile, the content of Mg(Zn)Al2O4 crystalline phase increases, and the size decreases at first and then increases. Moreover, when the temperature reaches 870 ℃, the grain size is the minimum about 2 μm, and the most compact microstructure is obtained. At the same time, the bending strength of the bond reaches the maximum value of 136.28 MPa. As the sintering temperature increasing, the porosity and water absorption of cBN wheel decrease at the beginning and then increase. However, its bulk density, hardness, bending strength, abrasion and grinding efficiency exhibit contrary trend. When the temperature is 890 ℃, the abrasion and grinding efficiency reache the maximum values of 98.72% and 1.3675 g·min-1 respectively.