基于单脉冲放电的微细电火花磨削聚晶立方氮化硼的研究

Research on Micro-size Electrical Discharge Grinding of Polycrystalline Cubic Boron Nitride Based on Single Pulse

聚晶立方氮化硼(PcBN)是一种具有较高的硬度、较高的耐磨性和良好的化学稳定性的高温高压合成材料,其符合现代先进切削技术“高效率、高精度、柔性、绿色”的基本特点,被广泛应用于黑色金属切削加工工具领域。电火花放电磨削是加工聚晶立方氮化硼刀具有效的方法之一,特别适合于加工复杂形状和薄刃PcBN刀具。单脉冲放电磨削是研究电火花放电磨削加工机理的基础之一,是研究微尺度放电磨削的有效方法。文章在自主研发的单脉冲放电电源装置上开展试验,选择2μm粒度、90%cBN含量的PcBN复合片作为被加工材料,研究了单脉冲放电腐蚀坑的形貌及放电参数与材料去除率的关系,如腐蚀坑半径、腐蚀坑深度和深径比等。实验结果表明:随着脉冲持续时间的延长,放电腐蚀坑的半径和热影响面积先是快速增加,然后缓慢增加,最后趋于稳定;腐蚀深度一般在0.2~0.5μm范围内平缓变化,脉冲持续时间对放电腐蚀坑深度没有明显影响。随着脉冲持续时间的延长,腐蚀坑半径与深度之比在13~20范围内发生变化,基本呈现下降趋势。

Polycrystalline cubic boron nitride(PcBN) is a high temperature and high pressure composite material with high wear resistance and good chemical stability. It is consistent with the basic characteristics of modern advanced cutting technology of "high efficiency, high precision, high efficiency and green". Currently, it is widely used in the field of ferrous metal cutting tools. Electrical discharge grinding is one of the most effective methods for machining of polycrystalline cubic boron nitride cutters. It is especially suitable for machining of complex shapes and thin edge cutters. Single pulse electrical discharge grinding is the basis of continuous EDG machining and an effective method to study the micro-scale electrical discharge grinding. In this paper, the morphology of single pulse discharge corrosion pits and the relationship between discharge parameters and material removal rate, such as the deep-diameter ratio of the corrosion pits, the pulse width and the deep-diameter relationship of the corrosion pits, are studied with the polycrystalline cubic boron nitride composite sheet of 2 micron particle size as the test material. The experimental result shows that the radius and heat affected area of the discharge corrosion pit increases rapidly at first, then increases slowly, and finally keeps to stabilize with the extension of pulse duration. The corrosion depth generally varies gently in the range of 0.2-0.5 micron meters, and the pulse duration has no obvious effect on the depth of discharge corrosion pit. With the extension of pulse duration, the ratio of radius to the corrosion pit depth changes in the range of 13-20, and the ratio basically declines.