Study on Termo-Chemical Wear Mechanism of Diamond and Its Application to High Efficiency Polishing

热化学过程被认为是超精密金属切削中金刚石刃口磨损的基本机理，因为与被加工材料摩擦接触的刃口不可避免地会受到高温的影响。为了解其磨损机理，进行了模拟刀具刃口磨损过程的简化实验。在热力学和第一性原理量子计算的基础上，分析了金刚石与金属的化学反应行为。实验和分析结果表明，在金属可以氧化的温度下加热时，金刚石表面与金属接触时的热化学氧化磨损是主要过程，金属氧化物也可以被金刚石还原。金刚石的磨损也是接触金属的加速碳化或金刚石表面的碳原子扩散到金属中。利用热力学分析，可以预测金刚石发生化学磨损的温度和氧分压条件。根据第一原理计算，可以很好地理解金刚石氧化和碳化的磨损过程。在可获得逼真气氛的条件下，金刚石工具的磨损控制似乎比较困难。然而，热化学工艺的应用似乎有利于金刚石的高效抛光。

Thermo-chemical process is considered to be an essential mechanism of wear of diamond cutting edge in ultraprecision metal cutting, because the cutting edge under attritious contact with workmaterial is inevitably subject to elevated temperature. To understand the wear mechanism, the simplified experiments simulating the wear process of cutting edge are carried out. Analyzes on the behavior of chemical reaction between diamond and metal are also made based on the thermodynamics and first principal quantum calculation. The results of the experiments and analyzes show that the thermo-chemical wear by oxidation on the diamond surface contacting with a metal is predominant process when it is heated under the temperature that the metal can be oxidized and also the metal oxide can be deoxidized by diamond. The wear of diamond is also accelerated carbonization of the contacting metal or the diffusion of carbon atoms on diamond surface into the metal. Using the termodynamics analyzes, the conditions on temperature and oxygen partial pressure under which the diamond shows termo-chemical wear can be predicted. Based on the first principal calculation, the wear processes of diamond due to oxidation and carbonization can be well understood. The wear control of diamond tool seems to be difficult under the condition of realistic atmosphere attainable. However, the application of thermo-chemical process seems to be useful for the high efficiency polishing of diamond.