Thermo-Chemical Wear Mechanism of Diamond as a Tool Material

在超精密切削中，由于切削刃与被切削材料的摩擦接触不可避免地要承受高温，因此热化学过程被认为是金刚石切削刃磨损的一个重要机理。为了解其磨损机理，进行了模拟切削刃磨损过程的简化试验。从热力学和量子化学的角度分析了金刚石与金属之间的化学反应行为。实验和分析结果表明，在金刚石既能氧化金属又能还原金属氧化物的条件下，金刚石与金属接触表面在加热时发生氧化热化学磨损。金刚石的磨损也是由于接触金属的碳化或金刚石表面的碳原子向金属中扩散而引起的。在此基础上，预测了金刚石发生热化学磨损的温度和氧分压条件。虽然由于受到实际环境条件的限制，很难防止切削刃的磨损，但热化学工艺的应用似乎有助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. Analyses on the behavior of chemical reaction between diamond and metal are also made based on the thermodynamics and quantum chemistry. The results of the experiments and analyses show that the thermo-chemical wear by oxidation on the diamond surface contacting with a metal is observed when it is heated under the condition that the metal can be oxidized and also the metal oxide can be deoxidized by diamond. The wear of diamond is also promoted by carbonization of the contacting metal or the diffusion of carbon atoms on diamond surface into the metal. Based on the analyses, the condition on temperature and oxygen partial pressure under which the diamond shows thermochemical wear can be predicted. Although it is difficult to prevent the wear of cutting edge due to the restriction in realistic condition of atmosphere attainable, the application of thermo-chemical process seems to be useful for the high efficiency polishing of diamond.