Cutting Tool Materials of Cubic Boron Nitride Single Crystal

单晶立方氮化硼在刀具的实际应用中有许多问题需要解决。1987年，记者团队在世界上首次成功地生长出了单晶立方氮化硼。高压高温条件下生长CBN比金刚石生长更困难。目前尚缺乏立方氮化硼晶体生长的基础数据。这项研究涵盖了CBN增长的基本数据。CBN不能在非等温条件下生长，稳定的P-T条件必须通过高压实验来确定。确定相边界曲线为P=T/200-3.5(Gpa，C)。研究发现，CBN在常压下稳定在700℃以下。生长晶体所用的BN溶剂选自碱和碱土氮化硼。通过高压实验确定了不同溶剂-BN体系合成CBN的P-T区。结果表明，在4-5 Gpa和100-1200℃的温度下合成了CBN，其最低合成温度与体系的最低液相线相吻合。然而，在1700℃或更高的温度下观察到CBN的生长。用金刚石和立方氮化硼的晶种进行了立方氮化硼晶体的生长。我们发现CBN薄膜可以在1200-1300℃范围内生长。这一新发现为刀具的应用提供了CBN生长的基础技术。

Single crystal cBN has many problem to solve for practical application of cutting tools. In 1987, the reporter's groupe has succeeded to growth single crystal cBN at first time in the world. High pressure high temperature of cBN growth is more difficult than the diamond growth. The basic data for the crystal growth of cBN are lacked. This study covers basic data for cBN growth. cBN cannot grow at non-equiriblium condition, then the stable P-T condition of cBN must be determined by high pressure experiments. We determined phase boundary curve as P=T/200 - 3.5(Gpa, C). It was found that cBN is stable to 700 C at normal pressure.BN solvents for the crystal growth were selected from alkali and alkali-earth boronnitride. cBN synthesized P-T regions were determined for various solvents-BN systems by high pressure experiments. We found that cBN was synthesized above 4-5 GPa and 100-1200 C. The minimum temperature of cBN synthesis coincides the minimum liquidus line of the system. Growth of cBN, however, was observed at 1700 C or higher temperature. Crystal growth of cBN was carried out using seed crystals of diamond and cBN. We found that cBN film can be grow at 1200-1300 C region. This new finding provides basic technology of cBN grow for the application of cutting tools.