The Introduction of Super-Hard Cutting Tool Materials
The super-hard material is diamond and CBN which hardness is several times than other materials.Diamond is the hardest substance in the nature ,but CBN’s hardness is only lower than it .In recent year ,the super-hard materials have been developed rapidly .
The diamond cutting tool material is divided into 5 categories.
1) Natural Diamond
2) Synthetic polycrystalline diamond(PCD) take graphite as raw material and produced with high temperature and pressure .
3) PCD/CC is formed with PCD coating with thckness0.5mm onto the tungsten carbide substrate .
4) CD:to coating a film with thickness10~25um onto the cutting tools by means of CVD
5) TFD:To coat a film with thickness over 0.2mm onto another substrate with CVD ,meanwhile cut it in some sizes and then weld them onto the carbide inserts
The ND crystalline anisotropy ,the grinding direction must be considered in sharpening process,however the PCD with crystalline isotropy ,its hardness is lower than ND ,but toughness and T.R.S is higher than it .
The diamond cutting tools are very good at processing non-iron metals and non-metallic materials such copper, aluminum etc nonferrous metals and its alloys ,porcelain, tungsten carbide ,various fiber and particulate-strengthen composite materials ,plastic,rubber,.graphite,glass and wood. However it is incapable to process steel,iron and other ferrous metals .
The TFD has very good comprehensive performance with combination the merits of natural diamond and synthetic diamond,which bond with base solidly ,and facilitate re-grinding several time ,so has very good application value and development prospect .
The producing process of CBN is same as PCD and PCD/CC,which is produced with the hexagonal boron nitride as raw materials and taking high temperature and pressure .The CBN is mainly used for process harden steel ,high-hardness cast iron and other hard metals and nonmetallic materials .If use the tungsten carbide or ceramic cutting tools to cut some hard and fragile materials ,the tools’ service life is very short or even completely incapable to do the work ,however it is very easy to do that if use the super-hard materials which is solely capable to take high-precision cutting on the nonferrous materials . 
