Application and Prospect of diamond and ultra hard materials (2)
2015/9/3 13:45:25
3 points for attention in the application of diamond and hard materials
Natural single crystal diamond
In the current ultra precision machining, the cutting tool of the natural single crystal diamond is necessary. It can obtain a very sharp cutting edge, its edge radius can be achieved even scanning electron microscopy (SEM) can not detect the extent of. According to Igawa Naoya, a professor at Osaka University in Japan, the minimum amount of up to 2 ~ 4nm, which is the current highest level, is obtained by cutting the thickness of the chip 1nm. In 1986, Japan has established a special a diamond tip evaluation committee, to solve the problem of measuring tip, until today still have not been solved very well, just from 7.6nm increased to 2 ~ 4 nm. Asakai Akihito of Toshiba machinery in 1992 has proposed the use of scanning tunneling microscopy (STM) or atomic force microscopy (AFM) for the detection of the proposal, but did not report on the Chinese central China University of science and technology department in 1996 reported the use of AFM made progress, which is the achievement of joy.
The edge grinding of diamond cutting tools, although not a small achievement. But it is still a problem to be solved. The geometrical parameters of diamond cutting tools may be insufficient, so it is still to be explored so far. The average angle is 0 degrees, the angle is 6 to 5 degrees, and its end is two kinds, one is circular arc, the other is straight, the latter is sometimes called the edge, the length of which is selected according to the material to be processed. The circular arc lathe tool in cutting process is simple to adjust, but the adjustment of the flat blade is relatively time-consuming. If the application is in high precision machining of curved surface, the edge grinding of circular arc is very strict. According to the data show that the number of diamond production in Osaka, Japan, a few years ago to reach R + 0.05um, the UK is higher, reaching R + 0.02um.
In the process of cutting, the thermal conductivity of diamond is superior, the heat dissipation is quick, but it is better to pay attention to the cutting heat is not higher than 700, otherwise it will happen the graphite phenomenon, the tool will soon wear out. Because the diamond at high temperature and Ta, Ti, W, Zr, Ni, Co, Fe, Mn, Cr, Pt, etc..
Diamond sintered body (PCD)
The emergence of PCD in many ways to replace the natural single crystal diamond. Compared with natural diamond, the price of PCD is cheaper, and the edge grinding is far more convenient than that of natural diamond, so its application and popularization is especially rapid. In a large number of new materials, most of them are difficult to process materials, such as high silicon aluminum alloy, automotive engine piston large quantities of this material. In general, with a silicon content of less than 10% of aluminum alloy, with hard alloy cutting tools can be, but with more than 10% silicon content, you can only use PCD. High silicon aluminum alloy the silicon content was above 12%, and some have reached more than 18%, so PCD is.
However, due to the variety of PCD, there is a reasonable choice of the necessary. Its particle size, concentration, etc. will affect the hardness, wear resistance, etc.. Therefore, the application must be based on the type of material being processed. Hardness and other characteristics to consider reasonable parameters. Because of its isotropy, good wear resistance, processed into even better than that of single crystal diamond wire drawing die.
PCD production at home and abroad has been very popular, but the quality of a large difference, so the price is very large. In the domestic use of ultra fine grained GE blade, in the PneumoPreci ~ SMG325 sion ultra precision machine tool to do the cutting test, has reached a close to the surface roughness of the mirror.
Cubic boron nitride sintered body (PCBN)
PCBN is the CBN particles and the binder sintered together, high temperature resistance, hardness after diamond, with black metal no affinity. From the point of view of development, many new materials need to be processed by PCBN. For example, the use of the car gearbox PCBN gear hob, not only to obtain high productivity, and significantly improve the quality of the processing surface and even become a mirror. According to the data show that the surface of the PCBN rolling gear surface due to the penetration of boron, the hardness is also high. This is confirmed by the experiment of Harbin Institute of technology. Due to the high temperature resistance of PCBN, in the air and water vapor, at 900 DEG C without any changes and stable, even in the 1300 DEG C and Fe, Ni and Co are almost no reaction, do not like the diamond, as rapid wear, then it can still maintain the hardness of hard alloy. Therefore, it can not only cutting hardened steel parts or chilled cast iron and is widely used in high and super high speed cutting work. However, PCBN is not suitable for cutting steel parts, so it is not suitable for. Select tools must pay attention. The size and concentration of the purchase must be taken into account.
The PCBN geometry also have special needs, the general cutting edge chamfering -30 degrees or arc, to prevent the tool tip breakage. Production of PCBN manufacturers a lot of foreign major American GE company, Japan's Sumitomo Electric (strains), DIJET (DIJET), British DeBeers etc., the major domestic Chengdu Tool Research Institute, Guizhou sixth grinding wheel factory, Guilin geological research.
Super hard material coating cutting tool
The emergence of CVD, PVD and other technologies is a major revolution in the field of cutting tools. Its emergence immediately caused a great response in the field of mechanical manufacturing, the ideal cutting tool should be both a hard surface, and a high toughness, coating technology has reached this goal.
The earliest coating material is the material, such as TiN, Al23O, TiC, etc., in recent years, the coating technology has been greatly developed. Super hard material coatings are being used in the market, many products appear in the market, but the domestic is still in the experimental stage, is expected to be very fast