Application and Prospect of diamond and ultra hard materials (3)
2015/9/3 13:44:51
Problem and Prospect
Each cutting tool material in the development of some abnormal, it must continue to explore and research. Each material has different characteristics, in use should be based on the characteristics of tools and materials, and even processing conditions to choose a reasonable processing method.
As is well known, diamond is the hardest material in the world. As a cutting tool, it is an ideal material, so it is widely used. But it has an affinity with the black metal, and at about 700 degrees, the phenomenon of graphite, the wear of the diamond will accelerate, so only suitable for cutting non-ferrous metals and non-metallic materials. But people have been trying to break the forbidden area, such as LLNL National Laboratory Cassteven professor once adopted carbon rich environment, direct cutting of ferrous metals, certain effect; Harbin Engineering University in China using liquid nitrogen spray; cryogenic cutting of ferrous metals. It has also achieved some results, some people think that the diamond with a certain amount of boron can be cut black metal, in short, in the near future, there may be a breakthrough.
The cutting tool of the super hard material coating is earlier than the ceramic coating, but there are still many problems to be solved, especially the strength of the adhesive force, which directly affects the life of cutting tools. In the ceramic coating has also the occurrence of this kind of problem, such as cutting tools in the coating before the clean processing; and as the cutting tool of the edge grinding, not allow edge annealing, not allowed to leave a burr, also has the use of multi coating method to solve, but in the super hard coating also need to be new development.
The birth of ceramic coating technology is a major development of cutting tool material, and the super hard material coating again broke through, so that almost all of the cutting tools to the more ideal field.
PCD and PCBN is the current application of cutting tools, the development of its technology is still subject to attention, such as foreign products, in the manufacture of electric spark line cutting will be directly cut into the shape of the blank, but the domestic billet can only be part of the hard alloy part cut, and then cut the rest. Generally this kind of cutting tools can achieve the surface roughness is lower, while the application of the GE company's fine blade, then can be close to the mirror, the main reason is that the grain size of the super fine. The interface is increased, and the cutting edge can be obtained.
The synthesis of thick film diamond is a breakthrough in cutting tool material. It will provide more chances for the application of natural diamond in the field of ultra precision machining. This is not only because its performance is close to that of natural diamond, but it also has a low cost. A very good prospect for a country with scarce diamond deposits. The matrix of diamond deposition must be carefully cleaned before deposition. If it is hard alloy, cobalt based hard alloy is generally used, it has the effect on the density of the diamond synthesis, the density is low, the deposition quality is poor, and the adhesion of the coating is low. So must take the method of corrosion to remove the surface of cobalt.
Because cobalt is deposited on the interface between the substrate and the substrate, the non diamond material, such as graphite, etc., will be generated. A lot of carbon diffusion in cobalt, and will become the interface crack formation reasons. The thermal expansion coefficient of WC sintered with cobalt is 5 * 10-6/ ~ 6 * 10-6/, and the ratio of 3.1 * 10-6/ is larger than that of diamond. From these conditions, it is still worth exploring to improve the bond strength of the hard alloy containing cobalt. Recently, Professor Yoshikawa Masanori of Tokyo Institutet of Technology proposed that the sintering process of WC powder can be produced without cobalt, so that the bonding force of the powder can be improved significantly, and the deposition of diamond particles is small.
Artificial synthesis of large single crystal diamond industry has been a breakthrough, but the cost is still very high, there is still to be developed. In short, the development of super hard materials will cause tremendous changes in mechanical manufacturing, will undoubtedly make a greater contribution to twenty-first Century.