As long as the industrial and precision machinery industries, precision machining, ultra precision cutting and increased use of hard cutting materials, superhard cutting tool materials has been used widely. Hard material tool with high efficiency, long life and processing quality and good features, mainly used for finishing the past, in recent years as improved artificial superhard cutting tool materials, production processes, control of the purity and grain size of raw materials used composite materials and technology so hot, expanding range of applications, in addition to finish suitable for general and semi-finished, it can also used for roughing, is internationally recognized as the most promising contemporary improve the productivity of the tool material . Use of superhard materials of steel, cast iron, nonferrous metals and alloys such as parts, the cutting speed an order of magnitude higher than carbide, carbide tool life than high scores and even hundreds of times. At the same time its appearance, but also the concept of the traditional process changes, use of super-hard cutting tool can often directly, milling instead of grinding (or polishing), the hardened parts processing, can be used instead of a single process multi-channel processes, shorten process .

Overview of superhard cutting tool materials

Super-hard cutting tool material is the natural diamond and hardness, with similar properties of synthetic diamond and CBN (cubic boron nitride). As the price of natural diamond is more expensive, so most of the production of synthetic polycrystalline diamond with (PCD), polycrystalline cubic boron nitride (PCBN), and their composites.

Back in the '50s, the United States on the use of synthetic diamond powder and CBN powders at high temperature, high pressure, the role of catalyst and binder and sintered into polycrystalline blocks of larger size as the tool material. After South Africa Day Bill (DeBeers) company, the former Soviet Union and Japan have developed. The early 70s introduced the diamond or CBN and carbide composite film, which is sintered cemented carbide substrate or a layer of 0.5mm ~ 1mm suppress the PCD or PCBN made to solve the bending of super-hard tool materials low intensity, set the difficulty of welding problems, so that the application of super-hard tool into the practical stage. At present, there was the synthetic single crystal diamond, and with CVD (chemical vapor deposition) method of diamond film coating and diamond films and other functional materials, greatly broadened the applications of superhard tool materials.

China's super-hard tool materials research and application began in the 70s, and was built in 1970 in Guiyang, China's first super-hard materials and products, specializing in the production plant - the sixth Grinding Wheel Factory, from 1970 to 1990 for the past 20 years , super-hard materials only from 460,000 kt output to 35 million karats. 90's super-hard materials before and after the production of many specialized plants introduced from abroad a set of super-hard material synthesis equipment and technology, rapid production development, to 1997, annual production of synthetic diamond in China had reached 500 million karats around, CBN annual production of 8000000 kt, jumping to the world's largest producer of super-hard materials first.

Super-hard cutting tool material properties

Diamond has a very high hardness and wear resistance, their hardness up to 10000HV, is the hardest tool materials materials. Same time, it's friction coefficient is small, with no affinity for non-ferrous metals, chip out easily, high thermal conductivity, not easy to produce cutting BUE, good surface quality. Effective processing of non-ferrous metal materials and nonmetal materials, such as copper, aluminum and other nonferrous metals and alloys, ceramics, sintered carbide end, a variety of fiber and particle reinforced composites, plastics, rubber, graphite, glass and a variety of wear-resistant wood (especially solid wood and plywood and other composite materials).

Diamond drawback is poor toughness, low thermal stability. 700 ~ 800 when the carbonation is easy, so not suitable for machining ferrous materials. Because the iron atoms at high temperature is easy and the role of the carbon atoms were converted to the graphite structure. In addition, use it when cutting nickel-based alloys, the same will quickly wear.

CBN is second only to diamond hardness (up to 8000HV ~ 9000HV), and high thermal stability (up to 1250 ~ 1350 ), the chemical inertia of the big iron group elements, anti-bonding ability, and can use the diamond grinding wheel cutting blade, it is suitable for processing a variety of hardened steel, thermal spraying materials, chilled cast iron and more than 35HRC cobalt and nickel-based and other difficult to cut materials.

Superhard tool materials application prospect

Superhard cutting tool materials is an advanced tool materials, the production has broad application prospects. Artificial superhard cutting tool materials, the present single crystal of the coarse particles, high-strength, multi-direction. U.S. industrial production are now available for GE, a 6 carat diamond (about 10mm), the largest heavy particles up to 11.14 kt. PCD is the large diameter, fine-grained, high impact resistance, high thermal stability of the direction.

PCD has the largest diameter up to 74mm, and then laser cut into any shape needed. PCD particle size goods 2 ~ 25 m; finer particles, the better the quality of the cutting edge; particles larger, longer tool life. PCBN products produced by DeBeers, the largest diameter of 101.6mm, can process high-hardness materials 70HRC. In addition, the patent describes the United Kingdom, the United Kingdom has developed a PCD and PCBN inserts in the outer surface layer with a CVD deposition of nickel, copper, titanium, cobalt, chromium, tantalum mixtures, as well as titanium nitride or titanium carbide protection coating, the wear resistance of PCD and PCBN inserts than ordinary 4 times higher.

Thick film CVD diamond film and developed in recent years of new functional materials, even though production has yet to mature, but because of its excellent performance, with a wide range of uses.

Natural and synthetic single crystal diamond and PCD and TFD exists between the cross-cutting applications, they can complement each other to some extent, be based on different circumstances, in particular, cost performance to be used. Expected in the new century, super-hard tool material CBN and diamond will be more applications may be found to create new varieties of tool material with superior performance. According to Lellond company, they developed a ceramic + CBN's super-hard by the composite, ceramic and CBN which both the advantages of two materials, high-speed processing of high ideal material for hard wear resistant cast iron. Another example is the use of polycrystalline diamond synthesized from graphite body, and today's diamond for the C12, existing research, isotopes C13 and C60 are more rigid. A few years ago, Wuhan University, developed a C3N4/TiN film also has a hard material nature, with its coated in high-speed steel drill, the drill life can be greatly increased. It can be expected in the future as new types of more difficult to cut materials applications, will promote the further development of superhard cutting tool materials and application.