Tool coating technology new bright spot

Diamond coating is a new tool coating material which has been studied successfully in recent years. Diamond coated carbide blade and solid carbide multitool in printed circuit board processing and silicon material such as aluminum alloy have achieved great success, the knives' service life several times higher than that of uncoated cemented carbide cutting tools.

Us scientists have developed a new way to produce synthetic diamond (PCD) cheaply and quickly, which is expected to make diamond coating more widely used in industry. Although the application of the new technology to produce the largest diamond particle size is less than 10 nm, it is impossible to create a gem grade diamond with it, but it can reduce the production cost of diamond coating, easy to manufacture the material hardness performance with special needs, such as artifacts, such as diamond coated tools, brake pad, etc.

The component of diamond is pure carbon. So far, silicon has been removed from silicon carbide to make nano-sized gold snags. However, the existing technology needs to be carried out under high pressure or through high-energy plasma injection method, which has high production cost and low output. Scientists at drexel university in Texas have successfully produced nanoscale diamonds at one atmosphere of pressure. The researchers put silicon carbide in the mixture of hydrogen and chlorine, and then to be heated to 1000 ℃. When chlorine reacts with silicon, the remaining carbon atoms reassemble to form nanoscale films of carbon materials. Among them are diamond crystals, graphite, carbon nanotubes and hexagon diamond, etc. Hydrogen makes the conversion stable.

The hardness of the carbon film produced is basically the same as that of diamond. Moreover, its special structure can make it have the performance of various USES, such as permeable, conductive and so on. This can not only reduce the manufacturing cost of traditional diamond coating products, but also expand the application scope of diamond coating, such as flat panel display, molecular filter, etc.

CVD diamond coating USES many diamond synthesis techniques. The most common methods are hot wire method, microwave plasma method and d and c plasma injection method. Diamond coated carbide cutting tools have been produced by improving the coating method and bonding of coatings, and play an important role in the processing of non-ferrous and non-metallic materials.

2. Cubic boron nitride (CBN) coating

Cubic boron nitride (CBN) is the high temperature and high pressure of boron nitride phase, it is the second most hard materials (second only to diamond up to 60 gpa), its structure is similar to the diamond, but CBN for steel and iron, hot oxidation environment with chemical inertness, when the oxidation, forming a thin layer of boron oxide. This oxide layer provides chemical stability to the coating. Therefore, it has obvious advantages in processing hard iron (50 ~ 65HRC), gray iron, high temperature alloy and sintered powder metal.

Many researchers have tried to deposit cubic boron nitride films using CVD and PVD technology. Test results show that. Some progress has been made in synthesizing CBN phase, good adhesion to hard alloy matrix and appropriate microhardness. At present, the maximum thickness of cubic boron nitride film deposited on hard alloy matrix is only 0.2-0.5m. In order to achieve commercialization, reliable technology must be adopted to deposit high purity and economic CBN films. Its film thickness should be 3 ~ 5 m, and its effect should be confirmed in actual metal cutting process.

The use of CVD coated carbide tool has developed rapidly. The toughness of mt-cvd coating exceeds that of ht-cvd coating. However, in addition to depositing the TiCN coating, it is not possible to extend the coating technology. Plasma - assisted CVD coatings have similar advantages, but their composition is limited. New coating components are expected to be produced by cryogenic deposition.

The development of new PVD coating materials, including PVD coating Al2O3 and PVD multi-coating, will expand the application of PVD coating tools. This will be a challenge for CVD coatings.

The CVD and PVD composite coating is fully realized. TiN/NbN. The superlattice coatings of TiN/Ni and TiN/NiCr have higher hardness than those of single-phase nitrides and are expected to be used in metal cutting. The improvement of process economy will increase the possibility of using diamond coated tool. Their applications, however, are limited to non-ferrous metals. The breakthrough potential lies in cubic boron nitride (CBN) coated carbide cutting tools. This material can be used to process more than 75 percent of the iron material that is processed today.

3. HPPC coating

In 1986, the university of Wisconsin developed a new technology. The object to be processed is placed in a plasma environment with high voltage pulses to inject ions into the surface of a three-dimensional object. The full name of this technology is Plasma Source Ion Implantation, or PSII technology. September 1993. At the SMMID93 international conference in kanazawa, Japan. A special speech by Dr. J R Conrad. The technology was introduced to Japan for the first time. From 1998 to 2000, Japan organized industry, universities and research institutions to cooperate with each other, and after three years of trial and error. Finally, a new coating technology was developed based on PSII. Hybrid Pulse Plasma Coating system. HPPC technology for short.

PSII technology is used to inject ions into the surface of a processed object in a static state (no rotation or revolution) in a three-dimensional complex shape to improve the surface material performance. PSII technology works by applying a negative high voltage to an object in a plasma environment to form a non-electronic envelope around the object, with a high voltage applied through the envelope. The ions at the plasma end are injected vertically into the surface of the object. In the newly developed HPPC system, the internal volume of the vacuum container is 1m3, and the applied voltage of the negative high-voltage pulse is 20kV. The pulse width is 5 ~ 20 s. In HPPC system, the pulse of raw gas, the formation of high density pulse plasma, the application of high voltage pulse and the vacuum exhaust are all controlled by pulse.

When toluene gas is used as raw material gas in HPPC system, the DLC film can be plated on the hard alloy matrix by applying pulse voltage when PSII is mixed. The test shows that the voltage of mixing is increased. DLC coating with good binding strength can be obtained. In the process of film formation. DLC coatings with high binding strength over 100N can be obtained with proper conditions. D is the depth of groove, D is the width of opening part, and D/ D is the aspect ratio. D/ D =4 for uniform coating test. The sample size is 10mm * 10mm * 5mm, and the traditional ion plating method is adopted. Effective coatings can be formed only when D/ D =1. HPPC system is adopted. Effective plating film can be formed at the bottom and side wall of deep groove. In addition, ceramic coating tests were carried out on organic metal (Si(OC2H6)4 after gasification. The results show that. The approach is different. The film thickness ratio is also very different. For example, the maximum thickness ratio of coating obtained by plasma CVD process is 2.0. The thickness ratio of the coating obtained by using HPPC system was 1.3 at the maximum, and the uniformity of the coating was significantly better than that of the former.