Engineering application of CVD diamond film

27 September 2020

Engineering application of CVD diamond film

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1. Milling CFRP


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Carbon fiber reinforced resin matrix composite (CFRP) is widely used in aerospace, aviation, automotive and energy fields with excellent properties such as light weight, high strength, fatigue resistance, corrosion resistance and strong designability.Generally, the formability of CFRP parts mainly adopts near net forming technology. However, milling is often needed after forming because the precision or assembly requirements cannot be met.CFRP is a typical difficult material to be machined. In the process of machining, the carbon fiber reinforced with high hardness and low thermal conductivity will wear the tool severely. Meanwhile, the local high temperature in the cutting area will accelerate the tool edge wear.After milling, the material is easy to produce burr, tear, stratification and other machining defects.The traditional carbide milling cutter can not meet the processing requirements, so it is necessary to increase the wear-resisting coating.Due to its advantages of high hardness, high thermal conductivity and low friction coefficient, diamond film has become an ideal material for the manufacture of wear-resistant coatings for CFRP tools


The preparation process of CVD diamond coated cutter is not limited by the shape of the cutter. After coating, the cutter can be used directly. It is suitable for preparing the cutter with complex shape, such as milling cutter, drill bit, etc.


Yang Xiaofan on the basis of the study of the machining characteristics of CFRP, carbide end mill, but at the same substrate, respectively, the preparation of the coarse grain, fine crystal, crystal three different composite coating process of CVD diamond film.Under the same cutting conditions, the milling test of carbon fiber composite material shows that the diamond coated milling cutter with composite crystal technology has the longest service life, which is about 1.35 times of coarse crystal diamond coated milling cutter and 1.59 times of fine crystal diamond coated milling cutter, which is more suitable for the milling of carbon fiber composite material.


2. Processing Zirconia Ceramics


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Zirconia ceramics have excellent physical and chemical properties and are widely used in aerospace, aviation, national defense, energy and other fields. For example, in the field of oral restoration, all-ceramic teeth made from it have become a popular product in the market. It can be well adapted to the tooth work and environment, and its appearance also meets the needs of consumers. However, due to its high hardness, it is difficult to mill and process, and the complexity and precision required for production are also high. Therefore, the development of a tool can complete the processing of zirconia ceramics under the requirements of high efficiency, high quality and economy. Very meaningful research topic.


Wang Haiwang and others used the bias-enhanced hot-wire chemical vapor deposition method to deposit three different diamond film coatings on the cemented carbide sheet and the cemented carbide ball end milling cutter, which are micro-diamond film (MCD) and nano-diamond film (NCD). ) And micron nano composite diamond film (MNCD).

Through the friction experiment, it is found that the friction coefficient curves of the three kinds of CVD diamond film coatings and the zirconia ceramic ball are relatively similar. At the beginning of the friction process, the friction coefficient is relatively large, and then in the process of friction, the friction coefficient gradually decreases, until the friction coefficient becomes relatively stable.


The cemented carbide is different from the first three in that the friction coefficient is relatively small at the beginning of the friction process, and then as the friction process progresses, the friction coefficient gradually increases, but the friction coefficient will become relatively stable in the end.

Through cutting experiments, it is found that the wear of diamond-coated tools is much smaller than that of uncoated tools. Comparing three different diamond film coatings, diamond particles that have not been polished can still be observed on the surface of the MCD film. The wear morphology of the NCD and MNCD films are very similar, and the wear amount is not much different, which is smaller than the MCD film. .


3. Drawing die


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The metal wire industry is my country's main traditional industry, and drawing dies are important consumables for metal wire manufacturers. The performance of the drawing die determines the quality, production efficiency and production cost of the metal wire. At present, the molds used in the wire industry are mainly two categories: cemented carbide molds and polycrystalline diamond molds. Cemented carbide molds have a short life, easy to stick materials, and low production efficiency; polycrystalline diamond molds are expensive, making it very difficult to make larger-sized molds and special-shaped molds, and has poor toughness. The use of CVD diamond coating technology to make diamond-coated drawing dies overcomes the shortcomings of hard alloy drawing dies that are not wear-resistant and polycrystalline diamond drawing dies have poor toughness and become a new generation of drawing dies. According to observations, in actual use of the diamond-coated drawing die, the failure of the diamond-coated drawing die is not due to excessive dimensional changes caused by wear, but the rough surface exposed after the diamond coating is partially peeled off, causing the wire surface to scratch and cause failure , It is essentially different from the failure of ordinary cemented carbide molds and polycrystalline diamond molds.








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