Key words diamond cutter CVD PCD | 2020-03-12 10:21:13
Abstract 【Foreword】 The hardness of a material mainly depends on the strength of the bonding force between atoms in the internal structure of the substance. The stronger the binding force, the greater the resistance to external forces and the higher the hardness of the material. The hardness of a material is closely related to the chemical bond properties of the material.
[Preface] The hardness of a material mainly depends on the strength of the bonding force between atoms in the internal structure of the substance. The stronger the binding force, the greater the resistance to external forces and the higher the hardness of the material. The hardness of a material is closely related to the nature of the chemical bond of the material. The chemical bonds in the material can be divided into three categories according to their characteristics, namely metal parts, covalent bonds and ionic bond materials. Generally speaking, covalently bonded materials have the highest hardness; ionic bonded materials have better chemical stability; metal bonded materials have better comprehensive properties.
The covalent radius of the element is given in the periodic table of the elements. The smaller the radius, the higher the hardness of the material. Through analysis, it can be found that carbon is the most suitable element for generating superhard materials.
From the point of view of valence bond, the semi-full-bonded carbon is tetravalent, and it can either "capture" 4 electrons into a stable state, or "dedicate" 4 electrons to a stable state. Therefore, carbon is usually bonded with covalent bonds and has high hardness.
Considering the coordination structure, the coordination number of diamond has the following characteristics.
The carbon in diamond is free, and it is the most stable tetravalent, so it is impossible to produce polarization.
The carbon atoms in diamond are bonded by covalent bonds, which have typical saturation and directionality.
The coordination number of diamond is 4, which belongs to the accumulation of large balls. Since carbon reaches a stable state, it either "captures" 4 electrons or "dedicates" 4 electrons, that is, its ability to "capture" or "dedicate" electrons is equivalent.
The crystal structure of diamond is shown.
These three figures are the same, but the perspective is different. Each tetrahedron has a carbon atom in the center. It extends four bonds to pull the four carbon atoms at the top corner of the tetrahedron. Top corner. Each unit cell has four tetrahedrons, and the unit cell forms a crystal.
Diamond is the hardest substance in the world, which also proves that it is a special form of compact packing and a favorable form of coordination structure.
At present, there are two types of diamond cutters, namely single crystal diamond cutters and polycrystalline diamond cutters. Natural diamond is used less because of its high price.
Diamond tool features:
Extremely high hardness and abrasion resistance The microhardness of natural diamond reaches 10000HV, which is the hardest substance that has been found in nature. The wear resistance of natural diamond is 80-120 times that of cemented carbide, and the wear resistance of artificial diamond is 60-80 times that of cemented carbide.
The hardness, abrasion resistance, micro strength, easiness of grinding, and the friction coefficient with the workpiece material of anisotropic single crystal diamond crystals are very different. Therefore, the design and manufacture of single crystal When cutting diamond tools, the crystal direction must be selected correctly, and the diamond material must be crystal-oriented. The choice of the rake face and flank face of the diamond tool is an important issue in the design of single crystal diamond tools.
Has a very low coefficient of friction The coefficient of friction between diamond and some non-ferrous metals is lower than other tools, about half of that of carbide tools. Usually between 0.1-0.3.
The cutting edge is very sharp. The blunt circle radius of the cutting edge is generally 0.1-0.5um. Natural single crystal diamond tools can be in the range of 0.002-0.005um. Therefore, natural diamond tools can perform ultra-thin cutting and ultra-precision machining.
Has high thermal conductivity. The thermal conductivity of diamond is 1.5-9 times that of cemented carbide and 2-6 times that of copper.
With a lower coefficient of thermal expansion, the coefficient of thermal expansion of diamond is smaller than that of cemented carbide, which is about 1/10 of that of high-speed steel. Therefore, the diamond tool does not cause great thermal deformation, that is, the change of the tool size caused by the cutting heat is very small, which is particularly important for precision and ultra-precision machining with high requirements for dimensional precision.
Single crystal diamond tool
Single crystal diamond can be divided into natural single crystal diamond and synthetic single crystal diamond. Natural diamond, commonly known as diamond, is one of the hardest natural minerals discovered by mankind. Most high-quality natural diamonds are regular octahedrons or diamond-shaped dodecahedrons, and a few are six-sided cubes or other shapes. They are light-colored and transparent, free of impurities and defects. Has a large refractive index.
Polycrystalline Diamond (PCD) Tool
Artificial single crystal diamond was gradually developed after the 1950s. He used graphite as a raw material, added catalyst, and synthesized by high temperature and high pressure. Artificial polycrystalline diamond (PCD) is a polycrystalline material formed by polymerizing fine diamond powder with a metal binder (such as Co, Ni, etc.). Synthetic polycrystalline diamond is a special powder metallurgy product, and some methods and means of conventional powder metallurgy are borrowed from the manufacturing method.
During the sintering process, due to the addition of additives, bonding bridges with Co, Mo, W, WC, and Ni as the main components are formed between the PCD crystals, and diamond is firmly embedded in a strong framework composed of the bonding bridges. The role of the metal binder is to firmly hold the diamond and give full play to the cutting efficiency of the diamond. In addition, since the grains are freely distributed in all directions, it is difficult for cracks to propagate from one grain to another, which greatly improves the strength and toughness of PCD.
CVD diamond cutter
CVD diamond refers to the synthesis of a diamond film on a heterogeneous substrate (such as cemented carbide, ceramics, etc.) by chemical vapor deposition. CVD diamond has the same structure and characteristics as natural diamond. CVD diamond tool's super hard wear resistance and good toughness make it able to process most non-metallic materials and many non-ferrous metal materials. Such as aluminum, aluminum silicon alloy, copper alloy, graphite, ceramics, and various reinforced glass fiber and carbon fiber structural materials.
-All diamond tools can be ordered and fabricated!
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Henry Wang | Quote Manager
-WhatsApp:+86-13459035657
-Email: ceo@zdiamondtools.com
-Web www.zdiamondtools.com
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