Artificial single crystal diamond was gradually developed after the 1950s. It is synthesized from graphite as raw material, added with a catalyst, and subjected to high temperature and ultra-high pressure. Artificial polycrystalline diamond (PCD) is a polycrystalline material formed by the polymerization of diamond powder using metal binders such as Co, Ni, etc. Artificial polycrystalline diamond is a special type of powder metallurgy product, which draws on some methods and means of conventional powder metallurgy in its manufacturing method.
During the sintering process, due to the addition of additives, a bonding bridge composed mainly of Co, Mo, W, WC, and Ni is formed between PCD crystals, and diamonds are firmly embedded in the sturdy framework formed by the bonding bridge. The function of metal binder is to firmly hold the diamond and fully utilize its cutting efficiency. In addition, due to the free distribution of grains in various directions, it is difficult for cracks to propagate from one grain to another, which greatly improves the strength and toughness of PCD。
In this issue, we will briefly summarize some of the characteristics of PCD insert.
1. Ultra high hardness and wear resistance: unparalleled in nature, materials have a hardness of up to 10000HV, and their wear resistance is nearly a hundred times that of Carbide insert;
2. The hardness, wear resistance, microstrength, difficulty in grinding, and friction coefficient between anisotropic single crystal diamond crystals and workpiece materials vary greatly in different crystal planes and orientations. Therefore, when designing and manufacturing single crystal diamond tools, it is necessary to correctly select the crystal direction, and crystal orientation must be carried out for diamond raw materials. The selection of the front and back cutting surfaces of PCD cutting tools is an important issue in designing single crystal PCD lathe tools;
3. Low friction coefficient: Diamond inserts have a lower friction coefficient when processing some non-ferrous metal materials compared to other inserts, which is about half of that of carbides, usually around 0.2.
4. The PCD cutting edge is very sharp, and the blunt radius of the cutting edge can generally reach 0.1-0.5um. And natural single crystal diamond tools can be used in the range of 0.002-0.005um. Therefore, natural diamond tools can perform ultra-thin cutting and ultra-precision machining.
5. The coefficient of thermal expansion of diamond with lower coefficient of thermal expansion is smaller than that of cemented carbide, about 1/10 of that of high-speed steel. Therefore, diamond cutting tools do not produce significant thermal deformation, meaning that the change in tool size caused by cutting heat is minimal, which is particularly important for precision and ultra precision machining with high dimensional precision requirements.
Application of diamond cutting tools
PCD insert is mostly used for high-speed cutting/boring/milling of non-ferrous metals and non-ferrous metal materials, suitable for processing various wear-resistant non-metallic materials such as glass fiber and ceramic materials; Various non-ferrous metals: aluminum, titanium, silicon, magnesium, etc., as well as various non-ferrous metal finishing processes;
Disadvantages: poor thermal stability. Although it is the cutting tool with the highest hardness, its limited condition is below 700 ℃. When the cutting temperature exceeds 700 ℃, it will lose its original ultra-high hardness. This is why diamond tools are not suitable for machining ferrous metals. Because of the poor chemical stability of diamonds, the carbon element in diamonds will interact with iron atoms at high temperatures, and will be converted into graphite structure, greatly increasing the damage of tools.
Post time: May-17-2023