The machining methods of diamond tools are as follows: thin-film coated tools, thick-film diamond welding tools, diamond sintered body tools, and single-crystal diamond tools.
Thin-film coated diamond cutters thin-film coated diamond cutters are made by deposition of diamond films by chemical vapor deposition (CVD) on collective materials with good rigidity and high-temperature properties. As the thermal expansion system of SiN4 series ceramics, WC+Co series cemented carbide and metal W is close to that of the diamond, the thermal stress generated during film preparation is small, so it can be used as the matrix material of the cutter body.WC+Co is a kind of cemented carbide. The presence of Co in the bond phase makes it easy to form graphite between the diamond film and the matrix and reduce the adhesion strength.
Therefore, pretreatment is needed before the deposition to eliminate the influence of Co (generally, the Co is removed by acid corrosion). The chemical vapor deposition method is to activate the gas containing C source in a certain way and deposit carbon atoms in a certain area at a very low gas pressure. The carbon atoms form a diamond phase in the process of condensation and deposition. At present, the CVD methods for diamond deposition mainly include microwave, hot filament, and dc arc injection. The advantage of diamond film is that it can be used in a variety of tools with complex geometry, such as blades with chips, end milling cutters, reamers, and drill bits. Can be used to cut many non-metal materials, when cutting, cutting force is small, deformation is small, smooth work, wear slowly, the workpiece is not easy to deformation, suitable for the workpiece material is good, small tolerance finishing.
The fabrication process of diamond thick film welding tool generally includes the preparation of large-area diamond film; Cut the diamond film into the shape and size required by the cutting tool; Welding of diamond thick film and tool base material; The grinding and polishing of the cutting edge of diamond thick film tool. The diamond is deposited on WC+Co alloy (the surface is processed in the mirror), and the diamond film falls off automatically during the cooling process of the matrix. The deposition rate of this method is fast (up to 930 m/h), the bonding between lattices is close, but the growth surface is rough. The diamond film has high hardness, abrasion resistance, and non-conductivity, which determines its cutting method is laser cutting (cutting can be done in the environment of air, oxygen, and argon). The use of laser cutting can not only cut the diamond thick film into the required shape and size but also can cut the tool Angle, which has the advantages of the narrow slit, high efficiency. There is a high interface between diamond and common metal and its alloy, so that diamond cannot be infiltrated by a common low melting point alloy, and the weldability is very poor.
At present, the weldability between diamond and metal is improved mainly by adding carbide forming elements in copper-silver alloy solder or by metalizing diamond surface. Solder generally USES Ti – containing copper-silver alloy, without flux in inert gas or vacuum welding.The commonly used filler metal composition Ag=68.8wt%, Cu=26.7wt%, Ti=4.5wt%. The commonly used preparation methods are arc smelting and powder metallurgy. The heating temperature is generally 850℃, holding for 10 minutes, slow cooling to reduce internal stress. Metallization of a diamond surface is to coat the diamond surface with metal by surface treatment technology so that its surface has the performance of metal or metal-like. Generally, Ti is plated on the surface of the diamond, and Ti reacts with C to form TiC. TiC ag-cu alloy solder has better wettability and bonding strength. At present, the commonly used methods of titanium plating are vacuum physical vapor deposition (PVD mainly includes vacuum evaporation, vacuum sputtering, vacuum ion plating, etc.), chemical vapor deposition and powder covering sintering. The temperature of the diamond during the process of plating is lower than 500℃. There is no chemical metallurgy between the coating and diamond.CVD method Ti and diamond chemical reaction to form a strong metallurgical bond, the reaction temperature is high, damage diamond.
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