Application range and manufacturing method of diamond cutter
With the rapid development of automotive, aerospace and aerospace technologies, the requirements for material properties and processing technology are increasing. New materials such as carbon fiber reinforced plastics, particle reinforced metal matrix composites (PRMMC) and ceramic materials are widely used. These materials have high strength, good wear resistance and low coefficient of thermal expansion, which determines the tool life is very short when machining them. The development of new wear-resistant and stable super-hard cutting tools is a subject of research in many universities, research institutes and enterprises.
Diamond combines many excellent properties such as mechanics, optics, thermals, acoustics and optics. It has extremely high hardness, low friction coefficient, high thermal conductivity, low thermal expansion coefficient and low chemical inertness. It is an ideal material for manufacturing tools. This paper gives an overview of the development of diamond tool manufacturing methods in recent years.
1, the application range of diamond tools
(1) Processing of difficult-to-process non-ferrous materials
When processing non-ferrous metals such as copper, zinc, aluminum and their alloys, the materials are easy to adhere to the tool and the processing is difficult. With the characteristics of low friction coefficient of diamond and low affinity with non-ferrous metals, diamond tools can effectively prevent metal from bonding with tools. In addition, due to the large elastic modulus of the diamond, the deformation of the blade portion during cutting is small, and the deformation of the non-ferrous metal to be cut is small, so that the cutting process can be completed under a small deformation, thereby improving the quality of the machined surface.
(2) Processing of difficult-to-machine non-metallic materials
When processing difficult-to-machine non-metallic materials containing a large number of high-hardness particles, such as glass fiber reinforced plastics, silicon-filled materials, and hard carbon fiber/epoxy composites, the hard spots of the materials cause serious tool wear and are difficult to use with carbide tools. Processing, and the diamond cutter has high hardness and good wear resistance, so the processing efficiency is high.
(3) Ultra-precision machining
With the advent of modern integration technology, machining is moving toward high precision, which puts high demands on tool performance. Due to the small friction coefficient of diamond, low thermal expansion coefficient and high thermal conductivity, it can cut very thin chips, and the chips are easy to flow out. The affinity with other substances is small, the built-up edge is not easy to occur, the heat generation is small, the thermal conductivity is high, and heat can be avoided. The influence of the blade and the workpiece, so the blade is not easy to passivate, the cutting deformation is small, and a higher quality surface can be obtained.
2. Manufacturing method of diamond cutter
At present, there are four main processing methods for diamond: thin film coated tools, thick film diamond welding tools, diamond sintered body tools and single crystal diamond tools.
2.1 film coating tool
A thin film coated tool is a tool made by depositing a diamond film by chemical vapor deposition (CVD) on a collective material of high rigidity and high temperature characteristics.
Since the thermal expansion of the Si3N4 ceramics, the WC-Co cemented carbide, and the metal W is close to that of the diamond, the thermal stress generated during film formation is small, and thus it can be used as a base material of the blade body. In the WC-Co cemented carbide, the presence of the binder phase Co tends to form graphite between the diamond film and the matrix to reduce the adhesion strength, and pretreatment is required before the deposition to eliminate the influence of Co (generally by acid etching to Co). .
The chemical vapor deposition method uses a certain method to activate a gas containing a C source, and at a very low gas pressure, carbon atoms are deposited in a certain region, and the carbon atoms form a diamond phase during aggregation and deposition. At present, the CVD method for depositing diamond mainly includes: microwave, hot filament, DC arc spray method and the like.
The advantages of diamond film are that it can be applied to a variety of geometrically complex tools, such as blades with chips, end mills, reamers and drill bits; it can be used to cut many non-metallic materials, with small cutting force and small deformation during cutting. The work is stable, the wear is slow, and the workpiece is not easily deformed. It is suitable for finishing with good workpiece material and small tolerance. The main disadvantage is that the adhesion of the diamond film to the substrate is poor, and the diamond film tool does not have regrind.
2.2 diamond thick film welding tool
The manufacturing process of diamond thick film welding tools generally includes: preparation of large-area diamond film; shape and size required for cutting diamond film into tool; welding of diamond thick film and tool base material; grinding and polishing of diamond thick film cutting edge . (1) Preparation and cutting of diamond thick film
A commonly used method for preparing a diamond thick film is a DC plasma jet CVD method. The diamond is deposited on the WC-Co alloy (the surface is mirror-finished), and the diamond film automatically falls off during the cooling of the substrate. This method has a fast deposition rate (up to 930 μm/h), and the lattice is relatively tightly bonded, but the growth surface is rough. The high hardness, wear resistance and non-conductivity of the diamond film determine that its cutting method is laser cutting (cutting can be carried out in air, oxygen and argon). Laser cutting not only cuts the diamond thick film into the required shape and size, but also cuts the back angle of the tool, with narrow slits and high efficiency.