PCD refers to a polycrystal formed by mixing diamond micro-powder (with a particle size of micrometers) and a small amount of metal powder (such as Co) and then sintering at high temperature (1400 ℃) and high pressure.
The PCD composite sheet supplied as a commodity on the market is a super-hard composite material that is firmly combined with a cemented carbide substrate by a polycrystalline diamond layer under high temperature and pressure. It has the high hardness and high wear resistance of PCD. And both the good strength and toughness of cemented carbide.
Therefore, the tool made of PCD composite sheet is the most widely used diamond tool, which is widely used in the automotive, aerospace, building materials and other industrial fields. The tool made with it has the advantages of high cutting speed, long tool life and low cost of mass machining workpieces, mainly because it has the following performance characteristics that other tool materials cannot match.
PCD tool performance characteristics
1. Very high hardness and wear resistance
The hardness of polycrystalline diamond is 3 to 4 times higher than that of cemented carbide, close to natural diamond, and its wear resistance is more than 100 times higher. Because the diamond grains are freely distributed in all directions and have no directionality, the hardness and resistance in all directions are The abrasiveness is consistent, it is difficult for cracks to propagate from one grain to another, and its crack resistance is better than that of single crystal diamond.
2. Low coefficient of friction and high modulus of elasticity
The coefficient of friction between the PCD tool and the workpiece material is lower than that of other tool materials except for single crystal diamond, usually between 011 and 013. The small friction coefficient can reduce the cutting force and reduce the cutting temperature.
The modulus of elasticity of PCD is much larger than that of cemented carbide, so its cutting edge is not easily deformed during the cutting process, and can maintain the original geometric parameters of the cutting edge to a large extent, and keep the cutting edge sharp for a long time.
3. Good thermal conductivity and low thermal expansion coefficient
High thermal conductivity and thermal diffusivity make PCD tools easy to lose cutting heat during cutting, so that the temperature in the cutting zone will be lower and the tool life will be long. The low coefficient of thermal expansion makes the tool less prone to major deformation during the cutting process.
4. Sharp edge and low surface roughness
The edge of PCD tool is very sharp. Generally, the peak value of the edge is less than 5μm, and the radius of the blunt edge of the edge is less than 4μm. In most occasions, the rake face of PCD tools is mirrored, and the surface roughness can reach 0101μm, which can make chips flow out easily along the rake face and reduce the generation of built-up edge.
Application of PCD Tool in Piston Machining
In order to improve engine performance, the engine piston material is changed from low-silicon aluminum alloy to medium-silicon aluminum alloy, and even high-silicon aluminum alloy is used.
The excellent characteristics of PCD make PCD tools widely used in processing aluminum alloys, especially high-silicon aluminum alloys. The hardness and wear resistance of high-silicon aluminum alloy are higher than other aluminum alloys. When cutting, the tool alternately cuts soft aluminum base and hard silicon particles, and ordinary tools are easy to wear. At the same time, the tool is also prone to build-up edge, which will deteriorate the machining accuracy and surface roughness.
In order to avoid built-up edge and work hardening, the cutting edge must be sharp and the cutting face must be smooth. PCD tools meet these requirements.
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