PCD refers to the polycrystalline material formed by sintering diamond micro-powder (with micrometer-level granularity) mixed with a small amount of metal powder (such as Co) under high temperature (1400 ℃) and high pressure.
The PCD composite sheet supplied in the market is a super-hard composite material, where a PDC diamonds layer is firmly bonded to a carbide substrate under high temperature and high pressure. It possesses the high hardness and high wear resistance of PCD, along with the good strength and toughness of carbide.
Therefore, tools made from PCD composite sheets are the most widely used diamond tools, extensively applied in industries such as automotive, aerospace, and construction materials. The reasons why tools made from it have the advantages of high cutting speed, long tool life, and low processing costs in mass workpiece processing are primarily due to the following incomparable performance characteristics of other tool materials.
Extremely high hardness and wear resistance
The hardness of PDC diamonds is 3 to 4 times higher than that of carbide, approaching natural diamond, with wear resistance over 100 times greater. Since diamond grains are freely distributed in all directions without orientation, the hardness and wear resistance are consistent in all directions, making it difficult for cracks to propagate from one grain to another, thereby surpassing single crystal diamond in crack resistance.
Low friction coefficient and high modulus of elasticity
The friction coefficient between PDC diamonds tools and workpiece materials is lower than that of all other tool materials except for single crystal diamond, usually between 0.11 and 0.13. A lower friction coefficient can reduce cutting force and cutting temperature.
The elastic modulus of PCD is significantly higher than that of carbide, so its cutting edge does not easily deform during the cutting process, maintaining the original geometric parameters of the cutting edge to a large extent, and keeping the edge sharp for an extended period.
Good thermal conductivity and low thermal expansion coefficient
The high thermal conductivity and thermal diffusivity of PDC diamonds tools make it easy to dissipate cutting heat during cutting, thus keeping the cutting zone temperature low and extending tool life. The low thermal expansion coefficient prevents significant deformation of the tool during cutting.
Sharp edge and low surface roughness
The cutting edge of PDC diamonds tools is very sharp, usually with a serrated peak value of less than 5μm and a blunt radius of less than 4μm. In most cases, the front surface of PDC diamonds tools is a mirror surface with a surface roughness up to 0.1μm, making it easy for chips to flow out along the front surface, reducing the formation of built-up edges.
To improve engine performance, engine piston materials have transitioned from low-silicon aluminum alloys to medium-silicon aluminum alloys, and even high-silicon aluminum alloys.
The excellent characteristics of PCD lead to wide usage of PDC diamonds tools in processing aluminum alloys, especially high-silicon aluminum alloys. High-silicon aluminum alloys have higher hardness and wear resistance than other aluminum alloys. During cutting, the tool alternately cuts the soft aluminum base and hard silicon particles, leading to quick wear when using ordinary tools. Tools also tend to form built-up edges, worsening processing accuracy and surface roughness.
To avoid built-up edges and work hardening, the cutting edge must be sharp, and the cutting face must be smooth, which perfectly matches the requirements met by PDC diamonds tools.
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