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Common knowledge of diamond coated tools

2019-05-10

  Before choosing and using diamond tools, users must understand the following common sense about diamond tools:

  (1)The difference between CVD diamond coating and amorphous diamond coating

  Amorphous diamond (also known as diamond-like carbon) coating is a carbon film deposited by PVD process. It has a part of diamond SP3 bond and a part of carbon SP2 bond; its film hardness is very high, but lower than the hardness of diamond film; its thickness is also thinner than the diamond film we usually deposit. When processing graphite, the lifetime of amorphous diamond coated tools is 2-3 times that of uncoated cemented carbide tools. In contrast, CVD diamond is a pure diamond coating deposited by CVD. The tool life when processing graphite is 12-20 times that of cemented carbide tools, which can reduce the number of tool changes and improve the reliability and precision of machining. consistency.

  (2)Cannot process hardened steel with diamond tools

  Diamond is composed of carbon atoms. When some materials are heated, they absorb carbon atoms from the diamond and form carbides in the workpiece. Iron is one of these materials. When machining iron-based materials with diamond tools, the heat generated by the friction causes the carbon atoms in the diamond to diffuse into the iron, causing the diamond coating to fail prematurely due to chemical wear.

  (3)The quality of diamond-coated tools that are reground and/or heavily coated is difficult to guarantee. Because the coating produced on the tool surface is pure diamond, it takes a long time to regrind the tool with a diamond grinding wheel. In addition, the tool used to grow the diamond. The preparation process changes the chemical properties of the tool surface. Since the coating requires very precise control of this chemical property, the effect of tool recoating is difficult to guarantee.

  (4)Diamond coated tools have different life spans

  As with any other tool, the life of a diamond-coated tool varies, depending on the material being machined, the feed rate and cutting speed selected, and the geometry of the workpiece. In general, the life of a diamond-coated tool that processes graphite is 10-20 times longer than that of an uncoated cemented carbide tool, and in some cases may even be longer. In this way, almost any machining task can be performed with a single tool without the need to change the tool due to tool wear, avoiding machining interruptions and recalibration, making it possible to achieve unattended machining. It is also possible to achieve longer tool life in the processing of composite materials.

  It has been reported that diamond coated tools can last up to 70 times longer than uncoated cemented carbide tools when processing difficult-to-machine composites such as high-density glass fibers, carbon fibers, and G10-FR4.

  (5)Peeling of diamond coatings can prevent coating flaking from being a serious problem for diamond coated tools and a common problem (especially when machining materials such as carbon fiber), which can lead to unpredictable tool life. In the late 1990s, interfacial chemistry was identified as an important factor affecting the adhesion properties of diamond coatings. By selecting compatible carbide chemistry, proper pretreatment techniques, and reasonable deposition conditions, it is possible to reduce or eliminate spalling of the diamond coating and achieve a stable wear pattern. Observing a normally worn diamond coated tool under a microscope, it was found that the diamond was stably worn up to the cemented carbide substrate without chipping or peeling.


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