(1) The difference between CVD diamond coating and amorphous diamond coating
Amorphous diamond (also known as diamond-like carbon) coatings are carbon films deposited using the PVD process. It not only has a part of diamond SP3 bond, but also has a part of carbon SP2 bond; its film hardness is very high, but it is lower than that of diamond film; its thickness is also thinner than the diamond film that we usually deposit. When machining graphite, the lifetime of amorphous diamond-coated tools is 2-3 times that of uncoated carbide tools. In contrast, CVD diamond is a pure diamond coating deposited by CVD. The tool life when machining graphite is 12-20 times that of cemented carbide tools, which can reduce the number of tool changes and improve the reliability and accuracy of machining. consistency.
(2) Hardened steel cannot be machined with diamond tools
Diamond consists of carbon atoms. When certain materials are heated, carbon atoms are drawn from the diamond and form carbides in the workpiece. Iron is one of such materials. When diamond tools are used to process iron-based materials, the heat generated by the friction causes carbon atoms in the diamond to diffuse into the iron, causing the diamond coating to prematurely fail due to chemical wear.
(3) The quality of diamond-coated tools that are reground and/or recoated is difficult to guarantee
Since the coating produced on the tool surface is pure diamond, it takes a long time to re-grind the tool with a diamond grinding wheel. In addition, the tool used to grow the diamond. The preparation process will change the chemical properties of the tool surface. Because the coating requires very precise control of this chemical property, the re-coating effect of the tool is difficult to guarantee.
(4) The life of diamond-coated tools varies
As with any other tool, the life of diamond-coated tools varies, depending on the material being cut, the feed rate and cutting speed selected, and the geometry of the workpiece. In general, diamond-coated cutters for processing graphite are 10-20 times longer than uncoated carbide cutters and may even be longer in some cases. In this way, you can use a single tool to perform almost any machining task, without the need for tool change due to tool wear, to avoid machining interruptions and recalibration, which makes it possible to achieve unattended processing. It is also entirely possible to obtain long tool life in the processing of composite materials.
According to reports, during the processing of high-density glass fiber, carbon fiber, and G10-FR4 difficult-to-machine composites, the lifetime of diamond-coated tools can be as much as 70 times that of uncoated carbide tools.
(5) The peeling of the diamond coating can be prevented
Coating flaking is a serious problem for diamond coated tools and is a common problem (especially when processing carbon fiber and other materials), which can lead to unpredictable tool life. In the late 1990s, the interface chemistry was determined to be an important factor affecting the adhesion properties of diamond coatings. By selecting good compatibility of the cemented carbide chemical properties, proper pretreatment technology and reasonable deposition reaction conditions, it is possible to reduce or eliminate the spalling of the diamond coating and stably achieve a stable wear pattern. Looking at the normal wear of the diamond-coated tool under a microscope, it was found that the diamond was stably worn down to the cemented carbide substrate without chipping or peeling.