Before selecting and using diamond-coated tools, users must understand the following common knowledge about diamond-coated tools:

The difference between coatings

Amorphous diamond (also known as diamond-like carbon-Annotation) coating is a carbon film deposited by the PVD process. It has both part of the SP3 bond of diamond and part of the SP2 bond of carbon; its film-forming hardness is very high, but it is lower than the hardness of diamond film; its thickness is also thinner than the diamond film we usually deposit. When processing graphite, the life of amorphous diamond-coated tools is 2-3 times longer than that of uncoated carbide tools. In contrast, CVD diamond is a pure diamond coating deposited by the CVD process. 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 accuracy of processing. consistency.

Machining hardened steel

Diamond is made of carbon atoms. When certain materials are heated, carbon atoms are extracted from the diamond and carbides are formed in the workpiece. Iron is one such material. When machining iron group materials with diamond tools, the heat generated by friction will diffuse the carbon atoms in the diamond into the iron, which will cause the diamond coating to fail prematurely due to chemical wear.

Restrictions on tools

It is difficult to guarantee the quality of reground and/or re-coated diamond-coated tools. Because the coating on the surface of the tool is pure diamond, it takes a long time to re-grind the tool with a diamond grinding wheel. In addition, a tool used to grow diamonds. The preparation process will change the chemical characteristics of the surface of the tool. Since the coating requires very precise control of this chemical characteristic, it is difficult to guarantee the effect of the re-coating of the tool.

The life of the tool

Like any other tool, the life of diamond-coated tools varies, depending on the material being cut, the selected feed rate and cutting speed, and the geometry of the workpiece. Generally speaking, the life of diamond-coated tools for processing graphite is 10-20 times longer than that of uncoated carbide tools, and in some cases it may even be longer. In this way, almost any machining task can be completed with one tool, without the need to change the tool due to tool wear, avoiding interruption and recalibration of machining, and thus it is possible to realize unattended machining. In the processing of composite materials, it is entirely possible to obtain a longer tool life.

It is reported that when processing high-density glass fiber, carbon fiber and Gl0-FR4 and other difficult-to-process composite materials, the life of diamond-coated tools can be as high as 70 times that of uncoated carbide tools.

Existing problems

The peeling of the diamond coating can prevent the peeling of the coating. It is a serious problem of diamond-coated tools, and it is also a common problem (especially when processing carbon fiber and other materials), which can cause the tool life to be unpredictable. In the late 1990s, interface chemistry was determined to be an important factor affecting the adhesion performance of diamond coatings. It is possible to reduce or eliminate the spalling of the diamond coating by selecting the chemical characteristics of the cemented carbide with good compatibility, adopting the appropriate pretreatment technology and reasonable deposition reaction conditions, and stably realize the stable wear mode. Observing the normally worn diamond-coated tool under a microscope, it can be found that the diamond is steadily worn to the cemented carbide substrate without chipping or peeling.

This article comes from: Dongguan Guorui Cutting Tools Co., Ltd.www.mjocut.com