Before selecting and using diamond tools, users must understand the following common knowledge about diamond tools:
Difference of coating
Amorphous diamond coating is a kind of carbon film deposited by PVD process. It has a part of SP3 bond of diamond and a part of SP2 bond of carbon; Its film hardness is very high, but lower than that of diamond film; Its thickness is also thinner than the diamond film we usually deposit. When machining graphite, the service life 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 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 consistency of processing.
Processing hardened steel
Diamond is composed of carbon atoms. When some materials are heated, carbon atoms will be absorbed from the diamond and carbides will be formed in the workpiece. Iron is one of these materials. When diamond tools are used to process ferroelectric materials, the heat generated by friction will diffuse the carbon atoms in the diamond into the iron, which will lead to the premature failure of the diamond coating due to chemical wear.
Tool limits
It is difficult to guarantee the quality of diamond coated tools with heavy grinding and / or heavy coating. Because the coating on the surface of the tool is pure diamond, it takes a long time to regrind the tool with diamond grinding wheel. In addition, a tool used for growing diamond. The preparation process will change the chemical characteristics of the tool surface. Because the chemical characteristics are required to be controlled very accurately during coating, it is difficult to ensure the effect of tool re coating.
Tool life
Like any other tool, the life of diamond coated tool is different, which mainly depends on the material to be cut, the feed rate and cutting speed selected, and the geometry of the workpiece. In general, the life of diamond coated tools for processing graphite is 10-20 times longer than that of uncoated cemented carbide tools, and may even be longer in some cases. In this way, almost any machining task can be completed with one tool, without changing the tool due to tool wear, avoiding machining interruption and recalibration, and it is possible to realize unattended machining. In the processing of composite materials, it is also possible to obtain a long tool life.
It is reported that the life of diamond coated tools can be up to 70 times as long as that of uncoated cemented carbide tools when processing high-density glass fiber, carbon fiber and gl0-fr4 and other difficult to process composite materials.
Existing problems
The peeling off of diamond coating can prevent the peeling off of coating. It is a serious problem of diamond coated tools and a common problem (especially when processing carbon fiber and other materials), which will lead to the life of the tool difficult to predict. In the late 1990s, the interfacial chemical characteristics were identified as an important factor affecting the adhesion of diamond coatings. It is possible to reduce or eliminate the spalling of diamond coating and realize stable wear mode by selecting the chemical properties of cemented carbide with good compatibility, adopting appropriate pretreatment technology and reasonable deposition reaction conditions. By observing the diamond coated tool with normal wear under the microscope, it can be found that the diamond is stably worn until the cemented carbide matrix, and there is no edge collapse or peeling.
