What is Cermet?
The word cermet is a contraction of “ceramic” and “metal”. Cermet consists of a ceramic material (such as titanium carbide or titanium carbonitride) cemented with a metal binder. The ceramic provides the wear resistance, while the metal provides the toughness. This combination is more chemically inert than tungsten carbide and means that edge buildup and crater wear are much less likely compared to cemented carbide.
Looking at the chart below, it shows the comparison of cermet over coated carbide and carbide. Coated cermet is also available, which can extend the tools cutting life even further.
Cermet Advantages vs. Cemented Carbide
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Improved tool life
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Lower micro finish
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Higher cutting speeds
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High dimensional stability, able to achieve tight tolerances
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Minimal edge buildup, even with MQL
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Reduced crater and flank wear
Common materials that cermet performs well in include carbon steel, alloy steel and tool steels. In addition to this, cermet has proven to perform well with gray cast iron, ductile iron, powdered metals, non-ferrous alloys and even some non-metals.
Cermet Limitations
Nickel is a common binder material for cermet. This creates the potential for a chemical reaction if the workpiece also has a high nickel content. High temperature alloys and some stainless steels are among the nickel containing materials that can cause issues when using uncoated cermet tooling. To overcome this issue, the use of coated cermet has become popular when machining stainless steel and other nickel containing materials and has proven to be very effective.
Cast aluminum has also shown to be problematic. The issue here is mechanical instead of chemical in the fact that a high silicon content in aluminum tends to have an abrasive effect that can compromise the ability of the cermet to produce a smooth finish. PCD (polycrystalline diamond) is still preferred over cermet for machining aluminum since it can handle the abrasive nature of silicon.
Additionally
Micro grain cermet is capable of handling interruptions in parts that were not previously able to be machined with cermet. Advances in different binder material and processing have made it possible to produce different hardness and toughness of materials, allowing a range to find the best suited material for the application. Cermet tends to excel at higher cutting speeds (500 SFM) but with the correct grades and geometry of the cutting edge, it is capable of running at slower speeds (250 SFM) allowing for older machines geared towards traditional cutting speeds.
Cermet, if applied correctly to the application, can be used to help achieve an extremely efficient process, providing the best tool life and finish in a tight tolerance feature. Interruptions and uneven breakout or uneven entry to a feature are not limiting factors for cermet and these conditions can be overcome with success.