Machine shops have long turned to carbide as the first choice for cutting tools. Available in a wide range of grades and coatings, it provides a predictable blend of toughness, strength and wear resistance in everything from aluminum to heat-resistant superalloys.
But sometimes there’s a better mousetrap. Consider turning operations. For steel and cast-iron parts, most lathe operators would say, “No problem. I’ll take them over Inconel any day of the week.”
“When finishing steels, the combination of cermet’s chemical stability and high cutting speed potential tends to leave shinier, more attractive finishes compared with carbide.”
Brian Wilshire,
Senior Application Engineer,
KYOCERA Precision Tools
They might answer differently if asked to deliver a very fine surface finish on low-carbon steel shafts, for example, or crank out massive quantities of cast-iron rotors as quickly as possible. For these and other challenging operations, carbide can often take a back seat to an underutilized alternative: cermet.
What Is Cermet?
“Cermet is a composite cutting material built around a ceramic hard phase with a metallic binder,” explains Brian Wilshire, senior application engineer with KYOCERA Precision Tools.
For KYOCERA, this hard phase consists primarily of titanium carbide (TiC) and titanium carbonitride (TiCN), which provide hardness and wear resistance. Nickel is used as the main binder, with small amounts of cobalt added to improve bond strength and toughness.
This combination gives cermet a useful balance: ceramic-like hardness and wear resistance with greater toughness and fracture strength than conventional ceramic cutting materials, making it about three times stronger than alumina ceramics.
Cermet should therefore be viewed as a complementary cutting tool material rather than a universal replacement for carbide. Yes, carbide remains extremely versatile, particularly when toughness is the primary requirement. However, cermet becomes especially attractive in stable finishing and semi-finishing applications where the priorities are wear resistance, surface finish, dimensional consistency and the ability to run at higher cutting speeds.
Cermet vs. Carbide: Key Differences
Wilshire notes that one of the biggest differences between cermet and carbide is how the cutting edge interacts with the workpiece. In steel, cermet’s titanium-based hard phase has a lower affinity for the work material, which helps minimize built-up edge.
“When finishing steels, the combination of cermet’s chemical stability and high cutting speed potential tends to leave shinier, more attractive finishes compared with carbide,” he says.
The takeaway? A shop should not necessarily ask, “Can cermet replace our carbide?” The better question is, “Which operations are we currently using carbide for where we are paying for toughness we do not need?”
Those finishing operations can be good candidates for cermet.
Best Materials and Applications for Cermet
Wilshire describes the cutting material’s sweet spot: “Ideal applications for cermet are carbon and alloy steels and cast iron with depths of cut under .040 inch (1 millimeter) in clean, pre-machined workpieces under stable conditions.”
Tyler Martin, application engineer with KYOCERA Precision Tools, agrees. “Cermet is often at its best in stable finishing cuts on steel, where its wear resistance can help maintain surface finish and part size over a production run.”
Cermet can also work in other materials, Wilshire adds, but grade selection and application conditions become especially important. His rule of thumb: “Use carbide where toughness and stability are important, and use cermet where finish and size control are necessary.”
Key Benefits of Cermet
Cermet has several properties that make it particularly beneficial for certain jobs, but especially in stable, higher-speed finishing applications. These benefits include:
Superior Wear Resistance at High Speeds
Where the application allows it, cermet can maintain a consistent cutting edge at speeds that make it attractive compared with conventional carbide finishing grades. Potential productivity gains include longer useful edge life and, in the right application, the ability to increase cutting speed and reduce cycle time.
Smoother Surface Finishes
Martin suggests this is one of the clearest reasons to evaluate cermet. A clean, stable cutting edge produces a more consistent finish throughout the insert’s life. The cermet payoff is biggest when a shop changes out carbide inserts because the surface finish has deteriorated, not because the tool has reached its true wear limit.
Longer Tool Life in Finishing Passes
Tool life shouldn’t be measured simply by how long an insert remains physically intact, he adds—in a finishing operation, the more important question is often how long the insert continues producing an acceptable part. Martin cites one recent example, where a customer turning 17,000 cast-iron bushings annually was seeing 32 pieces per edge with their legacy VNMG332 carbide inserts.
“After switching to KYOCERA’s CCX cermet grade, tool life increased to 300 pieces, saving the shop more than $3,000 per year in tooling costs alone,” he says.
Lower Cost Per Part
Both experts agree that the insert’s purchase price is only one component of tooling cost, and that cost per finished component is the better comparison. These savings can come from several places:
More parts per edge
Higher cutting speeds and shorter cycle times
Fewer insert changes and less machine downtime
Lower scrap or rework associated with poor surface finish
Potential reduction or elimination of secondary finishing operations
Common Switching Mistakes to Avoid
The first mistake is treating cermet as a drop-in replacement for carbide without reconsidering the application. As Martin points out, the grade, geometry, edge preparation and cutting conditions all matter, which is why a shop that installs a cermet insert and simply runs the same parameters it used with carbide may never realize the potential benefit.
The second is putting cermet into an application that requires more toughness than it is designed to provide. Heavy interruption, unstable workholding, vibration, scale or inconsistent stock conditions may favor carbide. “Moving from carbide to cermet makes the most sense when a stable finishing cut is limited by wear or surface finish,” he says.
Sourcing the Right Cermet Grade
Wilshire cautions against treating cermet as a single cutting-tool grade. Just as carbide grades are engineered for different applications, cermet grades and geometries are designed around different combinations of wear resistance, toughness, finishing capability and cutting conditions.
“When replacing carbide with cermet, stick with one of our tougher cermet grades such as PV730 to prove out the process,” he recommends. “PV730 is the first choice, PV720 moves toward wear resistance, and CCX is the high-speed finishing option.”
The correct choice depends on the following factors:
Shops should work with the cutting-tool manufacturer and distributor to pick the right grade, Martin advises.
“This is an area where we can be especially helpful,” he says. “Rather than simply substituting a cermet insert for an existing carbide insert, the goal should be to identify the correct grade and geometry and then optimize the cutting parameters around it.”
Read more: How to Spend Less on Carbide: Proven Strategies from Tooling Experts
