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Kennametal’s new SiAlON KYS40 ceramic grade and the overall design of the solid ceramic endmill now offers the most effective way to rough nickel-based high-temperature alloys.
“Cutting speeds on nickel-based superalloys can be up to 20 times higher compared to solid carbide end mills, and due to ceramic’s outstanding heat resistance and stronger cutting edges (negative rake), tool life can last five times longer or more,” says Thilo Mueller, global product manager at Kennametal.
Two types of KYS40 solid ceramic end mills are available, a six-fluted version for face milling and profiling; and a 4-fluted, necked version for slot milling and pocketing. Both product lines allow ramping, helical interpolation, and trochoidal machining strategies as well.
The wear mechanisms and wear indication on the solid ceramic end mills is completely different from carbide, allowing running ceramic end mills far beyond the point where carbide tooling would need to be replaced. That’s also the reason that this new KYS40 grade end mill is a throw-away type of tooling to allow usage beyond regular type of wear.
Turbine Blade Machining
Whether powered by fossil fuels, hydro, or nuclear power, almost all electrical power on earth is generated by a turbine of some type. Producing, managing, and maintaining these critical components are vital to keeping the power flowing.
This puts a lot of pressure on manufacturers to continually update their machining strategies. Many factors affect this: Are large numbers of similar blades required or small volumes of different blade designs? Are multiple setups and machining centers involved or single multi-axis multitasking machines? What is the CAD/CAM system being used and what is the expertise of the operators?
And, of course, what are the best tooling choices for the machining operations? Recent test results involving the new KYS40 solid ceramic end mill are insightful.
First of all, the KYS40 Beyond grade ceramic in both the 4-flute and 6-flute versions features an enlarged core design that improves tool rigidity and reduces deflection at high cutting speeds. Optimized end geometry and a 40° helix angle increase shearing action and chip evacuation.
In roughing the profile of a small turbine blade made of Inconel 718, machined dry, the EADE 4-flute end mill was run at 645m/min (2116SFM), fed at 0.03mm/z (0.0012IPT). Depth of cut (ap) was 0.5mm (0.0197") and width of cut (ae) was 11.4mm (0.866"). Compared to a conventional solution, the EADE 4-flute mill lasted three times longer doing the roughing in less time. This application resulted in three times more parts being produced per mill.
The 6-flute EADE solid ceramic end mill was tested profiling a blisk (blade integrated disk) made of Inconel 718 and run with compressed air for chip evacuation. Unlike conventional carbide tooling, roughing to near net shape creates chips closer to dust than traditional curled chips, requiring only compressed air to blow them out of the cut. Test conditions were cutting speed of 679m/minute (2228SFM), feed of 0.03mm/z (0.0012 IPT), and the depth of cut varied up to 0.5mm (0.0197").
The results were two blisk segments machined with one tool at a 12-minute machining time per segment, which test personnel deemed “unprecedented.”