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New Aerospace Materials Require New Cutting Tools

Ilene Wolff
By Ilene Wolff Contributing Editor, SME Media

In aerospace manufacturing, where high strength, light weight, and corrosion resistance are key material traits, those same qualities make materials hard to machine. In response, Greenleaf offers a new ceramic for cutting tools, Sandvik Coromant’s advice for machining new, complex titaniums is to go slow, and RobbJack has designed a drill specifically for CFRP composites.

On the cutting tool side, Greenleaf Corp. (Saegertown, PA) has a new phase-toughened ceramic, XSYTIN-1, for use with difficult-to-machine nickel-based and cobalt-based materials.

“It’s a different kind of ceramic altogether, and the first of its kind in the industry,” said Jan Andersson, global director of Greenleaf’s TechTeam and marketing. “The advantage is it’s incredibly strong. The transverse-rupture strength is much higher than whisker ceramics, and whisker ceramics are commonly known as the strongest ceramics in the market.”

XSYTIN-1 is particularly useful in aerospace because materials used to make jet engines have a high tensile strength that exert a high degree of stress on the microgeometry of the material they’re machined with. The new material is also thermally stable, which prevents thermal cycling and subsequent cracking during milling, Andersson said.

“Because XSYTIN-1 is so strong, it allows us to use a significantly higher feed rate than traditionally we would use with other ceramics,” he said. “That, in turn, means we can better manage our temperature and get a more predictable tool life that way.”

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Greenleaf’s new phase-toughened ceramic, XSYTIN-1, is thermally stable in the cut, which prevents thermal cycling and subsequent cracking during milling.

For structural components in aerospace, “I’ve been seeing a lot more of the complex titanium parts,” said William Durow, manager of the global engineering product office for Sandvik Coromant (Fair Lawn, NJ). Specifically, he mentioned Ti-1023, Ti-5553 and beta titanium, all of which have high strength, are lightweight and corrosion resistant—and are notoriously hard to machine.

“A lot of it is how you approach the components,” Durow said. “You need to watch your speeds and run it [slower] like nickel-based materials.” His recommendation is to mill complex titanium at 75–100 sfm [23–30 smm].

For use with CFRP-reinforced materials, RobbJack Corp. (Lincoln, CA) has a polycrystalline diamond, “W”-tipped drill.

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RobbJack’s polycrystalline diamond, “W”-tipped drill cuts clean holes on CFRP-reinforced materials, compared to the rough edges left by conventional cutting tools

“We’re able to flute diamond now like carbide using electrical discharge grinding,” said Mike MacArthur, vice president of engineering. “And that’s very new technology that’s allowed us to get all the advantages that you could grind in carbide but now in a solid piece of diamond.”

In the past, MacArthur explained, you either had to have a flat plane of diamond that was brazed into carbide or grind a path and then sinter diamond into a thin area of a tool.

“Now we can take a solid nib of 100% polycrystalline diamond and we can actually grind it like you would carbide,” he said.

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