Dynamic Duo for Aerospace: Rough With Ceramic, Finish With Carbide

By Aaron-Michael Eller and Scott Causey of Seco Tools

  

The superalloys found in turbine blades, jet engines and other critical aerospace components are some of the most difficult-to-machine materials in manufacturing, a fact that has driven the development of advanced cutting tools and materials. However, strict regulations and the materials’ physical characteristics often require the use of standard processes performed with standard carbide. As a result, the aerospace industry can find itself caught between a regulatory rock and cost-effectiveness hard place – unless manufacturers use an approach that brings conventional and advanced tooling together in one process.

Everything from aluminum and boron to yttrium and zirconium can be found in superalloys, which are formulated specifically to maintain the structural integrity of aerospace components exposed to extreme temperatures. As a result, the optimal cutting tools for these materials are usually made of ceramics, which possess outstanding heat resistance that enables cycle times that are up to 10-15 times faster than carbide in turning applications. The round inserts often used for these applications also offer two to three times more cutting edges than the equivalent conventional solution and feature excellent tool life, making it ideal for the demanding aerospace market.

At the top speed of applications using ceramic inserts, however, enough heat is generated that the metal is essentially plasticized, a problem for aerospace components. Because flight-critical parts must meet stringent regulatory standards, the fact that advanced ceramic tooling creates heat-affected zones and a brittle white layer in the material necessitates a different approach for finishing. Instead, manufacturers simply stick with ceramics for roughing and switch to carbide for finishing. But when white layer formation itself isn’t an issue, Seco offers specific PCBN grades for nickel-based materials that can finish at speeds six to eight times faster than the equivalent carbide tool.

When parts absolutely must be finished with carbide, a requirement for working with some companies in the industry, manufacturers can still achieve superior results by pairing that carbide with Jetstream Tooling^®. When roughing with ceramics, air blasting is generally sufficient for chip control, but for the high tolerances and surface finish requirements for flight-critical components, high-pressure coolant is the best way to keep chips and temperature controlled for an optimally finished part.

Of course, in the fast-moving world of the aerospace industry, the next leap forward in materials science may only be a few years or months away. Already, carbon-fiber-reinforced polymers (CFRP) and powdered metals used for additive manufacturing processes are presenting new challenges for aerospace shops. To maximize productivity in the face of untested materials, turn to your tooling supplier, as Seco works closely with its customers as well as partners in the materials industry to find the cutting parameters, geometries, lead angles and grades that can achieve cost-effective results. Find out more at www.secotools.com.