meaning all of the Inconel 718, Renes, and Waspaloys etc. We have to plan the kind of tooling materials that will be need- ed. Titanium aluminide is abrasive, stiff, tough, and doesn’t conduct heat. Its machinability rating is very low. For example, if you made one part out of soft steel and it took one tool to make a part; it would take 20 tools to machine the part out of titanium aluminide, compared with 6 to 7 tools to machine the part from Inconel 718,” said Graham.
Preferred Orientation of Crystals
“When a customer has a problem, we look at the wear mode and our stable of technology solutions,” said Kurt Ludeking, product manager-turning, Walter USA LLC (Wauke- sha, WI). “We use a lot more micrograin substrates for their balance of toughness and hardness due to resistance to deformation. The primary role for coatings is wear resistance, but coatings also play an important role in edge toughness. Through careful design of the coating system, the substrate, and post-coating processes, edge toughness has been
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increased significantly with our Tiger-tec Silver turning inserts for steel,” said Ludeking.
“For steel turning, we’ve changed the aluminum oxide coating to include preferred orientation of the crystals which significantly improves crater wear resistance and heat resis- tance that can lead to deformation of the cutting edge. Any time you have heavy depth of cut or interrupted cuts espe- cially, chipping of the coating is a big issue. By changing the technology that we apply to the coating and the post treatment that we do, we’ve been able to increase compressive stresses and increase the chipping resistance on these new inserts,” said Ludeking. “I’m talking turning here, but this technol- ogy was first implemented in milling. We’ve used the same preferred orientation technology, the blasting process, and the edge geometry in milling to improve our results, achieving gains of 30–40% in tool life and 15–30% increases in speed.” While the coating and substrate have the largest impact on tool life and application area, the edge geometry and form of the chip-breaking features are also critical. “By optimizing the edge geometry and chip flow through the chip breaking area, Walter Valenite has made additional improvements in tool life for a variety of applications,” said Ludeking. “Examples include Tiger-tec Silver Turning for steel, high-temperature alloy NMS/NRS geometries with PVD Al2O3. New coatings technologies in both CVD and PVD have extended tool life sig- nificantly. For PVD coatings, this has also extended their use into new areas such as milling hardened steels and grooving in cast iron with grades WHH15 Tiger-tec Silver PVD. “Uncoated inserts are used mainly for nonferrous applica- tions such as aluminum, brass, and softer alloys, though not as much for stainless steels anymore,” said Ludeking. “Un- coated inserts are really for those applications that require a very sharp edge. Whenever you use a coating, you can’t make the edge super sharp. Coatings just don’t stick to it, and also carbide polishes better than a coating and polished carbide works better for aluminum, brass, and sticky alloys.”
Drilling Process has its Own Parameters In the case of drilling, it’s important to understand the process to be able to design appropriate tools. “An example of this is drilling. While the coating is important for wear re- sistance in the cutting zone, it isn’t helpful in the drill flutes,” said Ludeking. “Even the smoothest coating is rough enough to create additional friction and slow down chip flow, which is especially important in difficult-to-machine materials. By