Small Scale Thinking
Small-Scale Thinking: Tool Supplier's Perspective
September 27, 2010
By Jim Destephani, Senior Editor, Cutting Tool Engineering
Cutting tool suppliers and coaters have known for years that multilayer structures are stronger and more wear-resistant than monolayers. Carrying that idea into the nano realm are small-diameter endmills and drills manufactured by Harvey Tool Co. LLC, Rowley, Mass.
“Multilayers work to control crack initiation, and if there is any cracking or flaking it takes much longer to propagate
through the entire coating structure,” said Jeff Davis, vice president of engineering for Harvey Tool.
Harvey Tool’s nanolayer coatings typically are 1μm to 4μm thick, compared with 2μm to 5μm or more for its conventional AlTiN material. Davis said the smaller crystal size of the nanocoating material enables production of a thinner coating layer with a more cohesive and uniform structure. “The nano part comes in when you‘re putting on very thin layers of AlTiN, and the smaller the crystals, the more cohesive and uniform the structure.”
According to Davis, the result of nanocrystalline deposition is higher hardness and heat resistance. Harvey Tool claims hardness of 45 GPa and maximum working temperature of 2,100° F for its nano AlTiN material, compared to 35.5 GPa and 1,400° F for its conventional AlTiN grades.
Those improved properties translate to tools that can last longer than conventionally coated tools in difficult applications, Davis said. “Probably the single best application is milling of hardened steels—materials starting at about 45 HRC and climbing to the top of the Rockwell C scale. Traditional TiN is not going to work there. AlTiN is a step in the right direction, but nanocoatings, coupled with the right edge prep, substrate and geometry, enable users to improve tool life from maybe seconds to minutes.”
Davis said his company sees future applications for nanocoatings in drilling as well. “If you’re making holes more than maybe 4 diameters deep, getting coolant down to the tool tip is always a critical issue. You can peck or do other things, but the ability of these coatings to take more heat would be beneficial in that kind of application.”
Still, Davis advises caution when applying tools with nanocoatings. “These coatings are not like TiN, where you put it on just about anything and you’ll see improved performance,” he said. “They are application-specific, and the field in which you use them is fairly narrow. We use them on hard milling tools, a couple of finishing tools and some variable-helix tools. And again, it’s not just the coating— it’s the edge prep, the substrate, relief and helix angles, core diameters— all these things come together to make tools live in very difficult applications.”
Read the entire article at ctemag.com >>