Testing Hyper-Carbide limits

Author Alan Richter
Published
December 01,2010 - 11:00am

Related Glossary Terms

  • Vickers hardness number ( HV)

    Vickers hardness number ( HV)

    Number related to the applied load and surface area of the permanent impression made by a square-based pyramidal diamond indenter having included face angles of 136º. The Vickers hardness number is a ratio of the applied load in kgf, multiplied by 1.8544, and divided by the length of diagonal squared.

  • alloys

    alloys

    Substances having metallic properties and being composed of two or more chemical elements of which at least one is a metal.

  • compacted graphite iron

    compacted graphite iron

    Cast iron having a graphite shape intermediate between the flake form typical of gray cast iron and the spherical form of fully spherulitic ductile cast iron. Also known as CG iron, CGI or vermicular iron, it is produced in a manner similar to that of ductile cast iron but using a technique that inhibits the formation of fully spherulitic graphite nodules.

  • coolant

    coolant

    Fluid that reduces temperature buildup at the tool/workpiece interface during machining. Normally takes the form of a liquid such as soluble or chemical mixtures (semisynthetic, synthetic) but can be pressurized air or other gas. Because of water’s ability to absorb great quantities of heat, it is widely used as a coolant and vehicle for various cutting compounds, with the water-to-compound ratio varying with the machining task. See cutting fluid; semisynthetic cutting fluid; soluble-oil cutting fluid; synthetic cutting fluid.

  • cutting speed

    cutting speed

    Tangential velocity on the surface of the tool or workpiece at the cutting interface. The formula for cutting speed (sfm) is tool diameter 5 0.26 5 spindle speed (rpm). The formula for feed per tooth (fpt) is table feed (ipm)/number of flutes/spindle speed (rpm). The formula for spindle speed (rpm) is cutting speed (sfm) 5 3.82/tool diameter. The formula for table feed (ipm) is feed per tooth (ftp) 5 number of tool flutes 5 spindle speed (rpm).

  • edge preparation

    edge preparation

    Conditioning of the cutting edge, such as a honing or chamfering, to make it stronger and less susceptible to chipping. A chamfer is a bevel on the tool’s cutting edge; the angle is measured from the cutting face downward and generally varies from 25° to 45°. Honing is the process of rounding or blunting the cutting edge with abrasives, either manually or mechanically.

  • feed

    feed

    Rate of change of position of the tool as a whole, relative to the workpiece while cutting.

  • hardness

    hardness

    Hardness is a measure of the resistance of a material to surface indentation or abrasion. There is no absolute scale for hardness. In order to express hardness quantitatively, each type of test has its own scale, which defines hardness. Indentation hardness obtained through static methods is measured by Brinell, Rockwell, Vickers and Knoop tests. Hardness without indentation is measured by a dynamic method, known as the Scleroscope test.

  • high-speed steels ( HSS)

    high-speed steels ( HSS)

    Available in two major types: tungsten high-speed steels (designated by letter T having tungsten as the principal alloying element) and molybdenum high-speed steels (designated by letter M having molybdenum as the principal alloying element). The type T high-speed steels containing cobalt have higher wear resistance and greater red (hot) hardness, withstanding cutting temperature up to 1,100º F (590º C). The type T steels are used to fabricate metalcutting tools (milling cutters, drills, reamers and taps), woodworking tools, various types of punches and dies, ball and roller bearings. The type M steels are used for cutting tools and various types of dies.

  • polycrystalline cubic boron nitride ( PCBN)

    polycrystalline cubic boron nitride ( PCBN)

    Cutting tool material consisting of polycrystalline cubic boron nitride with a metallic or ceramic binder. PCBN is available either as a tip brazed to a carbide insert carrier or as a solid insert. Primarily used for cutting hardened ferrous alloys.

  • polycrystalline diamond ( PCD)

    polycrystalline diamond ( PCD)

    Cutting tool material consisting of natural or synthetic diamond crystals bonded together under high pressure at elevated temperatures. PCD is available as a tip brazed to a carbide insert carrier. Used for machining nonferrous alloys and nonmetallic materials at high cutting speeds.

  • turning

    turning

    Workpiece is held in a chuck, mounted on a face plate or secured between centers and rotated while a cutting tool, normally a single-point tool, is fed into it along its periphery or across its end or face. Takes the form of straight turning (cutting along the periphery of the workpiece); taper turning (creating a taper); step turning (turning different-size diameters on the same work); chamfering (beveling an edge or shoulder); facing (cutting on an end); turning threads (usually external but can be internal); roughing (high-volume metal removal); and finishing (final light cuts). Performed on lathes, turning centers, chucking machines, automatic screw machines and similar machines.

  • web

    web

    On a rotating tool, the portion of the tool body that joins the lands. Web is thicker at the shank end, relative to the point end, providing maximum torsional strength.

When SRL Nano Corp. developed carbide-grade tools that use a patented binder material with a melting threshold similar to that of carbide—about 2,870º C—naturally the Rosemead, Calif., company dubbed the new material Hyper-Carbide. And once you view the video below that captures a series of cutting tool tests, it's easy to see why.

By comparison, carbide tools that use cobalt as the binder melt at about 1,495º C because that is the heat threshold for cobalt. And at 2,000 HV and harder, Hyper-Carbide is about three times harder than cobalt binder-style carbide. That makes Hyper-Carbide tools suitable for machining hardened steels, hardened high-temperature alloys, compacted graphite iron and even carbide, according to SRL. 


Scott Gore, a technical support specialist with Setech Inc., Murfreesboro, Tenn., provides the commentary for a series of Hyper-Carbide cutting tool tests captured on video. Presented as a Web-based supplement to an Industry News item in Cutting Tool Engineering's December 2010 issue, the brief report includes video supplied by Setech and SRL Nano Corp., a California company specializing in high-strength cutting materials.

The hardness of the material, however, also makes it more brittle than other carbide grades, so obtaining sufficient corner strength on a cutting tool is difficult. SRL said Hyper-Carbide is tougher than cemented carbide when both materials have the same hardness, and the average tranverse rupture strength of one Hyper-Carbide grade is 700 ksi.

SRL experimented with applying K-lands and other edge preparations to the cutting edges, but obtained inconsistent results, noted Scott Gore, who works with SRL on testing applications. "Tools live and die with their corner strength," he said.

For a solution to this problem, SRL turned to Conicity Technologies, a manufacturer of equipment for creating edge preparations on cutting tools. The Greensburg, Pa., company initially treated the Hyper-Carbide tools like conventional carbide but then changed the parameters to those more typical for edge prepping PCBN and PCD tools, noted Bill R. Shaffer, Conicity's executive vice president. "I actually have to run the equipment at settings that would destroy both PCBN and PCD, and what I got was a beautifully controlled prep," he said. "The tool material immediately responded to the increased corner strength."

Shaffer explained that he applies a 0.0012" waterfall, or oval, edge preparation to direct cutting forces at 15º to 20º angle into the tool. That edge prep reportedly increases corner strength six to 10 times.

With its corner-strengthened tools, SRL began conducting tests earlier in the year and generated postive results. For example, in a test conducted Sept. 23 at Weartech International Inc., Santa Fe Springs, Calif., a 3"-dia. Stellite 6 casting with a hardness of 46 HRC was turned with a grade-SK11 Hyper-Carbide CNG332 insert at a cutting speed of 600 sfm, a 0.004-ipr feed rate and a 0.010" DOC when dry machining, and when a water-soluble coolant was applied.

According to SRL, the insert showed no wear after a 10" length of cut. In contrast, Weartech previously applied a grade-907 CNG4321t carbide insert at 100 sfm, 0.005 ipr and a 0.010" DOC with coolant, and a grade-670 CNG4321t ceramic insert reinforced with silicon-carbide whiskers at 250 sfm, 0.004 ipr and a 0.010" DOC with coolant. These inserts exhibited wear after the same length of cut.

In another test the same day at Accufab Inc., Ontario, Calif., SRL compared its grade-SP17 SNG432 insert to a PCBN insert when turning a 1:-dia., M-2 HSS workpiece hardened to 64 HRC for a 1.25" length of cut. The PCBN tool ran at a cutting speed of 150 to 300 sfm, a feed of 0.002 ipr and a DOC less than 0.020" with coolant. SRL's insert was able to dry turn the material at up to 1,000 sfm, a 0.002-ipr feed and a 0.080" DOC.

Although all the tests have been conducted for continuous cutting, the company plans to do interrupted-cutting tests. Also, the company performed the tests with uncoated tools, but the tool material can be coated with commercially available coatings.

SRL plans to offer its tool material for commercial industrial applications in 2011. For more information, visit the company's Web site for its new material: www.hypercarbide.com.

Author

Editor-at-large

Alan holds a bachelor’s degree in journalism from Southern Illinois University Carbondale. Including his 20 years at CTE, Alan has more than 30 years of trade journalism experience.