Milling grade well suited for titanium and other superalloys

WIDIA Products Group´s Manager Portfolio Management for Turning and Indexable Milling, Josef Fellner, commented: “The company recently took its newest advanced milling grade, WS40PM, on a world-wide testing tour.” The results have been quite impressive:

• An aircraft manufacturer enjoyed a 90% reduction in machining time per piece and increased tool life by 50% during Ti-6Al-4V face milling operations.
• Insert flank wear decreased by more than 90% at a UK shop cutting Inconel 625, resulting in a 70% reduction in tooling costs.
• At a turbocharger producer in China, tool life increased 80% while machining an austenitic stainless steel component using WS40PM, with improved part surface quality, reduced cutting forces and better chip flow.
• In another titanium component, the WS40PM/VSM490-15 platform doubled metal removal rates and delivered 80% longer tool life through increased depth of cut and feed per tooth in face and shoulder milling operations.
• The testing laboratory for a well-known brand of machine tools reports metal removal rates 49% greater when shoulder milling Ti-6Al-4V.

In each instance, WS40PM competed with the test subject´s legacy carbide grade. Speeds and feeds were kept the same or in some cases increased to take advantage of WS40PM´s exceptional toughness, wear-resistance, and ability to resist thermal cracking.

WS40PM was designed to meet the needs of the aerospace, defence, and medical industries, where titanium is used for everything from landing gear and seat tracks to lifesaving implants and surgical instruments.

As the testing results show, however, WS40PM is suitable for far more than titanium. High-temp steel alloys, austenitic and PH stainless steels, nickel-based super alloys such as Hastelloy and Nitronic—these materials cause tool failure due to built-up edge (BUE), notching at the depth of cut line, cratering, chipping, and extreme heat generation, which in the case of wet-cutting operations leads to cracking.

Mike Sperhake, EMEA-region Product Specialist for WIDIA said: “WS40PM´s advanced cobalt-rich substrate provides robust fatigue resistance and edge integrity, while the multiphase AlTiN-TiN PVD coating reduces wear.”

Sperhake continued: “Using an initial cutting speed of 175ft/min (53m/min) we´re seeing 25-35% productivity gains and consistent improvement in tool life, even when milling very tough materials like Ti-5553 and Super Duplex steels.”

Sperhake recommends a balanced approach to cutting parameter selection. He added: “As radial engagement increases, cutting speeds should be reduced proportionately. That´s because the amount of heat entering the insert goes up substantially on heavy cuts, at around 90% engagement, for instance, you´ll probably want to reduce the RPM by 25% or so, depending on the material. Feedrates may also have to be lessened somewhat, depending on setup and machine rigidity. And smaller cut widths, of course, spindle speed and feedrates should be kicked up substantially.”

“Going too easy is a common mistake when machining titanium and other difficult materials, leading to poor productivity levels and shortened tool life. For example, problems such as BUE and edge wear can often be eliminated by pushing the tool harder. Tool life, especially in superalloys, is a three-legged stool of feed, speed, and cutter engagement. Each has a direct impact on the others,” Sperhake added.

Success with superalloys takes more than a good carbide grade, however. Sperhake also recommended increasing the cutting fluid concentration, and using a high-pressure coolant pump wherever possible. Selecting the right cutter body for the application is likewise important. WIDIA's VSM490 shoulder mill offers a state of the art insert and cutter design, one that supports WS40PM and other high-performance grades.

Finally, considering the machine tool, toolholder, and spindle interface, rigidity across the board is needed for productive titanium machining. WIDIA offers the KM4X platform.

Global Product Manager Bill Redman said: “The strongest connection available, period, and is available on a wide variety of toolholders and machine tools alike.”

Sperhake concluded: “From Tier 1 aerospace suppliers to the job shop on the corner, everyone wants the same things from a tooling solution: higher accuracy, better surface finish, reliability and productivity. All are critical factors to their success, and that´s what we intend to deliver. WS40PM is a big part of that.”