X Marks Aerospace Machining Solutions

With the demand red-hot for aerospace machining capability and capacity, chances are you'll need to learn how to machine titanium and high-temperature-resistant, nickel-based alloys more effectively. If you don't know the material's specific machining requirements, "you could be left out in the cold very easily," says John Palmer, Aerospace Market Manager for ATI Stellram.

"For example, one aerospace contractor had a 700 series nickel-based, high-temperature alloy to machine. The workpiece destroyed all of his tools just trying to machine the first piece. The company sent the work back because it would have been too costly to continue," he says.

ATI Stellram has improved the density of its cutting tool substrates and developed new coating technologies to manage the heat that is generated when machining aerospace alloys.

By using the right tools and machining approach, aerospace materials become relatively easy to machine. Following a few simple procedures and utilizing tooling applications from ATI Stellram, this company was able to successfully manufacture the part, and secure a valuable contract to produce high-temperature-resistant components.

ATI Stellram is a business unit of ATI Metalworking Products, an operating company of Allegheny Technologies Incorporated. They produce specialty metals, including titanium and titanium alloys; nickel-based alloys and superalloys; and stainless and other specialty metals

"‘Difficult-to-machine' isn't an absolute term, but a relative one," says Tom Hofmann, Global Product Milling Manager for ATI Stellram. "If you've only machined aluminium, then stainless steel is difficult. Moving upstream, nickel-based alloys and titanium alloys are more difficult. But, if you use the right combination of cutting tools, speeds and feeds, you can get effective production rates."

TITANIUM IS KING

The growth of titanium alloys in aerospace applications is outstripping that of nickel-based alloys. That's because titanium alloys are not only used in engine applications, where the growth of the two material families will be parallel, but are also used in airframe structures.

With the increasing use of composites in airframes, the overall use of titanium, which bonds to the composites better than aluminum, is growing exponentially. According to the US Geological Survey, about 79% of the titanium mill products shipped in the first quarter of 2006 were for commercial and military aerospace applications. Industry sources believe that titanium alloy consumption by the aerospace industry – both commercial and military – could nearly triple over the next decade.

Allegheny Technologies recently signed a $2.5 billion titanium products supply contract with The Boeing Company for commercial aerospace applications.

There's a synergy that exists between ATI Stellram and the Allegheny Technologies family of companies. Metallurgists and metal-cutting engineers from these companies pool their talents to develop machining solutions for the specialty metals that ATI produces.

By knowing the inherent structures of the materials, ATI Stellram is able to engineer exclusive formulations for cutting tool substrates. One result is X-Grade technology-a highly productive solution for machining such difficult materials as titanium alloys, nickel-based alloys and stainless steels, among others.

X-GRADE SOLUTIONS

X-Grade Technology Inserts provide a highly productive solution for machining such difficult materials as titanium, nickelbased alloys and hardened steels.

X-Grade technology utilizes a ruthenium/ cobalt alloy insert substrate, which results in thermal cracking resistance and propagation resistance, and allows higher metal removal rates. This proprietary substrate creates a stronger bonding matrix, thereby generating improved edge toughness. Coupling this with new geometries and coatings produces a combination ideal for machining aerospace alloys. Typical results for X-Grade Technology inserts include:

• Doubling the metal removal rate
• Tripling tool life
• Improving surface finishes

X-Grade Technology is available in three insert grades-X400, X500 and X700, each designed to meet specific difficult-to-machine available in standard insert styles, and many will fit the pockets of cutters that users may have on hand.

However, the best solution would be to use cutters that are specifically designed to optimize the performance of X-Grade Technology inserts. "Heat is the most significant factor when machining aerospace materials," Palmer says. "With aerospace alloys, you have to respect the radial and axial engagement of the tool, and more importantly, the time the tool has to cool down between exiting the cut and re-entering the material. If you don't apply this knowledge, particularly when machining titanium alloys and high temperature nickel-based alloys, surface speeds and metal removal rates will be very low and tool life will be poor."

In response, ATI Stellram has designed a series of cutters specifically to machine these materials, featuring innovative flute designs for maximum chip evacuation, reinforced pockets and maximized cooling. Two such advanced cutters are:

• 7710VRD Anti Rotation Button Cutter. The design of this innovative cutter features a free cutting geometry that allows dramatic increases in depth of cut and metal removal in today's most difficult-to-machine materials. The 7710VRD features round inserts with a patented locking indexation system to prevent insert movement under heavy feed rates. Teamed with X-Grade inserts, the 7710VRD provides consistent, long running performance with documented productivity increases of 150%.
• 7792VXD and VXE High Feed Cutters. These cutters improve metal removal rates by as much as 100% when compared to results produced with conventional cutters. In addition to high feed face milling, the 7792VXD and VXE are capable of pocketing, slotting and plunging. Cutting forces are directed axially into the spindle, lessening spindle wear and improving stability. Both modern and older equipment can benefit from the adoption of this technology.

ASK & RECEIVE

The best source of information and capability for optimizing your aerospace machining process is the cutting tool manufacturer. Many, like ATI Stellram, have application specialists experienced in machining aerospace alloys.

They'll review your process, including machine capability, component rigidity, fixturing, coolant, tooling and machining strategy-all the factors need to be balanced for the best result.

Unless you carefully select the right cutting tool, the most effective machine tool and the appropriate machining strategy for aerospace alloys, you are certain to have a difficult-to-machine experience rather than a relatively easy one.