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C&A Tool, the Superpower of Superalloys

Category: IMTS Network Jun 4, 2021

C&A Tool in Churubusco, Indiana, operates more than 200 CNC machines to make parts for the aerospace, medical, and industrial sectors.

This article explores superalloys and Inconel® in more detail as they are such an important part of machining parts for the aerospace industry.

As you might remember from chemistry class, an alloy is a combination of a metal with at least one other metal or nonmetal. Alloys are developed because they have enhanced mechanical or chemical properties, such as hardness, strength, corrosion resistance, heat resistance, and others, and in the metalworking industry, they are more common than metals. Chromium, tungsten, lead, magnesium, copper, nickel, silicon, and carbon are some of the many elements added to impart desired characteristics.

A subcategory of alloys, superalloys – also called high-temperature alloys – share properties of high-temperature corrosion resistance, oxidation resistance, and creep resistance. They fall into three main categories: nickel-based, cobalt-based, and iron-nickel-based alloys (which also include titanium alloys).

Nickel-based alloys are the most widely used in the manufacturing industry, and their properties are especially critical in the aerospace industry, where they are widely used in engine and power generation turbine components.

Superalloy Inconel is the trade name for a group of more than 20 metal alloys made by Special Metals Corp. and is used for some of the toughest environmental conditions. Inconel 718 is the workhorse of superalloys. Introduced in 1965 at industrial scale, it is the predominant superalloy used in industry today and accounts for up to 50% of the weight of aircraft turbojet engines. It is also widely used for other aerospace components due to its high strength-to-weight ratio, incredibly high tolerance for extreme heat, and resistance to oxidation and corrosion. It is also used in combustors, turbocharger rotors and seals, heat exchangers, and nuclear reactors. It is expensive, so it is used when other materials will not work as well.

Machining Superalloys
Despite their valuable properties, there are several key challenges to machining nickel-based superalloys such as Inconel. The very characteristics that provide superior high-temperature strength also make them difficult to machine. The most common challenges include:

  • Their low thermal conductivity means that heat produced during machining is transferred to the tool, thus increasing the temperatures of tool tip and causing excessive tool wear.
  • Their high strength at cutting temperatures causes high cutting forces, which also generates heat at the tool tip and limits their speed capability.
  • Hard, abrasive intermetallic compounds and carbides in superalloys cause severe abrasive wear on the tool tip.
  • They have the tendency to work harden at the surface and generate heat, causing depth-of-cut notching on the tool, which can lead to burr formation on the workpiece.

The optimal way to machine a given superalloy further depends on the type of tooling being used – carbide tooling, ceramic tooling, or PCBN tooling.

Superalloys are not for the inexperienced machine shop; however, due to the high demand for these materials by some of the largest OEMs in the manufacturing industry, it is well worth exploring market opportunities and making the investment in the equipment needed to machine them.

Watch this video to join AMT Vice President and Chief Revenue Officer Travis Egan and his son Max as they visit C&A Tool and see engine turbine components machined from superalloy Inconel®; climb into CNC machines so large that half a dozen people can fit inside them; and learn about small navigated neurosurgery parts. (AMT – The Association For Manufacturing Technology owns and operates IMTS – The International Manufacturing Technology Show.

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