Inconel is a great example of a high-performance metal specifically formulated for some of the most rigorous applications. Since it is often more expensive and less widely used, Inconel is generally less familiar than steel or aluminum. This article will provide some basics about Inconel and provide answers to some common questions about this unique metal.
Inconel is the name for a group of nickel-based superalloys. The name Inconel is a registered trademark of Special Metals Corporation out of New Hartford, New York. The company acquired the name through acquisitions of previous companies that originally developed the various Inconel alloys. The first Inconel alloys were originally formulated for demanding, high-temperature environments in the middle of the 20th century.
Since Inconel is a group of superalloys and not just one type of superalloy, its chemical composition varies across the different alloy types. However, all alloys in the Inconel family are nickel-based. Additionally, chromium is typically the second most abundant element in the chemical makeup of Inconel. Virtually every Inconel has some amount of iron in its composition, almost always greater than 1%. Other elements that are found in some Inconel alloys include:
The combination of physical and chemical properties that Inconel possesses are what make it so special. Inconel is known for its ability to withstand incredibly high temperatures. While materials like steel have a higher melting temperature than nickel, their performance in terms of strength and corrosion resistance begins to deteriorate at elevated temperatures. Inconel, on the other hand, maintains excellent strength properties at high temperatures and forms a protective oxide layer that resists corrosion at high temperatures.
In addition to high temperature performance, Inconel has excellent strength properties at room temperature. The high amounts of chromium also give it superb corrosion resistance at room temperatures as well. The other alloys mentioned above in the composition section provide additional properties such as toughness and hardness. Several Inconel alloys, such as Inconel 718, are precipitation hardened to increase strength even further.
Inconel is used in many different industries. One of the most common applications for Inconel is in the aerospace industry, namely in the high-temperature environment found within the jet engine. Fuel nozzles, afterburner rings, and other engine components are commonly made out of Inconel. This is because they perform well in the elevated temperature found during operation. They also resist the risk of corrosion presented by jet fuel and other liquids. Inconel is also often used in rockets and space exploration vessels. Common alloys in the aerospace industry include Inconel 625 and Inconel 718.
Another common use of Inconel superalloys is in the nuclear industry. Nuclear reactors require high strength, high corrosion resistance, and excellent elevated temperature performance, which is why Inconel is frequently used. Common alloys in the nuclear industry include Inconel 600 and Inconel 690.
Other industries that use Inconel less frequently include automotive, manufacturing equipment/tools, oil & gas, firearms, and several others. Any application that requires high strength and high corrosion resistance in an elevated temperature environment is typically a good candidate for Inconel use.
References:
INCONEL alloy 625 (specialmetals.com)
Inconel alloy 718 (Sept 07) Web.qxd (specialmetals.com)
The Invention and Definition of Alloy 625 (tms.org)
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