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An Introduction to Superalloys

It is a paradox that war is responsible for some of the greatest medical advances in history. By the same token, technological advances necessitated by war often turn into civilian and peacetime innovations. A good example of this is the superalloys.

After the development of commercially viable stainless steel at the turn of the twentieth century, metallurgists continued to push the envelope in the search for stronger, more corrosion-resistant material for high-temperature applications. When stainless steel was found to be limited in its strength capabilities, they began experimenting with alloys. These improved iron-base materials were soon dubbed superalloys.

Superalloys display excellent mechanical strength and creep resistance at temperatures above 1000 degrees Fahrenheit, good surface stability, and corrosion and oxidation resistance. This is achieved by adding other elements to the base, including nickel, cobalt, chromium, aluminum, tungsten, and molybdenum, among others. Some of these elements are added in large amounts, some in small, even miniscule amounts.

This experimentation was driven in large part, of course, by military and aerospace needs in the twentieth century. The high operating temperature and stress conditions of aircraft provided an unparalleled testing ground; the gas turbine engine used in aircraft has essentially been made possible by the development of superalloys. There was explosive development in the field from 1940 to 1960 -- by the mid ‘60s, many of the superalloys in use today were already in existence.

It didn’t take long for these amazing new materials, perfected in wartime, to find their way into peacetime applications. Although the aerospace industry is still the biggest consumer of superalloys, the medical field, the food processing industry, the energy industries, and the semiconductor industry all have a need for superalloys and superalloy fasteners.

The superalloys fall into three basic groups: the iron-nickel-base superalloys; the nickel-base superalloys; and the cobalt-base superalloys. The iron-nickel-base superalloys evolved from stainless steel technology and are generally wrought. Nickel-base and cobalt-base superalloys can be either wrought or cast. Nickel-base superalloys can be used at the very highest temperatures, just below their melting temperatures of about 2200 to 2500 degrees Fahrenheit. However, iron-nickel-base superalloys are less expensive and can be used at temperatures up to 1300 degrees Fahrenheit. Although all of the superalloys were developed for use at high temperatures, some are used for cryogenic applications, and others at body temperature for medical prosthesis applications.

OSS offers fasteners made from these superalloys:

A286

Alloy A286 is one of the most commonly used iron-nickel-base superalloys. It offers high strength and corrosion resistance at temperatures up to 1300 degrees Fahrenheit (704 degrees Celsius). Frequently used in the aerospace industry, it can be precipitation hardened to a strength level. One of our most requested materials, OSS offers a variety of fasteners in A286, including socket heads, hex heads and 12 point.

Inconel

Inconel is a nickel-base superalloy, making it suitable for very high temperatures, extreme environments, and demanding applications. OSS offers a wide variety of fasteners in Inconel 600, Inconel 601, Inconel 625, Inconel 718, and Inconel X-750, including 12 points, button sockets, dowel pins flat sockets, and threaded studs/double end studs.

Monel

Monel is a nickel-base superalloy. Its corrosion resistance makes it ideal for marine applications. It is also resistant to corrosion by acids and oxygen, making it a good material for the chemical industry. OSS offers a variety of fasteners in Monel 400, Monel 405, and Monel K-500, including flat sockets, flat washers, hex heads and nuts, and machine screws.

Invar 36

Invar 36 is an iron-nickel-base alloy. Because it is a controlled expansion alloy, Invar 36 is commonly used in electronic equipment. OSS has provided a variety of fasteners out of Invar 36, including CNC machine parts, machine screws and dowel pins.

More articles from OSS:

From Cutlery to Space Shuttles: The History of Stainless Steel and Superalloys

The History of the U.S. Fastener Industry

A Strong Family Tree: An Introduction to the Grades and Types of Stainless Steel

The ABC's of Nuts and Bolts

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