Superalloys have changed the world we live it. From high speed jets to state of the art medical devices our lives are made better by these materials and the fasteners used to hold them together.
What are they: Superalloys are combinations of elemental metals that 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 minuscule amounts.
History: It is a paradox that some of the greatest medical advances in history are a result of war, with its technological advances often turning into civilian and peacetime innovations. The experimentation and innovation with superalloys was in large part driven by military and aerospace needs in the twentieth century.
Commercially viable stainless steel was developed in the early 1900's. However, when stainless steel was found to be limited in its strength, high temperature performance, and corrosion-resistant capabilities, scientists began experimenting with alloys. The resulting iron-base materials were soon dubbed superalloys.
With high operating temperatures and extreme stress conditions, aircraft provided an unparalleled testing ground for specialty materials and fasteners. There was explosive development in the field from 1940 to 1960 with many of the superalloys in use today coming into mainstream use at that time. It did not 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.
Superalloys fall into three basic groups: Iron -nickel-base, nickel-base, and the cobalt-base superalloys make up the main types. 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 high temperatures – just below their melting temperatures of about 2200 to 2500 degrees Fahrenheit. Iron-nickel-base superalloys can be used at temperatures up to 1300 degrees Fahrenheit but are less expensive. High temperatures aside, cryogenic applications and body temperature applications (eg medical prosthesis), also exist.
Popular superalloys:
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. Typical fasteners in A286 include socket heads, hex heads and 12 point.
Inconel is a nickel-base superalloy, making it suitable for very high temperatures, extreme environments, and demanding applications. Typical 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 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. Typical fasteners in Monel 400, Monel 405, and Monel K-500, including flat sockets, flat washers, hex heads and nuts, and machine screws.
MP35N is a nonmagnetic nickel-cobalt superalloy . It features high fatigue and high strength properties and has excellent environmental resistance. It is commonly used in medical devices, food processing, chemical, and marine environments.
Invar 36 is an iron-nickel-base alloy. It is a controlled expansion alloy and commonly used in electronic equipment. Typical fasteners made out of Invar 36 include CNC machine parts, machine screws, and dowel pins.