Inconel

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Inconel® is a registered trademark of Special Metals Corporation referring to a family of austenitic nickel-based superalloys. Inconel alloys are typically used in high temperature applications.

[edit] Properties

Inconel alloys possess several properties making them well suited for service in extreme environments. Inconel is very resistant to oxidation and corrosion. When heated, inconel forms a thick, stable, passivating oxide layer, protecting it from further attack.

Inconel retains strength over a wide range of temperatures. This makes it particularly attractive in high temperature applications where aluminum and steel would "soften". Inconel's high temperature strength is attained by solid solution strengthening or precipitation strengthening (depending on the alloy). In precipitation strengthening varieties, small amounts of columbium (niobium) combine with nickel to form the intermetallic compound Ni₃Nb or gamma prime (γ'). Gamma prime forms small cubic crystals that inhibit slip and creep very efficiently at elevated temperatures.

Inconel is a difficult metal to shape using traditional techniques. It work hardens very quickly making it impossible to tap or thread with a die. External threads are machined using a lathe to "single point" the threads, or by rolling the threads using a screw machine. Holes with interal threads are made by welding or brazing threaded inserts made of stainless steel.

Welding inconel alloys may also prove difficult due to cracking and microstructural segregation of alloying elements in the heat affected zone. However, several alloys have be designed to overcome these problems.

[edit] Uses

Inconel is often encountered in extreme environments. It is common in gas turbine blades, seals, and combustors, as well as turbocharger rotors and seals, high temperature fasteners, chemical processing and pressure vessels, heat exchanger tubing, and firearm sound suppressor blast baffles. ^{[verification needed]}