SUPER ALLOY

Jet engine parts, turbo-superchargers, extreme high-temperature applications.

An iron-base, cobalt-base, or nickelbase alloy that combines high-temperature mechanical properties, oxidation resistance and creep resistance to an unusual degree. Constitutions of these alloys are as follows. Iron-base: 10–45% nickel, 13–19% chromium, 1.3–6% molybdenum, balance iron. Cobalt-base: 0–26% nickel, 0–26% chromium, 0–15% tungsten, balance cobalt. Nickelbase: 55–75% nickel, 10–20% chromium, 0–6% aluminum, 0–5% titanium. All contain less than 0.5% carbon, plus other special ingredients. Superalloys can be used up to 2500F.

Superalloys are nickel, Fe–Ni, and cobalt-basealloys generally used at temperatures aboveabout 538°C. The Fe–Ni-base superalloys arean extension of stainless steel technology andgenerally are wrought, whereas cobalt-base andnickel-base superalloys can be wrought or cast.The more highly alloyed compositions normallyare processed as castings. Fabricated caststructures can be built up by welding or brazing,but many highly alloyed compositions containinga high amount of hardening phase are difficultto weld. Properties can be controlled byadjustments in composition and by processingincluding heat treatment.