The term superalloy is generally applied to those alloys that have useful levels of mechanical properties above 600-700oC, and which do not lose strength significantly when exposed to high temperatures for substantial times.
Superalloys are also required to have good "creep resistance" to limit the extent to which they will not suffer spontaneous deformation under sustained load at elevated temperature. Superalloys will usually have good oxidation resistance and respectable wear resistance at their service temperture. However they can suffer very badly form other forms of high temperature corrosion and therefore require surface engineering treatments to protect them from the operating environment.
Superalloys are fundamental to the construction of all high temperature engineering including gas turbines (aka jet engines) as well as process plants and heat treatment furnace equipment, jigs and furniture. They are therefore fundamental to our society and economy. They have been, and remain, the subject of substantial research and development activity as operating conditions become more and more demanding.
There are a number of families of superalloys, based respectively on iron, nickel or cobalt as the principal alloying element. The nickel based alloys are probably the most widely used today. Look for the names Nimonic, Inconel, Incoloy, Astroloy, Rene and Waspaloy perhaps followed by a number e.g. nimonic 90 or Inconel 718 (some times written IN718). These are the Trade Names of nickel based superalloys from different manufacturers. Some of these compositions have now been absorbed into National Standards in some countries.
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