Superalloys are designed to be used at temperatures of 540oC and higher , typically up to 0.7 x their absolute melting temperature, which may be up to around 1000oC. At 760oC most superalloys have a yield strength in excess of 500MPa.
They are also corrosion resistant. About three quarters of superalloys are used in aerospace, typically about one half of the weight of a modern jet engine is made up of superalloys.
There are 3 types:
Nickel based - may be wrought or cast. Typically more than 40% Ni, 10-20% Cr, up to 10% Al and Ti, 5-10% Co and small amounts of B, Zr and C. Mo, W and Nb are also commonly added.
Cobalt based - may be wrought or cast. Typically contain 35-60% Co, 20-30% Cr, up to 35% Ni with some W and Mo.
As well as jet engines, these alloys are also used for fixtures and jigs to be used in furnaces.
Most superalloys are propriertary, the following shows the main types and trade names:
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David J Grieve, 23rd May 2005.