Iron-nickel-based superalloys, high-temperature

Nickel based superalloys are one of three groups of materials used for demanding, high-temperature applications such as jet engines and gas turbines (e.g., Inconel X-750). The other two groups are iron-based and cobalt-based superalloys. 

Hastelloy X (HastX) is a nickel-based superalloy used in a variety of applications [Brown, 1992]. Its composition is 49% nickel, 22% chromium, 18% iron, 9% molybdenum, 1.5% cobalt and 0.5% tungsten. The melting point of HastX is about 1530 K, and it has a density of 8.22 g/cc. This material has been suggested as a possible reactor material for a variety of reasons. HastX is a material with decent high temperature characteristics. Hastelloy is also noted for excellent corrosion, oxidation and carburization resistance at the desired temperatures. Finally, Hastelloy-X is a commonly used metal whose properties are well understood. The expected peak temperature of Hastelloy-X is roughly 875 K when used for the pressure vessel of the reactor. 

The term superalloy is used for a group of nickel-, iron-nickel-, and cobalt-based high-temperature materials for applications at temperatures > 540 °C. It is useful to compare the main subgroups in terms of the strengthening mechanisms applied and stress-rupture characteristics achieved, as shown in Fig. 3.1-127. In this section iron-nickel- and nickel-based superalloys are covered whereas cobalt-based superalloys are dealt with in Sect. 3.1.6.3. Nickel-based superalloys are among the most complex metallic materials with numerous alloying elements serving particular functions, as briefly outlined here. 

Superalloys are alloys that display a particularly excellent ability to resist deformation under stress at high temperatures along with good resistance to corrosion and great surface stability. Most often, a superalloy involves nickel, cobalt, or nickel-iron as the base alloying element. Superalloys have been used primarily in turbines and in the aerospace industry. 

Iron-, nickel-, and cobalt-based alloys used primarily for high-temperature applications are known as superalloys. The iron-based grades, which are less expensive than cobalt- or nickel-based grades, are of three types ... 

The nickel-based alloys are sometimes referred as superalloys. They have been defined as those possessing good high-temperature strength and oxidation resistance and are alloys of nickel, cobalt, and iron that contain... 

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