Nickel-Based Superalloys

Nickel-based superalloys are an exceptional class of structural materials for high temperature applications, particularly in the challenging environment of the turbine sections of aircraft engines. Continued improvements in the properties of these materials have been possible through close control of chemistry and microstructure as well as the introduction of advanced processing technologies. Surface modification by application of coating technology concurrent with the introduction of directional structures and then single crystals, has extended the useful temperature range of superalloys. Further improvements are likely with the development and implementation of tools for alloy design, microstructure-process evolution, and mechanical-property modelling. To date, six generations of single crystal (SC) nickel-based superalloys have been developed with improved creep properties and phase stability. Therefore it appears that the evolution of advanced nickel-based superalloys is a never ending process, and their replacement in turbine engine applications seems to be impossible at least for a few more decades. The present chapter is a brief review of various aspects pertaining to chemical composition, heat treatment, microstructure, properties and applications of both cast, and wrought alloys as well as the evolution of advanced cast nickel-based superalloys.