Recent developments in nickel-based superalloys for gas turbine applications: Review

Nickel-based superalloys are used in gas turbines due to their mechanical properties at high temperatures. Increasing demand for higher efficient engines has led to the development of single-crystal superalloys that avoid detrimental grain boundary effects that weaken material at high temperatures. However, features like dynamic recrystallization and stress corrosion cracking are typical for polycrystalline and single-crystal materials. The single crystal alloys are used explicitly in aerospace applications as gas turbine blades, while the wrought alloys are confined to turbine disks and auxiliary applications. In this review, a lateral approach is discussed on the detrimental effects of non-cubic precipitates and the effects of partial pressure of oxygen in the working fluid on the oxidation of alloys. The effects of adding rare earth elements on the alloys' solidification properties, strength, micromechanics, etc., have almost become an intrinsic part of studying superalloys. The phenomenon of strengthening and microstructural features are sensitive to temperature and applied loads, yet the routes of their mechanisms are not entirely explored. It is observed that decades of alloy development have significantly impacted the rate of response of slip systems to the working environment. Still, the native slip system < 110 > {111} remains unchanged, and the temperature of anomalous yielding, where an inflection in the material's yield behaviour is observed, is not significantly affected by composition. However, the increasing demand for fuel efficiency in the aviation industry attracts researchers to develop highly efficient superalloys with higher refractoriness.