An overview of the oxidation of Ni-based superalloys for turbine disc applications: surface condition, applied load and mechanical performance

In this review the role of oxidation of chromia-forming Ni-based superalloys used for rotor disc applications in gas turbines is examined. A detailed review of the oxidation performance of these alloys in air is undertaken with emphasis on oxide composition and kinetics. The actual surface condition of the component entering service is important but often overlooked during oxidation studies. The effect of shot-peening on the oxidation of Ni-based superalloys is here evaluated. The oxide growth rates and composition of these alloys was assessed with respect to their response to an applied load or stress. One area where a significant amount of research has been conducted is on the effect of oxidation on the mechanical performance, with oxidation having been shown to reduce time to crack initiation, increase fatigue crack growth rates and therefore reduce overall component fatigue life. It is argued that this enhancement in crack growth rates arises from the cracking of an oxide intrusion ahead of the crack tip, exacerbated by Stress-Aided Grain Boundary Oxidation (SAGBO).