A review on atom probe and correlative microscopy studies of corrosion in nickel-based superalloys

Abstract

This article discusses challenges faced in the development of new Ni-based superalloys for applications in the hottest sections of turbine engines and the use of atom probe tomography and correlative microscopy for characterization of these complex alloys with regards to microstructural and compositional design. The two strengthening phases γ and γ′ are introduced and the precipitation of topologically close-packed phases and their potential detrimental effects on superalloy properties are reviewed. Mechanisms of environmental degradation, namely oxidation and hot corrosion, are elucidated and recent research studies on a new phenomenon of hot corrosion at relatively low temperatures below 600°C are discussed. The effect of individual alloying elements on superalloy properties is reviewed, with a focus on Mo and W. The use of atom probe in correlation with state-of-the-art microscopy, spectroscopy and diffraction techniques to study and understand oxidation and corrosion of Ni-based superalloys, including crack tip investigations, is presented.