Review of Progress in Quantitative Nondestructive Evaluation
This paper reports on a microstructural study of a nickel-base superalloy, Inconel 718, with a focus on quantifying precipitate density and their effects on conductivity variations. The study is motivated by eddy current (EC) characterization of residual stresses, where observed EC signals are attempted to correlate with stress profiles of shot peened superalloy surfaces. It has been observed that the correlation is less universal than anticipated, and in fact strongly influenced by the material hardness, or the aging conditions. For example, the soft sample surface exhibits significantly stronger EC signals than the fully hardened sample when both are shot peened at the same Almen intensity. Thus, the objective of the present study is to examine this complex material response against aging and shot peening treatments at the microstructure scale, by the use of techniques such as transmission electron microscopy (TEM) and scanning electron microscopy (SEM). We will describe preparations of a series of Inconel 718 samples that was aged and shot peened at various conditions, and present microstructural data obtained from SEM and TEM images such as precipitate densities, correlated with bulk properties such as the hardness and conductivity.
American Institute of Physics
Chandrasekar, Ramya; Lo, Chester C.H.; Frishman, Anatoli M.; Larson, Brian F.; and Nakagawa, Norio, "Quantification of precipitates and their effects on the response of nickel-base superalloy to shot peening" (2011). Center for Nondestructive Evaluation Conference Papers, Posters and Presentations. 41.