P. B. Nagy, University of Cincinniti, Cincinnati, OH; Y. Feng, University of Cincinnati, Cincinnati, OH

Summary:

In surface-treated nickel-base superalloys the most promising NDE approach for near surface residual stress characterization is based on eddy current conductivity measurements made in the 0.1-10 MHz frequency range. This talk will focus on the main difficulties presented by electromagnetic inspection methods for residual stress profiling and assessing the level of thermo-mechanical relaxation in surface-treated nickel-base superalloy engine materials, such as IN100, IN718, and Waspaloy. The role of different material properties will be discussed in detail. In particular, the dependence of electrical conductivity and magnetic permeability on elastic and plastic deformations, i.e., residual stress and cold work, will be discussed. In addition, the adverse effect of intrinsic microstructural features in certain as-forged and precipitation hardened nickel-base superalloys, like Waspaloy and, to a lesser degree, IN718, will be also discussed.