Ultrasonic characterization for directional coarsening in a nickel-based superalloy during creep exposure

Abstract

The effects of directional coarsening of gamma' precipitates in nickel-based superalloy on ultrasonic attenuation coefficient and nonlinearity during creep exposure were investigated in this study. The cuboidal gamma' precipitates coarsened preferentially in the direction perpendicular to the applied stress axis during the creep deformation. The length (a) of the gamma' precipitates increased with creep time, while the width (b) increased slightly. Here, the increase in ultrasonic attenuation coefficient and nonlinearity with increasing creep time is discussed in relation to the directional coarsening of gamma' precipitates, which was closely related to the scattering and distortion of the ultrasonic waves. We suggest that ultrasonic attenuation coefficient and nonlinearity can potentially be used for characterization of creep damage in nickel-based superalloys.