Evaluation of Fatigue-Creep Interaction Life Using Total Strain Energy Criterion for Directionally Solidified Superalloy René 80H

Abstract

This paper examines the strain controlled fatigue-creep interaction (FCI) life of directionally solidified (DS) superalloy René 80H.
The author previously proposed a frequency-modified total strain energy parameter, obtained from the total tensile strain energy and tensile loading time, for use in evaluating the failure life of equiaxial Ni and Co based superalloys under FCI conditions. The present paper examines the applicability of this parameter for predicting the FCI life of DS René 80H.
The FCI life prediction by the total strain range was first evaluated. It was found that the FCI life of the specimens cut in parallel to the DS direction of a directionally solidified plate was longer than that of the specimens cut in transverse to the DS direction. In addition, the specimen life under tensile hold time conditions was longer than under compressive hold time conditions.
The FCI life prediction by the frequency-modified total strain energy parameter was evaluated next. For the specimens in both directions, there is a linear correlation between this parameter and the cycles to failure. Therefore, it is concluded that the FCI life prediction for DS René 80H can be made by using this parameter.