Shear-mode Fatigue Strength of Ni-based Superalloy Alloy718

Abstract

In order to establish a comprehensive understanding of the fatigue strength of precipitation-strengthened materials, fatigue tests were carried out under pure axial and torsional cyclic loading conditions respectively. The materials investigated were two types of Alloy718; one was solution-treated and another was precipitation-strengthened. The shear-mode fatigue propagation in the principal shear stress direction was observed despite loading conditions. The threshold stress intensity factor ranges for shear-mode crack, ΔK_τth, were investigated for each testing condition. Based on the results, the effect of the normal stress on the critical plane to the value of ΔK_τth was discussed.