Abstract
In this study, biaxial thermo-mechanical fatigue (TMF) tests simulating actual blade loading condition have been carried out using a directionally solidified super alloy which is typically used in 1300C class gas turbine blades. Fatigue lives under biaxial TMF life could not be correlated with Mises equivalent strain range. An equivalent shear strain range for the Ni based DS superalloy was derived based on Γ-plane theory, and the biaxial TMF life was well correlated with the equivalent shear strain range. It was found that fatigue life was reduced to 1/5 by introducing 6 minutes strain hold time at the maximum temperature. This life reduction may be occurred due to increasing of tensile stress during strain hold period.
