The influence of crystal orientations on fatigue life of single crystal cooled turbine blade

A method based on the orthotropic elastic finite element analysis (FEA) has been presented to analyze the fatigue life of cooled turbine blades made of nickel-based single crystal superalloy (SC). Special attention was put on the influence of the crystallographic orientations on the strength and fatigue life of SC cooled turbine blades. It is shown that, due to the influence of the temperature distribution and complexity of cooling tunnel, the place of the maximum resolved shear stress in the blade is not corresponding to the most dangerous place, where results in the minimum fatigue life. For the SC cooled turbine blades studied in the paper, as the same of the most commercial SC blades in the world market, the axial direction is cast to [0 0 1] crystallographic orientation within 15° deviation, and the other two directions are in random. It is found that the randomness of the two directions has only limited influence on the distributions of Mises stress and the maximum resolved shear stress in the blade. But the deviation of the axial direction of the blade has obvious influence on the stress distribution, and the influence of the deviation and randomness orientations on the fatigue life is also obvious. Finally, the benefit of the optimization of the crystallographic orientations of SC cooled turbine blades on the fatigue life is highlighted.