The Influence of Orientation on the Fatigue of Directionally Solidified Superalloys

Abstract

Directionally solidified (DS) nickel base superalloys were introduced to improve performance of jet engine turbine airfoils. The DS process imparts improved creep-rupture (1) and thermal fatigue (2) resistance in the solidification direction due to preferred crystallographic texture and grain boundary orientation, Figure 1. Although the solidification direction is the prime load bearing direction in turbine airfoils, the actual stress states are in general quite complex as a result of thermal stresses and geometric constraints. This complexity inevitably leads to the generation of stress in directions other than the solidification direction. For satisfactory airfoil performance, the