Conventional turbine blades for turbomachinery apparatus usually are of a single alloy configuration, generally cast, with the alloy selected to meet certain high temperature strength and environmental requirements. Strength in the dovetail region of such a fluid directing element is dictated by the low temperature strength of the alloy. In high tip speed turbomachinery, very high centrifugal loads must be transferred from the blade dovetail to the wheel dovetail in which it is mounted at the interface between the two. Thus, the life of the blade dovetail is limited by low cycle fatigue whereas the mating wheel dovetail, which can be a lower temperature material, generally possesses extremely high cyclic capability.
As the turbine temperatures and speeds are increased in advanced gas turbines to improve efficiency, it has become increasingly more difficult to satisfy all of the requirements of such components involved.