Turbine Blade with Combined Structures
Original Publication Date: 2003-Dec-25
Included in the Prior Art Database: 2003-Dec-25
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The life cycle of turbine blades is limited by mechanical loading. In the airfoil of the turbine blade the creep damage and the low cycle fatigue (LCF) with dwell at high temperatures will be dominant, while in the root area the high cycle fatigue (HCF) at low temperatures can be considered as the most important problem. An excellent high temperature resistance against LCF can be achieved by using special materials like single crystal (SX) or directional solidificated (DS) blades. However, these materials usually have a bad HFC at low temperatures. An idea to improve the lifetime of a turbine vane is to combine different material structures in a single vane, e.g. a SX or DS material structure in the airfoil and a conventional cast (CC) structure in the root (Fig. 1). In this embodiment during the cast procedure the airfoil can be solidified at first by a seed crystal. When the root of the vane begins to solidify, the CC structure can be produced by varying the solidification conditions in a suitable way. The transition from the SX (or DX) to the CC zone should be in a low stress field, e.g. in the root neck. The use of superalloys with grain boundary strengthening elements can be advantageous.