Reliable life predictions are economically vital to the Industrial Gas Turbine (IGT) Original Equipment Manufacturer (OEM). Improper understanding of component life can lead to a shortened service life interval, or in the worst case, component failure and forced outage. To understand component life, and assure safe life operation, components are qualified by demonstrating that the predicted stresses do not exceed the material capabilities. Predicted stresses are typically calculated through the Finite Element Method (FEM), while allowable material capabilities are determined using materials properties from an engineering design materials database. The materials properties in the engineering design materials database are dependent on variables such as alloy chemistry and heat treatment, which are understood and included in allowable tolerances per qualification specification limits. The current approach for materials characterization to support IGT design is primarily with separately cast slab or bar material. This standardized material testing method is intended to encompass the properties for the multitude of components cast with that material. Whilst this approach tests the compositional properties, it does not take into account the significant influence of the material property dependence on dimension/geometry and position within a component. Since the quality of the design of a component is so closely related to the materials properties, it is imperative that the materials database data accurately represent the component material. In this paper, the sources and magnitude of variability found in a cast turbine blade is investigated by testing samples machined from production cast turbine blades. These blades are cast from a polycrystalline Nickel-base superalloy commonly used for hot gas path turbine components. In order to improve design criteria, and accurately determine component life, a broader understanding of variability effects is needed. As hypothesized, the engineering design materials database properties derived from cast slab/bar material are not necessarily representative of the local properties in critical regions of the components. Additionally, variations in local properties were discovered due to location in the component, and dimensions/geometry of the specimen. The understanding gained in this investigation enables the IGT OEM to more reliably design components through a better understanding of the properties in the life limiting locations of a component. Optimizing the manufacturing processes to enhance these properties at specific locations within the component provides an additional capability to improve overall component reliability. Overall, this understanding allows for improved reliability of the IGT design life and makes use of the full potential of the chosen material for maximum economic benefit.

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