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Modern jet-engine turbine blades are cast from single crystals of nickel-based superalloys because of the excellent mechanical properties that these materials exhibit at high temperatures. However, the anisotropic behavior of single crystals causes difficulties when using ultrasound to inspect these components for defects that could potentially initiate in-service. This paper describes the development of a 2D ultrasonic array system for the in situ inspection of these components. The problems associated with the inspection of anisotropic single crystal materials such as the directional dependence of the ultrasonic velocity, beam directivities in anisotropic media and the variation in the crystallographic orientation, are all addressed in this paper. In addition, constraints regarding access to the inspection location within the engine are discussed. Finally, the defect detection sensitivity and sizing capability of the developed system is evaluated. [ABSTRACT FROM AUTHOR]

The beam directivity from an ultrasonic transducer in isotropic materials is well documented. However, beam directivities in elastically anisotropic materials and their effect on ultrasonic NDE inspection has been investigated far less extensively. In this paper, analytical and numerical finite element models are developed to predict the beam directivity in a single crystal nickel-based superalloy. This material is highly anisotropic and is used widely in the gas-turbine industry. The developed models are used to investigate the effect of the crystallographic orientation on the beam directivity. In turn, the effect of beam directivity on defect detection sensitivity and characterization capability using an ultrasonic array is demonstrated. It is shown that the effect is particularly important for the accurate sizing of small defects. [ABSTRACT FROM AUTHOR]

Single crystal components are used widely in the gas-turbine industry. However, these components are elastically anisotropic which causes difficulties when performing NDE inspections with ultrasound. Recently an ultrasonic algorithm for a 2D array has been corrected to perform the reliable volumetric inspection of single crystals. For the algorithm to be implemented the crystallographic orientation of the components must be known. This paper, therefore, develops and reviews crystallographic orientation methods using 2D ultrasonic arrays. The methods under examination are based on the anisotropic propagation of surface and bulk waves and an image-based orientation method is also considered. [ABSTRACT FROM AUTHOR]