NDT methods for revealing anomalies and defects in gas turbine blades

The amount of energy produced by gas turbines is increasing all over the world. One important part in these gas turbines is the turbine blading. Improved blades and vanes are being introduced while the industry also uses the old generation of blade types. Applicable NDT methods are needed for all blade types. Many NDT-methods can be applied in laboratory environment. This overview describes a variety of methods for blade inspection such as dye penetrant, eddy current, radiography and ultrasonic methods. Some of these methods are considered on the basis of the experience gained in measurements. One new UT-method is described, easily transferable for practical inspections on site. A wide aperture VTT probe has been developed for the purpose. With this special probe different blade properties can be measured, such as coating thickness, detection and size of cracks, delaminations as well as mechanical properties.