DEVELOPMENT OF ULTRASONIC INSPECTION FOR A BONDED SUPERALLOY BLADE

摘要

Ultrasonic testing and imaging has proven effective in detecting defects in TLPB bondlines of specimens simulating the geometry of a turbine blade. A flat bottom hole with a diameter of 1/32" was found to be detectable with a 20 MHz 0.25" diameter contact probe. The same flat bottom hole could be imaged in a C-scan using a 15 MHz, focused probe. In both immersion and contact testing the amplitude of the signal reflected from a defect showed good correlation with the size of the defect. An unbonded region in a production turbine blade measuring approximately 10 mm was detected. As with the I-beam specimen, the results obtained with immersion and contact testing showed good correlation. Based on this study conducted on a turbine blade and on a bonded blade, ultrasonic measurements can be used for flaw detection and quality assessment of bonded single crystal turbine blades. In principle, the entire ultrasonic inspection process of a single crystal part can be modeled, based on the complete geometry and crystalline orientation of the part.