Over the last decade there has been a focused effort in the aerospace industry to improve the inspection sensitivity for jet engine rotating hardware. Today, inspection sensitivity is measured with calibration targets where known diameter holes are drilled into metal blocks at various depths, angles, or geometries to simulate material defects (e.g., #1 FBH). Real-world production defects would be significantly more effective to develop and validate the capability of different inspection methods. However, when such defects are found in production hardware, they are necessarily destructively analyzed to drive critical root cause analyses to ensure fleet safety and are no longer available for nondestructive (NDE) technique development.
This work describes the progression of creating more realistic synthetic defect targets in a nickel-based superalloy to bridge the gap between today’s FBH standards and natural defects for NDE technique development. A powder metallurgy (PM) manufacturing method is utilized where the grain size can be controlled to simulate the representative grain-produced noise found in either PM or cast and wrought (C&W) hardware. Using this approach, defects found in both PM hardware, such as oxide strings or clusters, and in C&W hardware, such as oxy-carbo-nitride clusters (OCNCs) or dirty white spots (DWS) are developed. Additionally, a method to create fine, in-situ cracks in known, subsurface locations is discussed. The overall methods of manufacture will be described and detailed micrographs and preliminary ultrasonic NDE scan results will establish the link between synthetic seed and inspection sensitivity.