Microcrack Detection in Nickel-based Superalloy GH4169 Using Eddy Current-TMR Testing

Microcracks induced in superalloys under complex service conditions pose significant threats to component integrity. This paper presents an eddy current-tunneling magnetoresistance (EC-TMR) testing method for efficient and precise non-destructive evaluation of microcracks in nickel-based superalloy GH4169 (US Inconel 718) to ensure structural safety. The principle leverages highly sensitive TMR sensors to detect perturbations in eddy current-induced magnetic fields caused by microcracks. To validate the proposed method, analytical and simulation models are constructed, and experiments are conducted using the developed EC-TMR probe. The feature extraction and Fourier analysis in post-processing allow for defect quantification. Experiment results show that the proposed method can detect and quantify microcracks with minimum sizes of 0.08 mm × 0.02 mm × 0.04 mm.