Research on High-Temperature Eddy Current Testing Method for Tail Nozzle of Aviation Engine

The tail nozzle of an aero-engine, made of nickel-based superalloy, is a critical component in the hot section and is prone to thermal fatigue cracks due to high temperature and high pressure. Traditional non-destructive testing (NDT) methods have limitations in high-temperature environments. This paper addresses the temperature drift issue of conventional eddy current sensors by proposing a single-excitation dual-detection symmetric U-shaped differential probe. This design suppresses temperature drift through magnetic field balancing and differential signal processing. Based on multi-physics coupling theory, a simulation model is developed to reveal the nonlinear attenuation behavior of electrical conductivity of the relevant materials in the temperature range of 20~200°C, and the correlation between defect depth and signal temperature drift. The environmental adaptability of the differential probe is confirmed to be superior. A high-temperature eddy current detection system is developed, and a platform is built for testing. Defect detection in the range of 0.3 to 1.2 mm at 20~200 °C shows that both the real and imaginary parts of the defect signal exhibit nonlinear attenuation, with deeper defects being more sensitive to temperature changes. High-temperature tests confirm that the newly developed probe effectively suppresses temperature drift in the range of 20~200 °C and performs better than traditional probes.