Foreign object damage (FOD) is a common issue during aero-engine operation process, which can usually lead to high-cycle fatigue (HCF) fracture failure of fan and compressor blades. To investigate the effect of post-impact heat treatment on the HCF performance of compressor blade alloy GH4169 with FOD, this study uses an FOD simulation device to conduct impact tests on specimens. The impacted specimens are subjected to heat treatment of varying duration, followed by HCF testing. The results show the presence of adiabatic shear bands (ASB) on the exit side of the impact crater, with lengths mostly in the range of 100-250 μm. HCF tests reveal that the microscopic defects generate by FOD significantly reduce the fatigue strength of GH4169 alloy. But its mechanical properties and fatigue resistance are enhanced to some extent by certain post-impact heat treatment process, and the beneficial influence on the HCF strength is most evident at the stress ratio of -1 condition associated with the fatigue crack initiation mode transition from ASB cracking to slip band cracking. These findings show that post-impact heat treatment can somewhat restore the fatigue performance of GH4169 alloy after FOD, contributing to improved service life and reliability of aero-engine compressor blades.

In this study, high-speed ballistic impact tests were conducted on GH4169 alloy samples with the aeroengine compressor blade leading edge feature to simulate the notch-type foreign object damages (FOD). Macroscopic and microscopic characterization of FOD and high cycle fatigue tests were performed to investigate the effect of FOD depth on GH4169 alloy fatigue strength along with numerical analysis using Kitagawa-Takahashi diagram. Results show the incident side of notch-type FOD is relatively smooth, whereas the exit side is rugged. The FOD depth ranges from 0.18mm to 1.33mm, and the fatigue strength of damaged samples is 37.93%~97.04% of the undamaged samples. As FOD depth increases, damage length, material losses and stress concentration coefficient of the FOD increase significantly along with the increasing adiabatic shear bands, micro voids and cracks, resulting in fatigue strength reduction. Numerical analysis indicates that the Kitagawa-Takahashi diagram can provide a basic model for the design of FOD tolerance.