Experimental on ultrahigh frequency vibration fatigue of GH4169 nickel-based superalloy

To address the very high cycle fatigue（VHCF）issue of GH4169 nickel-based superalloy，which is widely utilized in aero-engines，a fatigue specimen subjected to 20 kHz ultrahigh frequency vibration is designed and tested utilizing a piezoelectric ultrasonic fatigue testing system. At room temperature，the P-S-N curves for VHCF of GH4169 nickel-based superalloy are obtained under various survival probabilities of 5%，50%，and 95%. The experimental findings reveal that the GH4169 material’s curve exhibits a downward trend when the fatigue life attains 107 cycles，indicating the absence of a fatigue limit and the persistence of fatigue failure. Fracture analysis results indicate that the majority of VHCF cracks initiate from the surface or subsurface of the specimen，with both single-source and multi-source cracking observed. The cracking modes encompass surface sliding cracking and non-metallic inclusion-induced sliding cracking.