The present study analyzes the degradation and damage processes of high-pressure rotor blades of the TV3-117 aero-engine following military training operations. Blades which had been exposed to operational conditions were extracted from the disk of second stage engine turbocompressor. The mechanical behavior of rotor blades manufactured from ZhS6K nickel-based superalloy was investigated through uniaxial fatigue testing. The results of the microstructural analyses revealed high-temperature oxidation causing degradation of the protective NiAl coating, which promotes the initiation and propagation of multiple cracks and oxide intrusions. Precipitation of Ni 3 Al in the protective coating and formation of Kirkendall porosity in the interdiffusion zone promotes crack propagation and oxide penetration. Local overheating triggered a sequence of γ/γ′ transformations, dissolution of M 23 C 6 carbides, and growth of MC carbides. Together, these changes reduce the creep resistance of ZhS6K. The observed creep cavities appear to be associated with crack formation, suggesting that creep-assisted mechanisms may contribute to fatigue crack propagation under service conditions. Fractographic analysis showed that degradation phenomena affecting the high-pressure rotor blades during operation include high-temperature corrosion and brittle fracture of the aluminide layer, combined with the propagation of multiple cracks. Regions where the NiAl coating was absent were also found to alter the geometry of the blade’s leading edge. The primary cause of premature blade failure has been attributed to the protective NiAl coating, which exhibits markedly non-homogeneous degradation across various regions of the blade’s surface.
Mára et al. (Mon,) studied this question.