Structure and properties of gas turbine blade metal after long-term operation
DOI:
https://doi.org/10.15407/mom2026.01.003Keywords:
heat-resistant nickel-based alloy, turbine blades, high-pressure turbine, microstructure, mechanical properties, long-term serviceAbstract
The paper presents the results of a comprehensive investigation of the microstructural state and mechanical properties of high-pressure turbine blades of the GTC-10I gas turbine unit manufactured from the heat-resistant nickel-based alloy ChS70-VI after long-term industrial service. The study was carried out on blades with operating times of 20,000, 30,000, and 50,000 hours, which made it possible to analyze the evolution of the material structure at different stages of service life.
Metallographic examination revealed characteristic features of microstructural degradation in the blade airfoil material as a function of service duration and operating temperature. It was shown that prolonged exposure leads to progressive coarsening and coagulation of the strengthening γ′ phase, accompanied by a decrease in its dispersion and redistribution of phase constituents. The most pronounced structural changes were observed in the high-temperature regions of the airfoil, whereas the blade root section, operating under lower temperature conditions, retained a relatively stable microstructural state throughout the investigated service period.
Mechanical testing demonstrated a gradual reduction in both strength and ductility with increasing service time, which correlates well with the observed microstructural transformations. After 50,000 hours of operation, the structural changes become largely irreversible and are accompanied by a sharp deterioration of mechanical properties, indicating a limiting condition for further safe operation of the blades without refurbishment or recovery procedures.
The obtained results can be applied to residual life assessment of GTC-10I high-pressure turbine blades made of the ChS70-VI alloy and to substantiation of allowable service limits for industrial gas turbine units operating under long-term thermal loading.
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Copyright (c) 2026 S. B. Belikov, O. S. Mykhaylov
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