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Contribution of High Mechanical Fatigue to Gas Turbine Blade Lifetime during Steady-State Operation

1
Power Generation Laboratory, Korea Electric Power Corporation Research Institute, Munjiro 105, Yuseong-gu, Daejeon 34056, Korea
2
School of Advanced Materials Engineering, Chung-Nam National University, 99 DaeHak-ro, Yuseong-gu, Daejun 34134, Korea
3
School of Energy System Engineering, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 06974, Korea
*
Author to whom correspondence should be addressed.
Coatings 2019, 9(4), 229; https://doi.org/10.3390/coatings9040229
Received: 12 February 2019 / Revised: 19 March 2019 / Accepted: 22 March 2019 / Published: 31 March 2019
(This article belongs to the Special Issue Science and Technology of Thermal Barrier Coatings)
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Abstract

In this study, the contribution of high thermomechanical fatigue to the gas turbine lifetime during a steady-state operation is evaluated for the first time. An evolution of the roughness on the surface between the thermal barrier coating and bond coating is addressed to elucidate the correlation between operating conditions and the degradation of a gas turbine. Specifically, three factors affecting coating failure are characterized, namely isothermal operation, low-cycle fatigue, and high thermomechanical fatigue, using laboratory experiments and actual service-exposed blades in a power plant. The results indicate that, although isothermal heat exposure during a steady-state operation contributes to creep, it does not contribute to failure caused by coating fatigue. Low-cycle fatigue during a transient operation cannot fully describe the evolution of the roughness between the thermal barrier coating and the bond coating of the gas turbine. High thermomechanical fatigue during a steady-state operation plays a critical role in coating failure because the temperature of hot gas pass components fluctuates up to 140 °C at high operating temperatures. Hence, high thermomechanical fatigue must be accounted for to accurately predict the remaining useful lifetime of a gas turbine because the current method of predicting the remaining useful lifetime only accounts for creep during a steady-state operation and for low-cycle fatigue during a transient operation. View Full-Text
Keywords: degradation; high mechanical fatigue; hot gas path components; gas turbine lifetime; gas turbine blade degradation; high mechanical fatigue; hot gas path components; gas turbine lifetime; gas turbine blade
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Chang, S.Y.; Oh, K.-Y. Contribution of High Mechanical Fatigue to Gas Turbine Blade Lifetime during Steady-State Operation. Coatings 2019, 9, 229.

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