Two industrial gas turbine blades made from a conventionally cast Ni-base superalloy GTD-111, one new and the other rejuvenated, were removed from the same machine after a particular operational cycle for an examination in order to determine the effect of rejuvenation on the material’s behavior during service. It was found that service-induced changes in the microstructure, such as γ′-phase coarsening and coalescence, excessive grain-boundary secondary M23C6 carbides formation, and primary MC carbides decomposition, were noticeably more advanced in the rejuvenated blade. The stress-rupture life of the rejuvenated blade decreased significantly compared to that of the new blade after the same number of hours in service. The cause of this decrease appears to be related to a release of additional amounts of carbon and carbide-forming elements into the matrix during rejuvenating heat treatment as a result of the primary MC carbide decomposition.
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Acknowledgments
The author would like to thank Dr. Vladi Levit, senior research scientist, the Department of Material Science and Engineering, The Ohio State University, and Dr. Michael J. Kaufman, professor and chair of the Department of Material Science and Engineering, University of North Texas, for a valuable discussion. The author also acknowledges the use of the analytical facilities in the Major Analytical Instrumentation Center of University of Florida during the course of this work.
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Lvova, E. A Comparison of Aging Kinetics of New and Rejuvenated Conventionally Cast GTD-111 Gas Turbine Blades. J. of Materi Eng and Perform 16, 254–264 (2007). https://doi.org/10.1007/s11665-007-9046-y
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DOI: https://doi.org/10.1007/s11665-007-9046-y