Abstract
The effect of brittle coating precracking on the fatigue behavior of a high-activity aluminide-coated single-crystal nickel-base superalloy has been studied using hollow cylindrical specimens at test temperatures of 600 °, 800 °, and 1000 °. Three types of precrack were studied: narrow precracks formed at room temperature, wide precracks formed at room temperature, and narrow precracks formed at elevated temperature. The effect of precracking on fatigue life at 600 ° was found to depend strongly on the type of precrack. No failure was observed for specimens with narrow room-temperature precracks because of crack arrestvia an oxidation-induced crack closure mechanism, while the behavior of wide precracks and precracks formed at elevated temperature mirrored the non-precracked behavior. Crack retardation also occurred for narrow room-temperature precracks tested at 800 °—in this case, fatigue cracks leading to failure initiated in a layer of recrystallized grains on the inside surface of the specimen. A significant reduction in fatigue life at 800 ° relative to non-precracked specimens was observed for wide precracks and elevated temperature precracks. The presence of precracks bypassed the initiation and growth of coating fatigue cracks necessary for failure in non-precracked material. No effect of precracking was observed at 1000 °.
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Formerly Research Student, Department of Materials Science and Metallurgy, University of Cambridge.
Formerly Lecturer, Department of Materials Science and Metallurgy, University of Cambridge CB2 3QZ, United Kingdom.
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Totemeier, T.C., Gale, W.F. & King, J.E. Isothermal fatigue of an aluminide-coated single-crystal superalloy: Part II. effects of brittle precracking. Metall Mater Trans A 27, 363–369 (1996). https://doi.org/10.1007/BF02648413
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DOI: https://doi.org/10.1007/BF02648413
Keywords
- Fatigue
- Material Transaction
- Fatigue Crack
- Fatigue Life
- Strain Range