Kinetics of γ’ precipitation and its influence on fatigue crack growth behavior of a new single-crystal nickel- based superalloy (cmsx-4g) at room temperature |
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Authors: | A Sengupta S K Putatunda |
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Affiliation: | (1) Department of Chemical and Materials Science and Engineering, Wayne State University, Detroit, Michigan;(2) Department of Chemical and Materials Science and Engineering, Wayne State University, Detroit, Michigan |
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Abstract: | An investigation was carried out to determine the growth kinetics of γ precipitates in a newly developed single-crystal nickel-base
superalloy containing rhenium (CMSX- 4G). The investigation also examined the influence of γ’ precipitates (size and distribution)
on fatigue crack growth behavior of the material in a room-temperature ambient atmosphere. The influence of load ratio on
fatigue threshold of the material and crack growth mechanisms in fatigue was also studied. Compact tension specimens were
prepared from a single-crystal nickel-base superalloy, CMSX-4G, with the (001) crystallographic direction. These specimens
were given two different heat treatments to produce two different γ’ size precipitates. Fatigue crack growth behavior of these
materials was studied at three different load ratios (R = 0.10, 0.50, and 0.90) in room-temperature ambient atmosphere. The results of the present investigation demonstrate that
rhenium additions in CMSX-4G substantially lowers the γ coarsening kinetics of this alloy. The smaller γ’ precipitate size
was found to be beneficial for fatigue resistance and has resulted in a higher fatigue threshold and lower fatigue crack growth
rate in the threshold region. The fatigue threshold was found to decrease with an increase in load ratio. The crack growth
mechanism in the threshold region was found to occur by a combination of microvoid coalescence and striations. |
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Keywords: | crack growth fatigue kinetics nickel alloys performance test: fatigue precipitation superalloys |
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