Abstract
This article presents a failure analysis of 37.5 mW gas turbine third stage buckets made of Udimet 500 superalloy. The buckets experienced repetitive integral tip shroud fractures assisted by a low temperature (type II) hot corrosion. A detailed analysis was carried out on elements thought to have influenced the failure process:
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a)
the stress increase from the loss of a load bearing cross-sectional area of the bucket tip shroud by the conversion of metal to the corrosion product (scale),
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b)
influence of the tip shroud microstructure (e.g., a presence of equiaxed and columnar grains, their distribution and orientation),
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c)
evidence of the transgranular initiation, and
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d)
intergranular creep mechanism propagation.
The most probable cause of the bucket damage was the combination of increased stresses due to corrosion-induced thinning of the tip shroud and unfavorable microstructures in the tip shroud region.
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Mazur, Z., Kubiak, J. & Mariño-Lopez, C. Failure analysis of gas turbine last stage bucket made of udimet 500 superalloy. Practical Failure Analysis 2, 51–57 (2002). https://doi.org/10.1007/BF02715419
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DOI: https://doi.org/10.1007/BF02715419