Cyclic dwell fatigue behaviour of single crystal Ni-base superalloys with/without rhenium

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Proceedings titleProceedings of the International Symposium on Superalloys
Conference12th International Symposium on Superalloys, Superalloys 2012, 9 September 2012 through 13 September 2012, Seven Springs, PA
Pages501508; # of pages: 8
SubjectCreep-fatigue; Cyclic stress-strain behavior; Fatigue experiments; Isotropic coarsening; Low cycle fatigues; Microstructural analysis; Ni-base superalloys; Second generation; Fatigue of materials; Nickel; Single crystals; Superalloys
AbstractIn this study, compressive dwell (C-D) and no-dwell (N-D) low-cycle fatigue (LCF) behaviours of several single crystal Ni-base superalloys, including CMSX-4, LSC-11 and LSC-15, were studied under strain-controlled zero-compression (RE = -co) loading at 1100°C. LSC-11 and LSC-15 are new alloys developed by 1H1 Corporation, Japan with 0.8 wt% Re and without Re addition, respectively, as reduced-cost alternatives to the second generation single crystal Ni-base superalloys. The fatigue experiments were conducted with or without a two-minute dwell (hold) in compression and total strain ranges of 0.7%, 0.6% and 0.5% on uncoated specimens in the [001] orientation. Examination of the cyclic stress-strain behavior revealed that the initially compressive mean stress relaxed to approximately zero stress in N-D tests, while compressive hold resulted in the development of a tensile mean stress during C-D fatigue. Cyclic stress softening was observed under all test conditions. Microstructural analysis of tested specimens showed that N-D fatigue promoted isotropic coarsening of the γ′ precipitates, while C-D loading resulted in the formation of discontinuous γ′ rafting parallel to the loading direction. Fatigue cracks initiated from the specimen surface from regions of localized oxide attack. All alloys were compressive dwell sensitive. C-D fatigue lives were 4-15× shorter than N-D when the same alloys were considered. CMSX-4 exhibited 1.5-3× N-D fatigue life advantage over alloys LSC-11 and LSC-15. Under C-D fatigue the life advantage of CMSX-4 was 20-50% greater than alloys LSC-11 and LSC-15. The differences in these behaviours could be attributed to Re content and oxidation.
Publication date
AffiliationNational Research Council Canada (NRC-CNRC); Aerospace (AERO-AERO)
Peer reviewedYes
NPARC number21269161
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Record identifier0a71b1a9-c409-440a-8204-04a94a644319
Record created2013-12-12
Record modified2016-05-09
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