Parameters Controlling the Thermal Fatigue Properties of Conventially-Cast and Directionally-Solidified Turbine Alloys

Leverant, G. R.; Strangman, T. E.; Langer, B.S.

doi:10.7449/1976/superalloys_1976_285_295

Cited by 14 publications

(9 citation statements)

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“…In phase (IP) thermo-mechanical fatigue cycling were conducted under mechanical strain control in the 50-550C temperature range using a MTS 810 servo-hydraulic thermo-mechanical fatigue machine. An extensometer with a 12-mm gauge length was symmetrically attached to the specimen over the notch as seen in the experimental setup in Figure [2]. All tests were conducted in displacement control by prescribing the displacement of the extensometer gauge length.…”

Section: Methodsmentioning

confidence: 99%

“…Furthermore all tests were performed with a nominal mechanical strain ratio of . To enable thermal cycling, induction heating has been used in combination with convection cooling from compressed air distributed onto the specimen by two cooling nozzles as seen in Figure [2]. The induction coil was designed in such a way that during heating, the main part of the heat input occurs at the shoulders of the specimen outside the gauge section of the specimen.…”

Section: Methodsmentioning

confidence: 99%

“…The pioneering work in this field where conducted by Leverant and co-workers at Pratt & Whitney Aircraft in the 70'ies [1][2][3] when the influence of oxidation-resistant protective coatings on fatigue crack initiation as well as on propagation of coating-initiated cracks into the superalloy substrate were studied. The approach was based on the combination of a specimen design and testing method that could simulate the various straintemperature phase relationships experienced in turbine airfoils, including measurement of thermo mechanical fatigue crack growth.…”

Section: Introductionmentioning

confidence: 99%

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Hold-time effect on the thermo-mechanical fatigue crack growth behaviour of Inconel 718

Moverare

Gustafsson

2011

Materials Science and Engineering: A

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In-phase TMF crack growth testing with different lengths of the hold time at the maximum temperature of 550C has been conducted on Inconel 718 specimens. Focus has been on establishing a method for TMF crack growth testing and investigating the effect of high temperature hold times on the TMF crack growth of the material. The tests are compared to isothermal crack propagation tests and show good correlation. It is concluded that the controlling effect of the crack growth is an embrittlement of the material. This embrittlement is related to the concept of a damaged zone active in front of the crack tip. The size of this damaged zone will control the crack propagation rate and therefore it does not matter if the load is cycled under isothermal or TMF conditions.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hold-time effect on the thermo-mechanical fatigue crack growth behaviour of Inconel 718

Moverare

Gustafsson

2011

Materials Science and Engineering: A

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“…This study presents a detailed analysis of all the elements which had an influence on a 37.5 MW gas turbine third stage bucket failure. The initiation of the crack/fracture in the bucket tip shroud took the transgranular form, which is typically related to excessive stress owing to a fatigue mechanism 11 . The commensurate loss of a load bearing cross‐sectional area of the bucket tip shroud by the conversion of metal to the corrosion product (scale) had significantly increased the tip shroud stresses and abruptly reduced its life.…”

Section: Discussionmentioning

confidence: 99%

Failure analysis of gas turbine last stage bucket made of Udimet 500 superalloy

Mazur

Kubiak

Mariño-Lopez

2002

Fatigue Fract Eng Mat Struct

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This study presents the failure analysis of the 37.5 MW gas turbine third stage buckets made of Udimet 500 (U‐500) superalloy. The buckets experienced repetitive integral tip shroud fractures assisted by a low temperature (type II) hot corrosion. A detailed analysis of all elements which had an influence on the failure initiation was carried out, namely: the commensurate loss of a load bearing cross‐sectional area of the bucket tip shroud by the conversion of metal to the corrosion product (scale) and related increase in stress; the influence of the tip shroud microstructure, e.g. a presence of equiaxed and columnar grains, their distribution and orientation; evidence of the transgranular fracture initiation and intergranular creep mechanism fracture propagation. Finally, the most probable mechanism for bucket damage, conclusions and recommendations to prevent failures of the buckets are presented.

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“…In fact, the study of fatigue has generally bypassed real thermal fatigue loading partly because isothermal tests are relatively simple to perform, but also because it has often been felt that such tests carried out at the maximum service temperature would give worst case results. However, several studies which have compared fatigue resistance under thermal cycling conditions with that in isothermal tests have shown that in many cases, the latter, rather than giving a worst case situation, can seriously overestimate the real fatigue life [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%