Microstructural Conditions Contributing to Fatigue Variability in P/M Nickel-Base Superalloys

Porter, Iii.; Li, K.; Caton, M. J.; Jha, S. K.; Bartha, Bence B.; Larsen, J. M.

doi:10.7449/2008/superalloys_2008_541_548

Cited by 8 publications

(7 citation statements)

References 9 publications

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“…2. This separation in fatigue lifetimes, known as bimodal or competing-modes fatigue, has been observed in a wide range of alloys, including the superalloys: Rene'95 [21,22], Rene'88DT [23], IN100 [8,[24][25][26][27][28][29], Waspaloy [30], the single crystal alloy PWA 1484 [31], the titanium alloys Ti-10-2-3 [23,[32][33][34], Ti-6Al-2Sn-4Zr-6Mo [35][36][37][38][39][40][41][42], Ti-6Al-4V [43][44][45][46][47], gamma titanium aluminides [48,49], the aluminum alloy 7075-T651 [50], and others. Although such a separation of fatigue response has been known for some time [51], the significance of this behavior has not yet been generally captured in the strategies for fatigue design of turbine engine materials.…”

Section: Life Limits and Competing-mode Of Fatiguementioning

confidence: 99%

Reducing uncertainty in fatigue life limits of turbine engine alloys

Larsen

Jha

Szczepanski

et al. 2013

International Journal of Fatigue

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a b s t r a c tIn probabilistic design of materials for fracture-critical components in modern military turbine engines, a typical maximum design target risk (DTR) is 5 Â 10 À8 component failures/engine flight hour. This metric underscores the essential role of safety in a design process that simultaneously strives to achieve performance, efficiency, reliability, and affordability throughout the life cycle of the engine. Traditionally, the design and life management approaches for engine materials have typically relied on extensive testing programs to produce large databases of fatigue data, from which statistically based life limits are derived by extrapolation from the mean fatigue behavior. However, we have found that the statistical behavior of fatigue lifetimes under a given test condition often exhibits a bimodal form, and that the trends in mean vs. minimum fatigue lifetime typically respond differently to loading or to microstructural variables. Under such circumstances, the underlying life-limiting mechanisms appear to exhibit a probabilistic microstructural hierarchy in fatigue resistance that is controlled by susceptibility of local microstructural neighborhoods to early damage and the growth of small cracks. These findings suggest that significant opportunities may exist for reductions in uncertainty in materials life-cycle prediction and management, if such hierarchies can be understood and controlled. This paper explores the potential implications of these findings, and a number of possible approaches are suggested for incorporating the insights of life-limiting fatigue into methods of integrated computational materials engineering (ICME) to support optimized life-cycle design of materials and components in turbine engines. Benefits of this approach appear to include substantial improvements in model accuracy, coupled with reduced requirements for materials testing, potentially leading to a significant reduction in the time and cost to develop, validate, transition, and implement new, more fatigue resistant alloys. Published by Elsevier Ltd.

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Section: Life Limits and Competing-mode Of Fatiguementioning

confidence: 99%

Reducing uncertainty in fatigue life limits of turbine engine alloys

Larsen

Jha

Szczepanski

et al. 2013

International Journal of Fatigue

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“…To that end, life-limiting mechanisms of superalloys have received considerable attention [12,14,20,23,24,27,30,31]. This is because superalloy applications such as in aircraft gas turbine applications demand a very low probability of failure.…”

Section: Introductionmentioning

confidence: 99%

“…The processes of fatigue crack formation and early growth from surface grains, inclusions, or pores and bulk inclusions govern the scatter within the life-limiting and mean-controlling datasets [27]. Statistically-speaking, the weighting parameters p s and p b are the respective probabilities that a given data point belongs to the life-limiting dataset (first term) or the mean-controlling dataset (second term).…”

Section: Introductionmentioning

confidence: 99%

“…Physically-based life prediction methodologies that integrate the mechanisms of fatigue variability in Ni-base superalloys are of great interest in life-extension as well as in new alloy development in the gas turbine industry [27][28][29]. To that end, life-limiting mechanisms of superalloys have received considerable attention [12,14,20,23,24,27,30,31].…”

Section: Introductionmentioning

confidence: 99%

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Microstructure-sensitive weighted probability approach for modeling surface to bulk transition of high cycle fatigue failures dominated by primary inclusions

Salajegheh

2014

International Journal of Fatigue

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“…solvus of approximately 1124 degrees C, making it an ideal alloy for comparing the effects of heat treatment on phase evolution with other third generation nickel base superalloys [29,30].…”

Section: Introductionmentioning

confidence: 99%

Determination of Gamma-Prime Site Occupancies in Nickel Superalloys Using Atom Probe Tomography and X-Ray Diffraction (Preprint)

Tiley¹,

Senkov²,

Viswanathan³

et al. 2012

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The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information SPONSORING/MONITORING AGENCY REPORT NUMBER(S)AFRL-RX-WP-TP-2012-0390 DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution unlimited. Preprint to be submitted to Metallurgical and Materials Transactions. SUPPLEMENTARY NOTESThe U.S. Government is joint author of this work and has the right to use, modify, reproduce, release, perform, display, or disclose the work. PA Case Number and clearance date: 88ABW-2012-2970, 21 May 2012. This document contains color. ABSTRACTRene88 samples were investigated using atom probe tomography and x-ray diffraction using a monochromated synchrotron beam with different energy values to determine the preferred site occupancy of various alloying elements within the ordered γ' precipitates. Samples were solutionized and cooled at 24 degree C/min with subsequent aging at 760 degrees C. The synchrotron-based x-ray diffraction results indicate that niobium prefers to reside on the aluminum sublattice site of the γ' phase. Additionally, the experimental results also indicate that chromium prefers the nickel sublattice sites while cobalt is likely to occupy both the aluminum and nickel sublattice sites. The x-ray results on the chromium occupancy disagree with atom probe results from the same alloy that indicate that chromium prefers the aluminum sublattice sites. Modeling studies indicate cobalt has no strong site preference. SUBJECT TERMS AbstractRene88 samples were investigated using atom probe tomography and x-ray diffraction using a monochromated synchrotron beam with different energy values to determine the preferred site occupancy of various alloying elements within the ordered γ' precipitates. Samples were solutionized and cooled at 24 degree C/min with subsequent aging at 760 degrees C. The synchrotron-based x-ray diffraction results indicate that niobium prefers to reside on the aluminum sublattice site of the γ' phase. Additionally, the experimental results also indicate that chromium prefers the nickel sublattice sites while cobalt is likely to occupy both the aluminum and nickel sublattice sites. The x-ray results on the chromium occupancy disagree with atom probe results from the same alloy that indicate that chromium prefers the aluminum sublattice sites. Modeling studies indicate cobalt has no strong site preference.

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Microstructural Conditions Contributing to Fatigue Variability in P/M Nickel-Base Superalloys

Cited by 8 publications

References 9 publications

Reducing uncertainty in fatigue life limits of turbine engine alloys

Reducing uncertainty in fatigue life limits of turbine engine alloys

Microstructure-sensitive weighted probability approach for modeling surface to bulk transition of high cycle fatigue failures dominated by primary inclusions

Determination of Gamma-Prime Site Occupancies in Nickel Superalloys Using Atom Probe Tomography and X-Ray Diffraction (Preprint)

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