A study of fatigue damage mechanisms in Waspaloy from 25 to 800°C

Lerch, Bradley A.; Jayaraman, N.; Antolovich, Stephen D.

doi:10.1016/0025-5416(84)90177-0

Cited by 144 publications

(70 citation statements)

References 9 publications

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“…At room temperature, fatigue cracks have been found to initiate from slip bands [8,9,10,11], twin boundaries [10], grain boundaries [12], at carbides [13], due to cracking of inclusions/precipitates [2], or at other features from materials processing, such as pores [14]. The small fatigue cracks that are formed immediately after initiation tend to exhibit anomalously high, irregular growth rates when compared to large cracks at similar ΔK [2,15,16].…”

Section: Introductionmentioning

confidence: 99%

Effects of microstructure on room temperature fatigue crack initiation and short crack propagation in Udimet 720Li Ni-base superalloy

Pang

Reed

2008

International Journal of Fatigue

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An assessment of the effects of microstructure on room temperature fatigue crack initiation and short crack propagation in a Ni-base superalloy is presented. The assessment was carried out on microstructural variants of U720Li, including as-received U720Li, U720Li-LG (large grain variant) and U720Li-LP (large intragranular coherent γ′ variant). Fatigue tests were carried out at room temperature using a 20Hz sinusoidal cycling waveform on plain bend bars. Tests were conducted in 3-point bend under load control with an R-ratio of 0.1. A maximum load of 95% σ y was used in all tests. Room temperature fatigue crack initiation was noted to occur due to slip band cracking and from porosity on or just beneath the surface in all materials. Crack propagation was noted to be highly faceted (due to planar slip band cracking) immediately after crack initiation followed by a transition to a flatter Stage II type crack path as crack length increases.U720Li-LP was noted to show the longest fatigue lifetime, followed by U720Li-LG while U720Li shows the shortest life. The longer lifetime of U720Li-LP was linked to a higher resistance to both fatigue crack initiation and short crack propagation. U720Li and U720Li-LG show approximately similar crack initiation resistance although U720Li-LG showed slightly improved short crack growth resistance. The observations have been rationalised in terms of the microstructural characteristics of the materials, and it is believed that larger grain size, larger coherent γ′ precipitate size and higher volume fractions of both coherent and primary γ′ precipitates will improve overall fatigue * Now at Dept. of Materials Science & Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ, UK lifetimes in PM Ni-base alloys which exhibit planar slip characteristics at room temperature.

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Section: Introductionmentioning

confidence: 99%

Effects of microstructure on room temperature fatigue crack initiation and short crack propagation in Udimet 720Li Ni-base superalloy

Pang

Reed

2008

International Journal of Fatigue

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“…Further experimental details will be given elsewhere (19). It has been well documented that gamma -prime-strengthened, Ni -base superalloys are subject to the development of concentrated, planar slip bands during LCF (20,21,22). The gamma-prime precipitates are sheared by such bands, causing a transition to coarse, planar slip (14).…”

Section: Methodsmentioning

confidence: 99%

Oxide Dispersion Strengthened Superalloys: The Role of Grain Structure and Dispersion During High Temperature Low Cycle Fatigue

Elzey¹,

Arzt²

1988

Superalloys 1988 (Sixth International Symposium)

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The mechanisms leading to failure during high temperature, LCF and creep-fatigue are presented and discussed for two representative, commercial ODS (Oxide DispersionStrengthened) superalloys, Inconel MA 754 and MA 6000. The fatigue behavior of these alloys is compared with that of conventional (non-ODS) superalloys of nearly identical elemental composition. The behavioral differences may be understood on the basis of the two primary microstructural differences between ODS and non-ODS, namely, grain structure and the fine particle dispersion itself. It is found that recrystallization defects in the form of fine grains are the primary cause of crack initiation in the ODS materials. The results are discussed in light of previous creep and fatigue studies of dispersion-strengthened alloys. Superalloys 1988

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“…Based on TEM evidence, they assumed that the critical step in yielding was to drive the dislocation into the ordered precipitate to create APBE. The result was Grain size was 125 µm (ASTM 3) and the γ precipitates were 5-8 nm [19].…”

Section: Monotonic Deformation Of Ni-base Superalloysmentioning

confidence: 98%

“…In (b), the dark-field image was formed using a carbide reflection and shows dynamic precipitation of carbides on slip bands. The relative rotation between (a) and (b) is due to a difference in magnification in the bright-and dark-field images [19,36].…”

Section: Cyclic Deformation Of Ni-base Superalloysmentioning

confidence: 99%

“…In a study of Waspaloy, cyclically deformed over a range of temperatures, one important observation was a kind of dynamic strain ageing in which carbides precipitated upon newly formed slip bands as well as on existing grain boundaries (figure 14) [19,36]. An additional driving force for the formation of carbides is the reduction in strain energy associated with dislocations.…”

Section: (I) Formation Of New Phasesmentioning

confidence: 99%

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Microstructural aspects of fatigue in Ni-base superalloys

Antolovich

2015

Phil. Trans. R. Soc. A.

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Nickel-base superalloys are primarily used as components in jet engines and land-based turbines. While compositionally complex, they are microstructurally simple, consisting of small (50–1000 nm diameter), ordered, coherent Ni 3 (Al,Ti)-type L1 2 or Ni 3 Nb-type DO 22 precipitates (called γ ′ and γ ′′ , respectively) embedded in an FCC substitutional solid solution consisting primarily of Ni and other elements which confer desired properties depending upon the application. The grain size may vary from as small as 2 μm for powder metallurgy alloys used in discs to single crystals the actual size of the component for turbine blades. The fatigue behaviour depends upon the microstructure, deformation mode, environment and cycle time. In many cases, it can be controlled or modified through small changes in composition which may dramatically change the mechanism of damage accumulation and the fatigue life. In this paper, the fundamental microstructural, compositional, environmental and deformation mode factors which affect fatigue behaviour are critically reviewed. Connections are made across a range of studies to provide more insight. Modern approaches are pointed out in which the wealth of available microstructural, deformation and damage information is used for computerized life prediction. The paper ends with a discussion of the very important and highly practical subject of thermo-mechanical fatigue (TMF). It is shown that physics-based modelling leads to significantly improved life prediction. Suggestions are made for moving forward on the critical subject of TMF life prediction in notched components.

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A study of fatigue damage mechanisms in Waspaloy from 25 to 800°C

Cited by 144 publications

References 9 publications

Effects of microstructure on room temperature fatigue crack initiation and short crack propagation in Udimet 720Li Ni-base superalloy

Effects of microstructure on room temperature fatigue crack initiation and short crack propagation in Udimet 720Li Ni-base superalloy

Oxide Dispersion Strengthened Superalloys: The Role of Grain Structure and Dispersion During High Temperature Low Cycle Fatigue

Microstructural aspects of fatigue in Ni-base superalloys

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