Fatigue resistance of the grain size transition zone in a dual microstructure superalloy disk

Gabb, Timothy P.; Kantzos, Pete; Telesman, Jack; Gayda, John; Sudbrack, Chantal K.; Palsa, B. S.

doi:10.1016/j.ijfatigue.2010.09.022

Cited by 66 publications

(36 citation statements)

References 11 publications

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“…Based on existing research carried out at NASA, it has been found that the LSHR alloy possesses exceptional high temperature tensile strength and creep resistance [6]. It is also claimed that the LSHR alloy has good processing versatility due to the low γʹ solvus temperature, which makes it possible to produce a dual microstructure turbine disc with optimized creep and fatigue performance at various disc locations by differentiated heat treatments [6,9,10].…”

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confidence: 99%

“…Studying low cycle fatigue (LCF) performance at elevated temperatures indicates that the typical fatigue-initiation sites and the overall fatigue life of LSHR alloy are related to the microstructures, test temperatures and strain ranges employed [6,10]. Specifically, cracks mainly initiate from internal inclusions and/or pores and occasionally initiate from crystallographic facets in FG LSHR at elevated temperatures (427 o C and 704 o C).…”

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confidence: 99%

“…This has been observed when the applied total strain is less than 0.8% (which is usually associated with longer fatigue life). Whereas cracks predominantly initiate from crystallographic facets of larger grains in the CG LSHR variant, which usually produces a shorter fatigue life at similar moderate strain ranges [10]. When higher strain ranges were applied by conducting LCF tests at higher temperature (704 o C), an oxidation assisted crack initiation process was observed to come into effect, usually forming intergranular cracks, especially when a long dwell time was applied at the peak time during LCF tests [6].…”

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Effects of microstructures on fatigue crack initiation and short crack propagation at room temperature in an advanced disc superalloy

Jiang

Karpasitis

Gao

et al. 2015

Materials Science and Engineering: A

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Fatigue crack initiation and early short crack propagation behaviour in two microstructural variants of a recently developed Low Solvus, High Refractory (LSHR) disc superalloy at room temperature has been investigated by three-point bending with replication procedure.The results shows that fine gained (FG) LSHR possesses higher fatigue life due to its better crack initiation resistance, limited crack coalescence and comparable Stage I crack propagation resistance to the coarse grained (CG) LSHR, although its resistance to Stage II crack propagation is inferior. Twin boundary (TB) cracking in the relatively large grains dominates the crack initiation process along with occasional crack initiation due to slip band cracking. Activation of the primary slip systems parallel to the TB at matrix and twin and high resolved shear stress associated with high Schmid factor (SF) are required for TB crack initiation. Cracks preferentially propagate along slip bands associated with high SF slip systems after initiation. But cracks also propagate along slip bands associated with slip systems with lower SF if the inclination angle between the slip band ahead of the crack tip and the crack segment of the crack tip is small enough to enable a steady transition (or nondeflected growth) of cracks across the grain boundary.

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Effects of microstructures on fatigue crack initiation and short crack propagation at room temperature in an advanced disc superalloy

Jiang

Karpasitis

Gao

et al. 2015

Materials Science and Engineering: A

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“…The mean fatigue lives could be compared assuming a log normal distribution, as is evident by the linear fit of the data shown in a plot with a logarithmic life cycle axis. No difference was consistently observed between strain-controlled and loadcontrolled test lives [11]. The resulting lives were therefore grouped together in all analyses.…”

Section: Low Cycle Fatigue Responsementioning

confidence: 99%

“…ALA grain size as determined according to ASTM E930 could be used as a simple, well established measurement for bounding fatigue life in such conditions [17]. ALA grain size could then correlate reasonably well with fatigue life at each temperature, and could be used as a practical predictor for upper bounds of facet grain size [11]. Here, it should be understood that facet size will approach but often be smaller than actual ALA size for each disk and specimen location.…”

Section: Notch Failure Modesmentioning

confidence: 99%

Fatigue Failure Modes of the Grain Size Transition Zone in a Dual Microstructure Disk

Gabb¹,

Kantzos²,

Palsa³

et al. 2012

Superalloys 2012 (Twelfth International Symposium)

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Mechanical property requirements vary with location in nickelbased superalloy disks. In order to maximize the associated mechanical properties, heat treatment methods have been developed for producing tailored grain microstructures. In this study, fatigue failure modes of a grain size transition zone in a dual microstructure disk were evaluated. A specialized heat treatment method was applied to produce varying grain microstructure in the bore to rim portions of a powder metallurgy processed nickel-based superalloy disk. The transition in grain size was concentrated in a zone of the disk web, between the bore and rim. Specimens were extracted parallel and transversely across this transition zone, and multiple fatigue tests were performed at 427 °C and 704 °C. Grain size distributions were characterized in the specimens, and related to operative failure initiation modes. Mean fatigue life decreased with increasing maximum grain size, going out through the transition zone. The scatter in limited tests of replicates was comparable for failures of uniform gage specimens in all transition zone locations examined.

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Nondestructive Evaluation of Microstructure in Super Alloy Disk Material

Blackshire

Medina

2011

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Fatigue resistance of the grain size transition zone in a dual microstructure superalloy disk

Cited by 66 publications

References 11 publications

Effects of microstructures on fatigue crack initiation and short crack propagation at room temperature in an advanced disc superalloy

Effects of microstructures on fatigue crack initiation and short crack propagation at room temperature in an advanced disc superalloy

Fatigue Failure Modes of the Grain Size Transition Zone in a Dual Microstructure Disk

Nondestructive Evaluation of Microstructure in Super Alloy Disk Material

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