Grain size effects in a Ni-based turbine disc alloy in the time and cycle dependent crack growth regimes

Jiang, Rong; Everitt, Stewart; Lewandowski, M.; Gao, Nong; Reed, P.A.S.

doi:10.1016/j.ijfatigue.2013.07.014

Cited by 89 publications

(82 citation statements)

References 25 publications

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“…1 and 2) indicate that the formation of a bulged oxide complex occurs prior to GB cracking. In addition, the observed layered oxide intrusion ahead of a propagating crack tip in a similar disc alloy RR1000 and the intact oxide tip along with cracked oxide wake which was found at a secondary crack tip in the LSHR alloy (by metallographic sectioning the fracture surface after long fatigue crack growth test) further verify that GB oxidation occurs prior to GB cracking [7,18].…”

Section: Discussionmentioning

confidence: 61%

Influence of orientation-dependent grain boundary oxidation on fatigue cracking behaviour in an advanced Ni-based superalloy

2015

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Fatigue tests have been conducted on an advanced disc Ni-based superalloy (Low Solvus, High Refractory (LSHR) alloy) at 650 o C in air under three-point bend loading to investigate the role of orientation-dependent grain boundary oxidation in crack initiation and early propagation. It is found that crack initiation occurs mainly from bulged grain boundary oxides, and cracks then predominantly propagate along the oxidised grain boundaries. These bulged oxides are extremely enriched in Co and preferentially form at the boundaries between high and low Schmid factor grains which are inclined normal to the applied tensile stress direction. Meanwhile, relatively flat/thin Ni/Ti/Al-rich oxide complexes also form at other grain boundaries, but they appear to be much less detrimental in fatigue crack initiation and propagation compared with the grain boundary bulged Co-rich oxide complexes.

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Section: Discussionmentioning

confidence: 61%

Influence of orientation-dependent grain boundary oxidation on fatigue cracking behaviour in an advanced Ni-based superalloy

2015

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“…Specimens used for the short crack tests were extracted from a turbine disc which was fabricated by canning atomized LSHR alloy powder followed by hot isostatically pressing, extruding and isothermally forging. The extracted specimens were supersolvus heat treated at 1171 o C and subsolvus heat treated at 1135 o C to yield CG and FG microstructures respectively, followed by the same dual aging heat treatments [4]. The obtained microstructures are shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

“…1, and the measured grain size and γ΄ size are shown in Table 1. The details of microstructure evaluation can be found in our previous publication [4]. …”

Section: Methodsmentioning

confidence: 99%

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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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“…While a coarser-grained microstructure resulting from a supersolvus heat treatment has been demonstrated to be beneficial-for example by comparing the behavior of any given alloy to sub-solvus and super-solvus processing [9,32,[34][35][36] -so far, grain size has not been varied independently of the c¢-precipitate size distribution. This gives rise to the question whether grain size independently improves environmentally-assisted crack growth resistance.…”

Section: B On the Role Of Grain Size-dependent Tougheningmentioning

confidence: 99%

On the Influence of Nb/Ti Ratio on Environmentally-Assisted Crack Growth in High-Strength Nickel-Based Superalloys

Németh

Crudden

Collins

et al. 2018

Metall Mater Trans A

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The effect of Nb/Ti ratio on environmentally-assisted crack growth of three prototype Ni-based superalloys is studied. For these alloys, the yield strength is unaltered with increasing Nb/Ti ratio due to an increase in grain size. This situation has allowed the rationalization of the factors influencing damage tolerance at 700°C. Primary intergranular cracks have been investigated using energy-dispersive X-ray spectroscopy in a scanning transmission electron microscope and the analysis of electron back-scatter diffraction patterns. Any possible detrimental effect of Nb on the observed crack tip damage due to Nb-rich oxide formation is not observed. Instead, evidence is presented to indicate that the tertiary c¢-precipitates are dissolving ahead of the crack consistent with the formation of oxides such as alumina and rutile. Our results have implications for alloy design efforts; at any given strength level, both more and less damage-tolerant variants of these alloys can be designed.

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Grain size effects in a Ni-based turbine disc alloy in the time and cycle dependent crack growth regimes

Cited by 89 publications

References 25 publications

Influence of orientation-dependent grain boundary oxidation on fatigue cracking behaviour in an advanced Ni-based superalloy

Influence of orientation-dependent grain boundary oxidation on fatigue cracking behaviour in an advanced Ni-based superalloy

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

On the Influence of Nb/Ti Ratio on Environmentally-Assisted Crack Growth in High-Strength Nickel-Based Superalloys

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