Creep Deformation Anisotropy in Single Crystal Superalloys

Caron, Pierre; Ohta, Yoshio; Nakagawa, Y. G.; Khan, T.

doi:10.7449/1988/superalloys_1988_215_224

Cited by 66 publications

(61 citation statements)

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“…Again, this is in accordance with results from Caron et al [30] where the c' size has no strong influence for temperatures between 980°C and 1050°C due to coarsening as a result of rafting perpendicular to the load direction. The LCF lifetime of the heat-treated SX CMSX-4 Ò SEBM specimens is superior to that of the heattreated cast material, whereas the as-built CMSX-4 Ò SEBM specimen failed much earlier than the respective heat-treated SEBM specimen.…”

Section: Creep Strengthsupporting

confidence: 82%

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Microstructure and Mechanical Properties of CMSX-4 Single Crystals Prepared by Additive Manufacturing

Körner

Ramsperger

Meid

et al. 2018

Metall Mater Trans A

128

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Currently, additive manufacturing (AM) experiences significant attention in nearly all industrial sectors. AM is already well established in fields such as medicine or spare part production. Nevertheless, processing of high-performance nickel-based superalloys and especially single crystalline alloys such as CMSX-4 Ò is challenging due to the difficulty of intense crack formation. Selective electron beam melting (SEBM) takes place at high process temperatures (~1000°C) and under vacuum conditions. Current work has demonstrated processing of CMSX-4 Ò without crack formation. In addition, by using appropriate AM scan strategies, even single crystals (SX SEBM CMSX-4 Ò ) develop directly from the powder bed. In this contribution, we investigate the mechanical properties of SX SEBM CMSX-4 Ò prepared by SEBM in the as-built condition and after heat treatment. The focus is on hardness, strength, low cycle fatigue, and creep properties. These properties are compared with conventional cast and heat-treated material.

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Section: Creep Strengthsupporting

confidence: 82%

“…After creep, the inhomogeneous c/c' microstructure of the as-built condition is still obvious. Caron et al [30] have shown that the c/c' size has a strong influence on creep properties for temperatures between 760°C and 850°C. Decreasing the c' size from 340 to 220 nm strongly reduces the time to fracture.…”

Section: Low Cycle Fatigue Strengthmentioning

confidence: 99%

Microstructure and Mechanical Properties of CMSX-4 Single Crystals Prepared by Additive Manufacturing

Körner

Ramsperger

Meid

et al. 2018

Metall Mater Trans A

128

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“…The basic pattern of orientation dependence is maintained over a wide range of alloy compositions, but the contribution of each of the components -nucleation, propagation and work-hardening -varies. This leads to immensely complex behaviour, for example: the / misfit and volume fraction affects the propagation of dislocations in the leading to accelerated or reduced work-hardening, Using this approach it is possible to rationalise the reversal in the orientation dependence of the [111] and [001] tensile axes through the effect of heat treatment in changing the volume fraction [3]. Cobalt and rhenium content affect superlattice stacking fault propagation through the two-phase structure, explaining the observation that some alloys appear to be unusually sensitive to the effects of orientation; others are very tolerant showing little primary creep over a wide range of orientations [8].…”

Section: Primary Creepmentioning

confidence: 99%

“…Work over many years has shown that the creep behaviour at low temperatures (750 C-850 C) is extraordinarily sensitive to changes in orientation, composition and the heat-treated microstructure [2,3,4,5,6,7,8], yet the mechanistic origins of these effects are not fully established. In this paper we are able to rationalise some of these effects by focussing on the nature of the processes occurring during primary and secondary creep, and in the transition period between the two.…”

Section: Introductionmentioning

confidence: 99%

Single Crystal Superalloys: The Transition from Primary to Secondary Creep

Drew¹,

Reed²,

Kakehi³

et al. 2004

Superalloys 2004 (Tenth International Symposium)

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In this paper we compare the effect of stress, orientation and alloy composition on primary and secondary creep rate in a number of single crystal alloys. The activation energies and stress dependence of primary and secondary creep, measured in the alloy CMSX-4, show a distinctive low activation energy associated with stacking fault shear during primary creep which disappears at low stress. Twostage creep tests show that a fully developed dislocation network, introduced into the microstructure by limited deformation at 950 C, results in a substantial drop in primary creep strain during subsequent testing at 750 C. Comparison with identically-oriented samples without prestrain confirms the role of dislocation networks in the channels as the major hardening mechanism and shows that secondary creep is unaffected by the pre-strain. These observations are inconsistent with existing understanding of the transition between primary and secondary creep in some important respects. We argue that the mechanisms producing primary and secondary creep strain are similar, but that the secondary creep rate is determined by the rate of formation of defects at the / interface. This enables many aspects of the dependence of creep rate on orientation, alloy composition and micro-structure to be rationalised.

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“…For this, further measures of the macroscopic deforma-͗112͘{111} slip, as indicated by the observation of stacking faults in interrupted tests and from the direction of rotation of the tensile axis during creep. [3,6,[8][9][10][11] Others argue that, although stacking faults are present during primary creep, they make little contribution to the strain. [12,13] The stacking faults and the high primary-creep strain disappear if the stress is lowered [13] triangle.…”

Section: Introductionmentioning

confidence: 97%

On the primary creep of CMSX-4 superalloy single crystals

Rae

Rist

Cox

et al. 2000

Metall Mater Trans A

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The effect of orientation on the primary-creep mechanism of the Ni-based single-crystal superalloy CMSX-4 is examined. Four specimens with orientations within 20 deg of the [001] axis are deformed at 750 ЊC and 750 MPa and show a decreasing amount of primary creep as the tensile axis approaches the [001]-[011] symmetry boundary. Of these, specimen N lies within 1 deg of [013] and shows a negligible primary creep and a very low secondary creep rate. For this specimen, direct observation in the transmission electron microscope (TEM) and analysis of the shape change show that ͗112͘{111}, stacking-fault shear, is absent. Analysis of the dislocations present in the gamma precipitates and at the ␥ /␥ Ј interface shows that the only dislocations present have the Burgers vectors a/2[101] and a/2[10-1], which cannot combine to nucleate the dislocations necessary for stacking-fault shear. Thus, it is argued that the reason for the low degree of primary creep for orientations close to the [001]-[011] symmetry boundary is not the interaction between two equally stressed ͗112͘{111} systems, but the lack of either. As the orientation moves away from the [001]-[011] boundary, the range of dislocation Burgers vectors increases and stacking-fault shear is nucleated; the amount of primary creep increases as a consequence.

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Creep Deformation Anisotropy in Single Crystal Superalloys

Cited by 66 publications

References 0 publications

Microstructure and Mechanical Properties of CMSX-4 Single Crystals Prepared by Additive Manufacturing

Microstructure and Mechanical Properties of CMSX-4 Single Crystals Prepared by Additive Manufacturing

Single Crystal Superalloys: The Transition from Primary to Secondary Creep

On the primary creep of CMSX-4 superalloy single crystals

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