On the Mechanical Behavior of a New Single-Crystal Superalloy for Industrial Gas Turbine Applications

Sato, Atsushi; Moverare, Johan; Hasselqvist, Magnus; Reed, Roger C.

doi:10.1007/s11661-011-0995-2

Cited by 62 publications

(33 citation statements)

References 21 publications

(29 reference statements)

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“…solvus temperature of 1196ºC and a solidus temperature of 1318ºC [12]. These experimental observations were compared with thermodynamic calculations using Thermocalc [13] and a very good agreement was found, see Fig.3.…”

Section: Heat Treatmentmentioning

confidence: 56%

“…microstructure developed during primary ageing has been studied, since these need to be chosen carefully for optimised mechanical properties. The mechanical properties of several different microstructures have been verified by creep and fatigue testing [12,14]. Based on these observations the following heat treatment conditions are proposed for STAL-15:…”

Section: Heat Treatmentmentioning

confidence: 99%

“…A significant difference between CMSX-4 and the high Cr-alloys in terms of deformation behaviour during OP TMF testing has been noticed during the testing. Both alloys develop very localised deformation bands which extend across the entire cross-section of the specimen; moreover the fracture surface is normally purely crystallographic and occurs along one of the [12]. Note that first ageing condition for this specimen was 1120ºC for 24 hrs, followed by air cooling.…”

Section: Fatiguementioning

confidence: 99%

See 2 more Smart Citations

A New Single Crystal Superalloy for Power Generation Applications

Reed¹,

Moverare²,

Sato³

et al. 2012

Superalloys 2012 (Twelfth International Symposium)

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The properties of a newly developed single crystal superalloyknown as STAL-15 -is described which is suitable for use in first stage blades of industrial gas turbines (IGTs). With 15 wt.% Cr and 4.55 wt.% Al, the alloy combines good corrosion and oxidation resistance with sufficient creep and fatigue performance. Traditionally, polycrystalline alloys such as IN792 and IN738LC or the single crystal alloy PWA-1483 have been used for this application; unfortunately they display only limited resistance to environmental degradation. The new alloy does not display this weakness and is therefore highly optimised for IGT applications. The new alloy is shown to be an alumina (Al2O3) former; the mechanisms behind the Al2O3-formation process are studied and the effects arising from changes in the chemical composition have been modelled. In addition, the mechanical properties in terms of creep and fatigue resistance are demonstrated together and the alloy stability evaluated during long term (up to 10,000 hours) exposure. For such applications, the new alloy is superior to existing nickel-based single crystal superalloys designed for aeroengine applications and which are optimised for very high creep resistance. The absence of Re contributes to a lower cost of alloy stock, and enhanced castability.

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Section: Heat Treatmentmentioning

confidence: 56%

Section: Heat Treatmentmentioning

confidence: 99%

Section: Fatiguementioning

confidence: 99%

See 1 more Smart Citation

A New Single Crystal Superalloy for Power Generation Applications

Reed¹,

Moverare²,

Sato³

et al. 2012

Superalloys 2012 (Twelfth International Symposium)

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“…Elastic anisotropy due to the rafting phenomenon can also occur, and this anisotropy is increased with increased temperature. For example, studies show that the elastic anisotropy factor E [100] /E [001] in-creases up to 1.010-1.025 at temperatures of 1000°C [33]. Research also shows that the stiffness strongly decreases with increased temperature [34].…”

Section: Elasticitymentioning

confidence: 99%

“…In such cases the crack propagation starts at the twin intersections and propagates (with help from oxidation) along twin plates already from the surface. It seems that twinning during TMF cycling, is a compressive stress phenomenon rather than a tensile one, see [91,100,101]. According to [101], a tension/compression asymmetry of the twinning behaviour is prevalent during the intermediate stage of TMF cycling, since the force needed to create a twin in tension is significantly larger than in compression.…”

Section: Thermomechanical Fatigue: a Literature Reviewmentioning

confidence: 99%

On Thermomechanical Fatigue of Single-Crystal Superalloys

Segersäll¹

2014

Linköping Studies in Science and Technology. Dissertations

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Thesis cover: Design by Maria J. SegersällPrinted by: LiU-Tryck, Linköping, Sweden, 2014 ISBN 978-91-7519-211-6 ISSN 0345-7524 Distributed by: Division of Engineering Materials, Department of Management and Engineering Linköping University SE-58183, Linköping, Sweden © 2014 Mikael SegersällThis document was prepared with L A T E X, October 17, 2014 AbstractThanks to their excellent mechanical and chemical properties at temperatures up to 1000°C, nickel-based superalloys are used in critical components in high-temperature applications such as gas turbines and aero engines. One of the most critical components in a gas turbine is the turbine blade, and to improve the creep and fatigue properties of this component, it is sometimes cast in single-crystal form rather than in the more conventional polycrystalline form. Gas turbines are most commonly used for power generation and the turbine efficiency is highly dependent on the performance of the superalloys.Today, many gas turbines are used as a complement for renewable energy sources, for example when the wind is not blowing or when the sun is not shining, which means that the turbine runs differently compared to earlier, when it ran for longer time periods with a lower number of start-ups and shutdowns. This new way of running the turbine, with an increased number of start-ups and shut-downs, results in new conditions for critical components, and one way to simulate these conditions is to perform thermomechanical fatigue (TMF) testing in the laboratory. During TMF, both mechanical strain and temperature are cycled at the same time, and one fatigue cycle corresponds to the conditions experienced by the turbine blade during one start-up and shut-down of the turbine engine.In the work leading to this PhD thesis, TMF testing of single-crystal superalloys was first performed in the laboratory and this was then followed microstructure investigations to study the occurring deformation and damage mechanisms. Specimens with different crystallographic directions have been tested in order to investigate the anisotropic behaviour shown by these materials. Results show a significant orientation dependence during TMF in which specimens with a low elastic stiffness perform better. However, it is also shown that specimens with a higher number of active slip systems perform better during TMF compared to specimens with less active slip sysiii tems. This is because a higher number of active slip systems results in a more widespread deformation and seems to be beneficial for the TMF life. Further, microscopy shows that the deformation during TMF is localised to several deformation bands and that different deformation and damage mechanisms prevail according to in which crystal orientation the material is loaded. Deformation twinning is shown to be a major deformation mechanism during TMF and the interception of twins seems to trigger recrystallization. This is certainly negative for the mechanical properties of single-crystal superalloys since no grain boundary strengthening elemen...

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