The current status of controlled thermal expansion superalloys

Wanner, E.A.; DeAntonio, D.A.; Smith, DJ; Smith, J. S.

doi:10.1007/bf03220162

Cited by 11 publications

(5 citation statements)

References 4 publications

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“…This phase is observed at 940 °C, 960 °C, 980 °C, and 1000 °C with continuous, rod, partial dissolution, and complete dissolution morphologies, respectively. The absolute dissolution temperature of the laves phase in the T.T.T diagram of the IN909 superalloy (with approximately 0.2 more Si than the IN907 alloy) is 1040 °C [ 1 ]. The cause of the 40 °C reduction compared to the present IN907 alloy [ 16 , 17 ] is the effect of the Si value on the precipitate temperature range of this phase, which decreases its value to reduce the temperature range of this phase.…”

Section: Resultsmentioning

confidence: 99%

“…IN907 superalloy (UNS N19907) is a Fe–Ni–Co-based alloy known for its low thermal expansion coefficient, excellent resistance to hydrogen embrittlement, and high strength to a maximum temperature of 650 °C [ 1 ]. This superalloy is usually processed by thermomechanical processes and used in aerospace applications, including gas turbine engine components such as shells, seals, and rings [ 2 ].…”

Section: Introductionmentioning

confidence: 99%

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Experimental selection of the initial dissolution treatment temperature range for the subsequent cold rolling of IN907 superalloy sheet

Sangetabi

Abbasi

Mahdavi

2022

Heliyon

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental selection of the initial dissolution treatment temperature range for the subsequent cold rolling of IN907 superalloy sheet

Sangetabi

Abbasi

Mahdavi

2022

Heliyon

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“…In alloy 909, however, the presence of the Laves phase assists during thermomechanical processing to improve grain control via restricting grain growth. [7][8][9][10][11] Several investigations are present in the literature on the ageing and overaging characteristics of alloy 909. [4][5][6][7][12][13][14] The recommended aging heat treatment for the alloy by Special Metals Co. is heat and hold at 718uC for 8 h, furnace cool to 621uC for 8 h, air cool.…”

Section: Introductionmentioning

confidence: 99%

Microstructure characterisation of solution treated (ST) and solution treated and aged (STA) Incoloy 909

Balachander

Vishwakarma

Tang

et al. 2011

Materials Science and Technology

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A microstructural analysis has been carried out on the commercially solution treated and aged (STA) Incoloy 909 superalloy to evaluate the phases present using optical, SEM, TEM and differential scanning calorimetry. Comparison is made where possible with non-standard STA analyses reported in the literature. In the STA condition, the main phase present besides the γ matrix was a deliberately produced Laves phase to control grain growth. Increasing the solution temperature above that recommended for the alloy resulted in eventual solution of the Laves phase and concomitant grain growth. In the STA condition, in addition to the Laves phase, a copious precipitation of a γ′ phase (Ni3TiNb) was observed. In addition, a limited observation was made of the early stages of the transition of some of the γ′ phase to the ϵ phase for the over aged condition. There was no ϵ phase observed in the STA condition. A final observation was the presence of ‘black grain’ previously reported in the literature, in both the ST and STA conditions in the authors’ research. The present view is that the phenomenon is an etching artefact and not a genuine microstructural feature.

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“…27,28 The oxidation resistance of binary Fe-Ni alloys has been studied at high temperatures ͑generally Ͼ800°C͒, which was found to improve with an increase in Ni content. 29,30 Based on the consideration of thermal expansion behavior and oxidation resistance, the Fe-Ni alloy system might offer some unique potentials as the interconnect of intermediate temperature SOFC.…”

mentioning

confidence: 99%

“…The Fe-Ni alloys such as the Fe-36 wt % Ni alloy ͑i.e., Fe-36Ni; all the alloy compositions are given in wt % in this paper͒ have been employed as a compositional basis for the development of a series of low thermal expansion superalloys such as Alloy 52, Alloy 48 and Incoloy 900 series, for applications such as glass-tometal sealing materials due to the Invar effect. 27,28 The oxidation resistance of binary Fe-Ni alloys has been studied at high temperatures ͑generally Ͼ800°C͒, which was found to improve with an increase in Ni content. 29,30 Based on the consideration of thermal expansion behavior and oxidation resistance, the Fe-Ni alloy system might offer some unique potentials as the interconnect of intermediate temperature SOFC.…”

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confidence: 99%

Evaluation of Binary Fe–Ni Alloys as Intermediate-Temperature SOFC Interconnect

Zhu

Geng

et al. 2007

J. Electrochem. Soc.

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Binary Fe-Ni alloys with 45-60Ni ͑wt %͒ were evaluated as an interconnect material for intermediate-temperature solid oxide fuel cells ͑SOFCs͒. The oxidation resistance of the Fe-Ni alloys in air improved with increasing Ni content. The thermally grown oxide scale on these alloys generally consisted of a Fe 2 O 3 top layer and a ͑Fe,Ni͒ 3 O 4 spinel inner layer, with the thickness of the Fe 2 O 3 layer decreasing as the Ni content increased. No measurable weight change was observed after isothermal oxidation in Ar + 4%H 2 + 3%H 2 O at 800°C and a metallic surface was maintained. The coefficient of thermal expansion ͑CTE͒ increased with the Ni content in these alloys and the CTE values were similar to those of other cell components. The ͑Fe,Ni͒ 3 O 4 spinel with a composition similar to that thermally grown on the Fe-50Ni alloy exhibited a CTE value close to the alloy substrate, which aids scale spallation resistance for this alloy. The scale area specific resistance of the Fe-Ni alloys was found to be comparable to that of the current interconnect alloys, as a result of high electrical conductivity of the ͑Fe,Ni͒ 3 O 4 spinel. The promise and issue with these Fe-Ni alloys as interconnect materials are highlighted and potential approaches to address the issue are outlined.Some major technical challenges such as cost-effective manufacturing and long-term reliability of the stack must be overcome to advance the solid oxide fuel cell ͑SOFC͒ technology to commercial reality. One of these critical issues is the development of a suitable interconnect material that provides electrical series connection of individual single cells and gas impermeability to separate fuel and oxidant gases. A significant advance in the development of intermediate-temperature SOFCs has been the use of metallic alloys as the interconnect material. 1-10 For SOFC interconnect application, the metallic alloys must develop an electrically conductive, oxidation-resistant oxide scale in the SOFC operating environments. From this point of view, only Cr 2 O 3 -forming alloys are suitable for SOFC interconnect application because Cr 2 O 3 possesses adequate electrical conductivity under SOFC working conditions, whereas the other two protective oxides, SiO 2 and Al 2 O 3 , are electrically insulating. 6,11 However, the Cr 2 O 3 -forming alloys have an inherent weakness that is the formation of volatile Cr͑VI͒ species due to Cr evaporation, especially in the presence of water vapor. The volatile Cr͑VI͒ species might migrate to and poison the cathode, leading to the decreased electrochemical activity of the cathode and subsequent degradation in stack performance over long-term operation. [12][13][14][15][16] Formation of electrically conductive, low Cr-volatility surface oxides on metallic substrates is highly desired to reduce the Cr volatilization of the Cr-containing interconnect alloys. Currently, two approaches are being taken to achieve such a surface oxide layer. The first one is the development of some low Cr-volatility surface coatings such as La...

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The current status of controlled thermal expansion superalloys

Cited by 11 publications

References 4 publications

Experimental selection of the initial dissolution treatment temperature range for the subsequent cold rolling of IN907 superalloy sheet

Experimental selection of the initial dissolution treatment temperature range for the subsequent cold rolling of IN907 superalloy sheet

Microstructure characterisation of solution treated (ST) and solution treated and aged (STA) Incoloy 909

Evaluation of Binary Fe–Ni Alloys as Intermediate-Temperature SOFC Interconnect

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