Microstructural evolution and compressive deformation of a new Ni–Fe base superalloy after long term thermal exposure at 700 °C

A low-cost, high-creep strength wrought Fe‒Ni-base superalloy for 700 °C advanced ultra-supercritical coal-fired power plant applications has been developed. The microstructural stability of this alloy during long-term exposures at 700 °C‒750 °C for up to 10000 h was investigated by SEM and TEM. The correlation between the microstructure evolution and the mechanical properties was studied. The experimental results showed that the major precipitates in the alloy were spherical γ′, MC and discrete M23C6 after the long-term exposure at 700 °C and 750 °C and no harmful phases, such as σ phase and η phase, were observed. The amount of M23C6 increased with exposure time at 700 °C while it decreased at 750 °C. During thermal exposure γ′ coarsened with increasing the exposure time and exposure temperature. Alloy showed good oxidation resistance due to the formation of external layer of Cr2O3. The yield strength of the alloy increased at first and then decreased with increasing exposure time at 700 °C, but it decreased gradually with increasing exposure time at 750 °C. The relationship between yield strength and the dominant deformation mechanisms of the alloy was discussed.

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Influence of thermal exposure on the microstructural evolution and mechanical properties of a wrought Ni-base superalloy

Materials Science and Engineering A ◽

10.1016/j.msea.2013.11.031 ◽

2014 ◽

Vol 593 ◽

pp. 55-63 ◽

Cited By ~ 39

Author(s):

I.S. Kim ◽

B.G. Choi ◽

H.U. Hong ◽

J. Do ◽

C.Y. Jo

Keyword(s):

Mechanical Properties ◽

Microstructural Evolution ◽

Thermal Exposure ◽

Base Superalloy

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Microstructural evolution and its influence on the impact toughness of GH984G alloy during long-term thermal exposure

Journal of Material Science and Technology ◽

10.1016/j.jmst.2020.06.005 ◽

2021 ◽

Vol 60 ◽

pp. 61-69 ◽

Cited By ~ 1

Author(s):

Yunsheng Wu ◽

Xuezhi Qin ◽

Changshuai Wang ◽

Lanzhang Zhou

Keyword(s):

Impact Toughness ◽

Microstructural Evolution ◽

Thermal Exposure ◽

The Impact

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Coarsening Behavior of Precipitates in a Conventional Cast Nickel Base Superalloy during Long Term Thermal Exposure

Materials Science Forum ◽

10.4028/www.scientific.net/msf.788.452 ◽

2014 ◽

Vol 788 ◽

pp. 452-458

Author(s):

Qiang Zeng ◽

Ping Yan ◽

Jing Chen Zhao ◽

Long Fei Zhang ◽

Lian Li

Keyword(s):

Aging Time ◽

Early Stage ◽

Aging Treatment ◽

Thermal Exposure ◽

Nickel Base Superalloy ◽

Coarsening Behavior ◽

Nickel Base ◽

The One ◽

Base Superalloy

A long term aging treatment at 900oC for 3000h was carried out on a conventional cast nickel base superalloy with standard solution and aging treatment. The microstructural evolution including the phases within grains and at grain boundaries (GBs) during thermal exposure in the alloy was observed using OM and SEM. It was shown that the major phases in the alloy after standard heat treatment were γ' precipitates and coarse blocky MC carbides, both of which were distributed not only within grains but also at GBs. During aging, the size of MC carbides and γ' precipitates both within grains and at GBs increased with increasing aging time. It was found that two characteristics of MC carbide and γ' precipitates evolved with aging time: the one is that the coarsening ratio of carbides and γ' precipitates at GBs were significantly higher than that of carbide and γ' precipitates inside the grains; the other is that the coarsening ratio of carbides was markedly higher than that of γ' precipitates. M6C carbide and η phase initially formed in the edge of MC carbide at the expense of MC carbides and γ' precipitates in the vicinity of MC during the early stage of aging. After 3000h, MC carbides inside the grains were covered by η phase films, while those distributed at GBs were completely decomposed into η phase and M6C particles.

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