Effect of thermal exposure on the stress-rupture life and microstructure of a low Re-containing single crystal alloy

Zhang, Heng; Liang, Yunfei; Ru, Yi; Li, Shusuo; Zhou, Jian; Gong, Shengkai

doi:10.1016/j.pnsc.2015.01.010

Cited by 12 publications

(1 citation statement)

References 21 publications

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“…During high-temperature service, the γ/γ' dual-phase microstructure will be degraded due to the coarsening process, which can lead to the degradation of mechanical properties. For example, long-term thermal exposure can cause γ' precipitates and γ matrix in superalloys to coarsen [9,10] . Meanwhile long-term thermal exposure contributes to the precipitation of secondary TCP (topological close-packed) phases, such as µ phase, P phase.…”

Section: Effect Of Long-term Thermal Exposure On Microstructure and Creep Properties Of Dd5 Single Crystal Superalloymentioning

confidence: 99%

Effect of long-term thermal exposure on microstructure and creep properties of DD5 single crystal superalloy

et al. 2021

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Nickel-based single crystal superalloys are widely employed for hot sections of aircraft engines and gas turbines because of their excellent high temperature creep and fatigue strengths [1][2][3] . Single crystal superalloys are strengthened by high volume fractions of cubical γ' phase embedded coherently in γ matrix phase, and by the addition of a variety of refractory elements [4,5] , such as Re, W and Mo. The addition of refractory elements with higher melting points can enhance the solid solution strengthening and creep properties, but meanwhile, the freckles and precipitation of harmful phases may occur [6] . Adding a small amount of C element may form carbides, which can consume heavy refractory elements to reduce the probability of freckles and harmful phases formation [7,8] .

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Section: Effect Of Long-term Thermal Exposure On Microstructure and Creep Properties Of Dd5 Single Crystal Superalloymentioning

confidence: 99%

Effect of long-term thermal exposure on microstructure and creep properties of DD5 single crystal superalloy

et al. 2021

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Influence of thermal exposure on microstructure and stress rupture properties of a new Re-containing single crystal Ni-based superalloy

et al. 2018

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S ingle-crystal (SC) nickel-based superalloys are widely used as turbine blade materials because of their excellent mechanical properties [1] . The superior high-temperature behavior is mainly attributed to the two-phase microstructure consisting of a γ-matrix (Ni) and a large volume fraction of γ′-precipitates (Ni 3 Al) in the range of 65% to 70%. Within this optimum γ′ volume fraction range, the strengthening effect of the γ′-precipitates depends largely on their size and morphology [2][3][4] . During high-temperature service, the γ/γ′ two-phase microstructure will be degraded due to a coarsening process, during which the γ′ precipitates evolve from cuboidal into plate-like morphology, accompanied by a loss of the precipitate coherency and deterioration Abstract: In this study, the long-term thermal microstructural stability and related stress rupture lives of a new Re-containing Ni-based single-crystal superalloy, DD11, were investigated after high-temperature exposure for different lengths of time. The results show that the γ' precipitates retained a cuboidal morphology and the γ' size increased after short thermal exposure for 50 h at 1,070 °C. As the thermal exposure time was prolonged to 500 h, the cuboidal γ' gradually changed into irregular raft-like morphology due to particles coalescence, and the morphology of the microstructure was almost unchanged after further thermal exposure up to 3,000 h. The stress rupture experiments at 1,070 °C and a tensile stress of 140 MPa showed that the rupture lives increased significantly after thermal exposure for 50 h and dropped dramatically with increasing exposure time up to 500 h but decreased slowly after exposure for more than 500 h. These results imply that stress rupture properties did not decrease when the γ' remained cuboidal but degraded to different extents during the γ' coarsening process. The coarsening of the γ' precipitates and change in morphology were regarded as the main factors leading to the degradation of the stress rupture lives. This study provides fundamental information on the high-temperature longterm microstructural stability and mechanical performance, which will be of great help for DD11 alloy optimization and engineering aeroengine applications.Key words: Ni-based superalloy; thermal exposure; microstructure; coarsening; stress-rupture properties of the mechanical properties [5,6] . The driving forces for coarsening are the reduction of the γ/γ′ interfacial area, the decrease of the lattice mismatch strain, and reduction of the modulus misfit [7,8] . The γ′ coarsening process is strongly affected by service temperature and time and vary with compositional differences in Ni-based superalloys due to the diffusion-related coarsening process. Since single-crystal blades and vanes work for a long time at elevated temperatures during service, a reliable mechanical performance is essential for engineering application as gas turbine blades. Consequently, the stability of the microstructure and mechanical properties after long-term exposure at e...

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Effect of applied stress on γ’-rafting behavior in a Ni-based single-crystal superalloy: experiments and finite element analysis

Shang

et al. 2018

J. Iron Steel Res. Int.

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Effect of thermal exposure on the stress-rupture life and microstructure of a low Re-containing single crystal alloy

Cited by 12 publications

References 21 publications

Effect of long-term thermal exposure on microstructure and creep properties of DD5 single crystal superalloy

Effect of long-term thermal exposure on microstructure and creep properties of DD5 single crystal superalloy

Influence of thermal exposure on microstructure and stress rupture properties of a new Re-containing single crystal Ni-based superalloy

Effect of applied stress on γ’-rafting behavior in a Ni-based single-crystal superalloy: experiments and finite element analysis

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