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Effects of short-term overloading or overheating during secondary creep on the creep behavior and microstructural evolution of the nickel-based single-crystal superalloy DD6.

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Title: Effects of short-term overloading or overheating during secondary creep on the creep behavior and microstructural evolution of the nickel-based single-crystal superalloy DD6.
Authors: Wang, Xiao1,2 (AUTHOR), Tan, Yidie1,2 (AUTHOR), Zhao, Jianjiang1,3 (AUTHOR), Wang, Fei1,3 (AUTHOR) wang.fei@zju.edu.cn, Chen, Yunmin1,3 (AUTHOR), Wei, Hua1,3 (AUTHOR) huawei@zju.edu.cn
Source: Journal of Materials Science. Aug2026, Vol. 61 Issue 30, p22361-22378. 18p.
Subjects: Microstructure, Dislocation structure, Turbine blades, Phase transitions, Nickel alloys, Thermal stresses, Strains & stresses (Mechanics), Mechanical loads
Abstract: In service, aero-engine turbine blades are frequently subjected to transient thermal and mechanical excursions superimposed on long-term creep loading; however, the associated microstructural degradation mechanisms remain insufficiently understood. This study investigates the influence of short-term overloading or overheating on the creep behavior and microstructural evolution of the nickel-based single crystal superalloy DD6. Creep tests were conducted at 1050 °C and 150 MPa, with overloading (200 MPa for 20 h) or overheating (1150 °C for 0.5 h) applied during the secondary creep stage. Overloading markedly accelerated creep strain accumulation, fragmented the γ matrix into discrete segments, increased γ/γ' interfacial incoherency, and promoted the formation of dense interfacial dislocation networks. The elevated strain energy further enhanced γ' shearing during tertiary creep, facilitating the nucleation of subgrain boundaries within the γ' phase. Short-term overheating similarly increased the creep rate but additionally induced partial γ' dissolution, reducing its volume fraction and widening γ channels. The transient thermal spike enhanced dislocation mobility and annihilation, temporarily lowering the dislocation density. However, the weakened γ' precipitates exhibited diminished resistance to dislocation cutting at later creep stages, leading to severe dislocation entanglement, extensive subgrain boundary formation, and the development of high-density dislocation networks within the γ' phase. Collectively, these results elucidate the distinct damage pathways associated with transient overloading and overheating and provide a microstructural basis for more accurate life assessment and optimized design of nickel-based single-crystal turbine blade superalloys. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:In service, aero-engine turbine blades are frequently subjected to transient thermal and mechanical excursions superimposed on long-term creep loading; however, the associated microstructural degradation mechanisms remain insufficiently understood. This study investigates the influence of short-term overloading or overheating on the creep behavior and microstructural evolution of the nickel-based single crystal superalloy DD6. Creep tests were conducted at 1050 °C and 150 MPa, with overloading (200 MPa for 20 h) or overheating (1150 °C for 0.5 h) applied during the secondary creep stage. Overloading markedly accelerated creep strain accumulation, fragmented the γ matrix into discrete segments, increased γ/γ' interfacial incoherency, and promoted the formation of dense interfacial dislocation networks. The elevated strain energy further enhanced γ' shearing during tertiary creep, facilitating the nucleation of subgrain boundaries within the γ' phase. Short-term overheating similarly increased the creep rate but additionally induced partial γ' dissolution, reducing its volume fraction and widening γ channels. The transient thermal spike enhanced dislocation mobility and annihilation, temporarily lowering the dislocation density. However, the weakened γ' precipitates exhibited diminished resistance to dislocation cutting at later creep stages, leading to severe dislocation entanglement, extensive subgrain boundary formation, and the development of high-density dislocation networks within the γ' phase. Collectively, these results elucidate the distinct damage pathways associated with transient overloading and overheating and provide a microstructural basis for more accurate life assessment and optimized design of nickel-based single-crystal turbine blade superalloys. [ABSTRACT FROM AUTHOR]
ISSN:00222461
DOI:10.1007/s10853-026-13129-5