Overgrown grains appearing during sub-solvus heat treatment in a polycrystalline γ-γ’ Nickel-based superalloy

Charpagne, Marie-Agathe; Franchet, Jean‐Michel; Bozzolo, Nathalie

doi:10.1016/j.matdes.2018.02.048

Cited by 49 publications

(14 citation statements)

References 35 publications

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“…It is conducive to DRX nucleation [ 45 ]. In addition, previous reports show that less time for deformation and γ′ phase pinning results in a low X drx and fine grains at a high strain rate [ 46 ]. The grains with high GOS have hardly been observed at 1140 °C and the X drx at three strain rates are higher than 95%, which indicates the DRX is complete.…”

Section: Resultsmentioning

confidence: 99%

Modeling Dynamic Recrystallization Behavior in a Novel HIPed P/M Superalloy during High-Temperature Deformation

et al. 2022

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The dynamic recrystallization (DRX) features and the evolution of the microstructure of a new hot isostatic pressed (HIPed) powder metallurgy (P/M) superalloy are investigated by hot-compression tests. The sensitivity of grain dimension and DRX behavior to deformation parameters is analyzed. The results reveal that the DRX features and grain-growth behavior are significantly affected by deformation conditions. The DRX process is promoted with a raised temperature/true strain or a reduced strain rate. However, the grains grow up rapidly at relatively high temperatures. At strain rates of o.1 s−1 and 1 s−1, a uniform microstructure and small grains are obtained. Due to the obvious differences in the DRX rate at various temperatures, the piecewise DRX kinetics equations are proposed to predict the DRX behavior. At the same time, a mathematical model for predicting the grain dimension and the grain growth behavior is established. To further analyze the DRX behavior and the changes in grain dimension, the hot deformation process is simulated. The developed grain-growth equation as well as the piecewise DRX kinetics equations are integrated into DEFORM software. The simulated DRX features are consistent with the test results, indicating that the proposed DRX kinetics equations and the established grain-growth model can be well used for describing the microstructure evolution. So, they are very useful for the practical hot forming of P/M superalloy parts.

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Section: Resultsmentioning

confidence: 99%

Modeling Dynamic Recrystallization Behavior in a Novel HIPed P/M Superalloy during High-Temperature Deformation

et al. 2022

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“…To prevent the occurrence of ALGs, many ad hoc studies [3,[18][19][20][21][22][23][24][25][26][27][28][29] have been conducted to find the critical window of strain and/or strain rate. For example, it has been found that nominal compressive strain below 10% could trigger the occurrence of ALGs after supersolvus heat treatment [19].…”

Section: Introductionmentioning

confidence: 99%

Formation mechanism of abnormally large grains in a polycrystalline nickel-based superalloy during heat treatment processing

et al. 2019

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Controlling the final grain size in a uniform and controlled manner in powder metallurgy nickel-based superalloys is important since many mechanical properties are closely related to it. However, it has been widely documented that powder metallurgy superalloys are prone to suffer from growth of abnormally large grains (ALGs) during supersolvus heat treatment, which is harmful to in-service mechanical performance. The underlying mechanisms behind the formation of ALGs are not yet fully understood. In this research, ALGs were intentionally created using spherical indentation applied to a polycrystalline nickel-based superalloy at room temperature, establishing a deformation gradient underneath the indentation impression, which was quantitatively determined using finite element modelling, electron backscatter diffraction (EBSD) and synchrotron diffraction. Subsequent supersolvus heat treatment leads to the formation of ALGs in a narrow strain range, which also coincides with the contour of residual plastic strain in a range of about 2% to 10%. The formation mechanisms can be attributed to: (1) nucleation sites available for recrystallization are limited, (2) gradient distribution of stored energy across grain boundary. The proposed mechanisms were validated by the phase-field simulation. This research provides a deeper insight in understanding the formation of ALGs in polycrystalline nickel-based superalloy components during heat treatment, when subsurface plastic deformation caused by (mis)handling before super-solvus heat treatment occurs. The practical relevance of looking at small strains at room temperature this research is to understand what happens when turbine disks undergo small dents and scratches during (mis) handling before heat treatment.

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“…Cobalt-based superalloys may develop some precipitation strengthening from carbides (Cr 7 C3, M 23 C 6 ). No intermetallic phase is strengthening equal to γ strengthening in nickel-base alloys [72,73].…”

Section: Discussionmentioning

confidence: 99%

Frequency Analysis of Transients in Electrochemical Noise of Superalloys Waspaloy and Ultimet

Jáquez-Muñoz

Gaona‐Tiburcio

Miramontes

et al. 2021

Metals

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Nickel or Cobalt-based superalloys represent an important class of engineering materials, finding widespread application in critical components within the gas turbine engines used for jet propulsion and electricity generation. This research aimed at the frequency analysis of transients in electrochemical noise of Waspaloy and Ultimet superalloys, immersed in 3.5 wt.% in H2SO4 and NaCl solutions at two different temperatures, 25 and 60 °C. Localized corrosion behavior of superalloys was assessed using the electrochemical noise technique (EN) according to ASTM-G199 standard. Three different statistical methods filtered the EN signal, and the polynomial method was employed to obtain the noise resistance (Rn), the localization index (LI), skew and kurtosis, and the power spectral density analysis (PSD). Results indicate that the current and potential noise transients have a better behavior with better clarity when a polynomial is used to show a localized corrosion kurtosis for both superalloys.

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Overgrown grains appearing during sub-solvus heat treatment in a polycrystalline γ-γ’ Nickel-based superalloy

Cited by 49 publications

References 35 publications

Modeling Dynamic Recrystallization Behavior in a Novel HIPed P/M Superalloy during High-Temperature Deformation

Modeling Dynamic Recrystallization Behavior in a Novel HIPed P/M Superalloy during High-Temperature Deformation

Formation mechanism of abnormally large grains in a polycrystalline nickel-based superalloy during heat treatment processing

Frequency Analysis of Transients in Electrochemical Noise of Superalloys Waspaloy and Ultimet

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