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Effect of Squareness of Initial γ′ Precipitates on Creep-Rupture Life of a Ni-Base Single Crystal Superalloy at 760/982°C

Effect of Squareness of Initial γ′ Precipitates on Creep-Rupture Life of a Ni-Base Single Crystal... An approach to determination of squareness of initial γ′ precipitates (S 2D) is proposed to evaluate its effect on creep-rupture life (t r) of nickel-base single crystal (SC) superalloys. It is found that the 760/982 °C rupture life varied with the change in regional S 2D caused by redistribution of W when 1st-step aging temperature changed in full heat treatment on superalloy DD83 investigated. The longest creep-rupture life occurred at the highest value/the lowest difference in S 2D in the interdendritic regions/between the typical dendritic regions in DD83. It is also found that S 2D is a weighted function of the area fraction (F 2D), spacing (h), and size (d) of γ′ precipitates and is closely related to t r in a series of SC superalloys. In addition, the variation of S 2D with F 2D (here, thermodynamic mole fraction is approximately expressed by F 2D) through lattice misfit (δ) in the SC superalloys with F 2D ranging from ~ 60 to 75 pct is well correlated. Therefore, to reveal and to better understand these relationships and correlations may help to optimize the phase variables in order to achieve a long rupture life of SC superalloys. In addition, functions to reveal the interrelationships of F 2D, volume fraction (F 3D), S 2D, and cuboidness (S 3D) of initial γ′ precipitates are derived considering their shape changes. All of these are hoped to be helpful in practical applications and in understanding the true meaning of the related variables. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Metallurgical and Materials Transactions A Springer Journals

Effect of Squareness of Initial γ′ Precipitates on Creep-Rupture Life of a Ni-Base Single Crystal Superalloy at 760/982°C

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Publisher
Springer Journals
Copyright
Copyright © 2018 by The Minerals, Metals & Materials Society and ASM International
Subject
Materials Science; Metallic Materials; Characterization and Evaluation of Materials; Structural Materials; Surfaces and Interfaces, Thin Films; Nanotechnology
ISSN
1073-5623
eISSN
1543-1940
DOI
10.1007/s11661-018-4635-y
Publisher site
See Article on Publisher Site

Abstract

An approach to determination of squareness of initial γ′ precipitates (S 2D) is proposed to evaluate its effect on creep-rupture life (t r) of nickel-base single crystal (SC) superalloys. It is found that the 760/982 °C rupture life varied with the change in regional S 2D caused by redistribution of W when 1st-step aging temperature changed in full heat treatment on superalloy DD83 investigated. The longest creep-rupture life occurred at the highest value/the lowest difference in S 2D in the interdendritic regions/between the typical dendritic regions in DD83. It is also found that S 2D is a weighted function of the area fraction (F 2D), spacing (h), and size (d) of γ′ precipitates and is closely related to t r in a series of SC superalloys. In addition, the variation of S 2D with F 2D (here, thermodynamic mole fraction is approximately expressed by F 2D) through lattice misfit (δ) in the SC superalloys with F 2D ranging from ~ 60 to 75 pct is well correlated. Therefore, to reveal and to better understand these relationships and correlations may help to optimize the phase variables in order to achieve a long rupture life of SC superalloys. In addition, functions to reveal the interrelationships of F 2D, volume fraction (F 3D), S 2D, and cuboidness (S 3D) of initial γ′ precipitates are derived considering their shape changes. All of these are hoped to be helpful in practical applications and in understanding the true meaning of the related variables.

Journal

Metallurgical and Materials Transactions ASpringer Journals

Published: May 11, 2018

References