Technical Briefs

Creep Degradation of Thermally Exposed IN738C Superalloy

[+] Author and Article Information
M. Aghaie-Khafri1

Faculty of Mechanical Engineering, K.N. Toosi University of Technology, P.O. Box 19395-1999, Tehran, 1999143344, Iranmaghaei@kntu.ac.ir

S. Farahany

Faculty of Mechanical Engineering, K.N. Toosi University of Technology, P.O. Box 19395-1999, Tehran, 1999143344, Iran


Corresponding author.

J. Eng. Gas Turbines Power 131(3), 034501 (Jan 29, 2009) (3 pages) doi:10.1115/1.3019056 History: Received October 31, 2007; Revised September 20, 2008; Published January 29, 2009

Creep degradation of an IN738C superalloy after long-term thermal exposure in an atmospheric furnace was investigated by means of accelerated creep tests. Experimental observation showed that the minimum creep rate increased by increasing the exposure time or exposure temperature and is a key factor for predicting creep life during long time, high temperature service. Concerning the exposure temperature and time, an empirical equation has been presented to estimate the creep lives of the pre-exposed specimens. Furthermore, the accuracy of the Monkman–Grant (Proceedings of ASTM, Vol. 56, pp. 593–620) relationship has been verified by experimental results.

Copyright © 2009 by American Society of Mechanical Engineers
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Figure 4

Graphical representation of the Monkman–Grant equation for IN738C

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Figure 5

Time to tertiary creep versus minimum creep rate in IN738C

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Figure 3

A plot of Eq. 1 where contour numbers represent minimum creep rates (1/h) at different pre-exposure temperatures and times

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Figure 2

Variation of (a) stress rupture life and (b) minimum creep rate of IN738C samples with exposure time at different exposure temperatures

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Figure 1

Typical creep curve of the IN738C sample after aging for 100 h at 800°C

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Figure 6

A plot of log (strain rate) versus (tp+ts)/(εp+εs) for exposed IN738C samples



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