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Research Papers

Low Cycle Fatigue of Alloy 617 at 850 °C and 950 °C

[+] Author and Article Information
J. K. Wright

e-mail: Jill.Wright@inl.gov

R. N. Wright

Materials Science and Engineering,
Idaho National Laboratory,
P. O. Box 1625,
Idaho Falls ID 83415

Contributed by Materials Division of ASME for publication in the Journal of Engineering Materials and Technology. Manuscript received March 21, 2012; final manuscript received January 3, 2013; published online May 6, 2013. Assoc. Editor: Marwan K. Khraisheh.

J. Eng. Mater. Technol 135(3), 031005 (May 06, 2013) (8 pages) Paper No: MATS-12-1052; doi: 10.1115/1.4023673 History: Received March 21, 2012; Accepted January 03, 2013

The low cycle fatigue behavior of Alloy 617 has been evaluated at 850 °C and 950 °C, the temperature range of particular interest for the intermediate heat exchanger on a proposed high-temperature gas-cooled nuclear reactor. Cycles to failure were measured as a function of total strain range and varying strain rate. Results of the current experiments compare well with previous work reported in the literature for a similar range of temperatures and strain rate. The combined data demonstrate a Coffin–Manson relationship, although the slope of the Coffin–Manson fit is close to −1 rather than the typically reported value of −0.5. At 850 °C and a strain rate of 10−3 /s Alloy 617 deforms by a plastic flow mechanism in low cycle fatigue and exhibits some cyclic hardening. At 950 °C for strain rates of 10−3–10−5 /s, Alloy 617 deforms by a solute drag creep mechanism during low cycle fatigue and does not show significant cyclic hardening or softening. At this temperature the strain rate has little influence on the cycles to failure for the strain ranges tested.

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References

Figures

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Fig. 1

Illustration of failure criterion

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Fig. 2

Example of transgranular fracture path shown in specimen tested at 0.3% total strain and 950 °C

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Fig. 3

Hysteresis loops from midlife cycle for three replicate samples (shown in different colors) tested at 950 °C and 10−3 /s for (a) 0.4% and (b) 1.0% total strain

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Fig. 4

Maximum and minimum stresses shown for three replicate samples tested at 950 °C and 10−3 /s for (a) 0.4% and (b) 1.0% total strain

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Fig. 5

Peak tensile and compressive stress plotted as a function of cycle for one fatigue test specimen at each total strain range for (a) 850 °C and (b) 950 °C

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Fig. 6

The maximum tensile stress at the midcycle plotted as a function of total strain range for 850 °C and 950 °C

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Fig. 7

Stress-strain hysteresis plots for the fatigue tests are shown for selected cycles for 0.6% total strain range at (a) 850 °C and (b) 950 °C

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Fig. 8

The hysteresis loops for a midcycle at each total strain range for (a) 850 °C and (b) 950 °C

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Fig. 9

The effect of strain rate on (a) fatigue life and (b) maximum tensile stress at 950 °C

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Fig. 10

Fatigue data for (a) 850 °C and (b) 950 °C plotted with data compiled by Yukawa [11] at strain rates of 4 × 10−3 /s and temperatures from 815 °C to 1000 °C. Alloy 617 data from the work of Totemeier and Tian [15] at 1000 °C are also plotted.

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Fig. 11

Effect of test temperature on fatigue life at a strain rate of 10−3 /s

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Fig. 12

Coffin–Manson plot for LCF tests at 10−3 /s, showing a slope of approximately −1.0 when inelastic strain is plotted as a function of fatigue life

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Fig. 13

Tensile portion of first cycle of the 2% total strain range fatigue hysteresis loop shown with maximum tensile stress values of the 10th and midcycle for each total strain range tested at (a) 850 °C and (b) 950 °C

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Fig. 14

Cyclic hardening at 850 °C determined by fitting Eq. (2) to stress amplitude versus inelastic strain

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Fig. 15

First cycle of 950 °C fatigue tests at three different strain rates

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Fig. 16

Exponential fits to the stress transient observed in the first fatigue cycle at 950 °C for strain rates of (a) 10−3 /s, (b) 10−4 /s, and (c) 10−5 /s

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Fig. 17

First, second, and tenth cycle of a 2% total strain range fatigue test at 950 °C

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