J. Byrne et al., ELEVATED-TEMPERATURE FATIGUE-CRACK GROWTH UNDER DWELL CONDITIONS IN WASPALOY, International journal of fatigue, 19(5), 1997, pp. 359-367
Growth of corner cracks at temperatures up to 700 degrees C under cycl
ic (0.25 Hz), 300 s dwell at peak load, both at R = 0.1, and constant
load conditions has been studied in the nickel base turbine disc alloy
Waspaloy. No significant effect of dwell on fatigue crack growth rate
(da/dN) is found at 550 degrees C, where transgranular fatigue cracki
ng predominated. At 600 and 650 degrees C, under dwell cycling a trans
ition to entirely intergranular cracking is accompanied by a severe in
crease in cyclic crack growth rate. Contrary to the trend for 600-650
degrees C, dwell and constant load data at 700 degrees C shows lower c
rack growth rates than for 650 degrees C, indicating that a time depen
dent microstructural change occurs during prolonged exposure at 700 de
grees C generating an increased resistance to intergranular cracking.
Using the stress intensity range (Delta K) as a correlating parameter,
fatigue crack growth rates are successfully predicted by linear summa
tion of pure fatigue and time dependent data. (C) 1997 Elsevier Scienc
e Ltd.