A. Sengupta et al., FATIGUE-CRACK GROWTH-BEHAVIOR OF A NEW SINGLE-CRYSTAL NICKEL-BASED SUPERALLOY (CMSX-4) AT 650-DEGREES-C, Journal of materials engineering and performance, 3(4), 1994, pp. 540-550
The fatigue crack growth behavior of a new single crystal nickel-based
superalloy containing rhenium (CMSX-4) has been studied at 650 degree
s C. The investigation also examined the influence of gamma' precipita
tes (size and distribution) on the near-threshold fatigue crack growth
rate and the fatigue threshold. The influence of load ratio on the fa
tigue crack growth rate and the fatigue threshold was also examined. D
etailed fractographic studies were carried out to determine the crack
growth mechanism in fatigue in the threshold region. Compact tension s
pecimens were prepared from the single crystal nickel-based superalloy
CMSX-4 with [001] orientation as the tensile loading axis direction.
These specimens were given three different heat treatments to produce
three different gamma' precipitate sizes and distributions. Fatigue cr
ack growth behavior of these specimens was studied at 650 degrees C in
air. The results of the present investigation indicate that the near-
threshold fatigue crack growth rate decreases and that the fatigue thr
eshold increases with an increase in the gamma' precipitate size at 65
0 degrees C. The fatigue threshold decreased linearly with an increase
in load ratio. Fractographs at 650 degrees C show a stage II type of
crack growth along {100} type of crystal planes in the threshold regio
n, and along {111} type of crystal planes in the high Delta K region.