Effects of temperature and hold time on creep-fatigue crack-growth behavior of HAYNES® 230® alloy

The creep-fatigue crack-growth behavior of a HAYNES 230 superalloy was investigated at the temperatures of 649, 816 and 927 °C in laboratory air. The crack-growth experiments were conducted under the stress-intensity-factor-range or load-range control. Hold times in the range of 3 s to 5 h were imposed at the maximum load to study the influence of hold time on the crack-growth behavior. The fatigue and creep crack-propagation experiments were also performed as zero and infinite hold-time experiments, respectively.The crack-growth rate increased continuously with increasing the test temperature and/or hold time. The fracture surfaces and cross-sections through the fracture surfaces were examined. As the hold time increased, the fracture appearance changed from the transgranular to intergranular mode. At higher temperatures, this transgranular–intergranular transition occurred at a shorter hold time.