Experimental investigation and life prediction of hot corrosion pre-exposure on low-cycle fatigue of a directionally solidified nickel-base superalloy

摘要

Low-cycle fatigue tests were conducted on the directionally solidified nickel-base super-alloy DZ125 at 850℃ in the unexposed and exposed specimens for 2, 15, 25 and 50h in hot corrosion environment. The pre-exposed specimen exhibited a lower life than unexposed specimens. Fatigue cracks in the unexposed specimens are initiated from defects near the surface, while the cracks of exposed specimens preferentially occur on the surface. Hot corrosion damage in fatigue life was found to be associated with the reduction of the bearing area. A novel life prediction methodology based on continuum damage mechanics was proposed to predict the experimentally observed decrease in low-cycle fatigue life with increasing prior exposure time.