Evaluation of fatigue crack growth rate and life prediction of Inconel 718at room and elevated temperatures

The fatigue crack growth behavior of Inconel 718 was investigated under rot ating bending fatigue at room temperature, 300, 500, and 600 degrees C in a ir. It has been found that the small crack growth rate could be evaluated b y the small crack growth law at high stress levels, where the small-scale y ielding conditions are exceeded and the Paris law is not applicable, irresp ective of the temperature. The fatigue strength of plain specimens increase d considerably in the long-life region at the elevated temperatures, becaus e the early growth of a small crack in the range of 20-30 mu m was suppress ed. However, a crack grew faster at higher temperature after growing beyond about 50 mu m due to the decrease of crack growth resistance. The fatigue life in the stable crack growth period can be predicted by the small crack growth law. (C) 2000 Elsevier Science S.A. All rights reserved.