In Situ Observation of Small Crack Growth and Fatigue Life Modeling for In713C Ni‐Based Superalloy

ABSTRACT Fatigue failure has a considerable impact on the safety of equipment in service. The fatigue crack growth behavior of a Ni‐based superalloy was investigated by in situ fatigue testing. The results showed that microstructurally small crack growth speed followed a “V‐shaped” pattern. Notch effect activated multiple slip systems, and small cracks within grains tended to grow along slip bands parallel with {111} planes. Moreover, due to obstructive effects of cross‐slip, grain boundaries, and carbides, the growth path was deflected. During this process, plastic deformation at the crack tip caused grains to rotate, with angular changes ranging from 6° to 10°. Finally, based on the fatigue crack growth mechanism, models for microstructurally small and long crack growth rates to predict the high‐cycle/very‐high‐cycle fatigue life were established. The predicted results were within factors of three for surface failure and two for interior failure.