The low cycle fatigue property, damage mechanism, and life prediction of additively manufactured Inconel 625: Influence of temperature

Symmetrical high‐temperature low‐cycle fatigue tests were performed in this study to examine the influence of temperature on the fatigue failure mechanism of the additively manufactured Inconel 625. According to the fracture analysis, cracks initiate from the crystallographic plane at room temperature. At 600°C, oxidation of carbides leads to crack initiation. The strengthening effect of γ ″ precipitation prevents crack propagating within the matrix. At 750°C, the crack becomes transgranular propagating, as a consequence of γ ″‐ δ transformation. Geometrically necessary dislocations distribution on the fracture supports this result. Furthermore, a modified life prediction formula considering effect of temperature and strain amplitude was established. It was observed that the modified model predicted the fatigue life of the studied materials well in both test conditions. Cracks initiate from favorable slip plane at room temperature. Precipitation of γ ″ at 650°C prevents dislocation shearing into the matrix. Cyclic plastic deformation accelerates the γ ″‐ δ transformation at 700°C. Life prediction model considering strain amplitude and temperature shows good accuracy.