The effects of inhomogeneous microstructure and loading waveform on creep-fatigue behaviour in a forged and precipitation hardened nickel-based superalloy

The aim of the present paper is to identify the effects of sampling locations and loading waveforms on high-temperature low-cycle fatigue (HTLCF) and creep-fatigue life of a forged and precipitation hardened nickel-based GH4169 superalloy. Both the deformation and failure mechanisms are considered here. It has been revealed that HTLCF and creep-fatigue life of specimens were influenced by inhomogeneous microstructures at different locations. Compared with the HTLCF tests, the presence of dwell times in creep-fatigue tests tended to reduce number of cycles to failure. Intergranular damage was observed at both crack initiation and propagation stages. For the dwell times under tension, the intergranular damage was mainly associated with precipitate-assist voids. However, oxidation accounted for the presence of intergranular damage for the dwell times under compression.