EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

The main aim if this study is to investigate influence of coarse grained microstructure of a nickel-based superalloy on TMF crack growth behaviour. For this purpose, single-edge U-shaped notched (SEN) and corner crack (CC) specimens were machined and tested under out-of-phase (OP) and in-phase (IP) TMF crack growth test conditions between 400 and 750 oC in laboratory air. The loading waveform was triangular with a load ratio of R=0 and no hold time. All tests were run on servo-hydraulic test machines with induction heating systems. The crack length was measured using the compliance method with the SEN specimens and a direct current potential drop (DCPD) technique on the CC specimens. Electron backscatter diffraction (EBSD) was used in order to relate the crack growth path to the microstructure on the micron scale. The EBSD characterisation was made by orientation mapping of metallographically prepared specimens in an advanced HITACHI SU-70 field emission gun scanning electron microscope (FEG-SEM) equipped with the Oxford Instruments ESBD detector. Micro-hardness was also measured to examine crack closure effects on the deformed material around the crack tip. It has been found, that in the coarse grained material TMF in-phase crack growth rates are highly sensitive to the material microstructure. TMF out-of-phase tests show no sensitivity to microstructural aspects.

This study has received funding from the Clean Sky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 686600.