VHCF life of AM1 Ni-based single crystal superalloy after pre-deformation

VHCF properties of the Ni-based single crystal superalloy AM1 with pre-deformation have been investigated at 1000 ?C. Pre-deformed material did not present life debit under fully reversed conditions (R = -1). Predeformation decreased VHCF lifetime under high mean stress conditions (R = 0.5) with a shift from internal to mode I surface crack initiation. The pre-deformed material has microstructure coarsened bands lying on the former {111} slip planes, facilitating microstructure shearing during VHCF at R = 0.5. Slip traces increased surface roughness, causing a surface recrystallization and initiation of the fatal crack from the surface. Rejuvenation heat treatment after pre-deformation can restore the microstructure and the fatigue life.

Automated summary

The VHCF properties of the Ni-based single crystal superalloy AM1 with pre-deformation at 1000°C were studied. Pre-deformation did not result in life reduction under fully reversed conditions (R = -1), but decreased VHCF lifetime under high mean stress conditions (R = 0.5) with a shift in crack initiation from internal to surface. The pre-deformed material exhibited coarsened microstructure bands on slip planes, leading to surface roughness and initiation of fatal cracks. Rejuvenation heat treatment post pre-deformation could restore microstructure and fatigue life.