Cyclic Behavior of Turbine Disk Alloys at 650°C

Five gas turbine disk alloys representing a range of strengths and processing methods were tested for resistance to both cyclic crack initiation and propagation at 650° C using a 0.33 Hz fatigue cycle and a cycle incorporating a 900 s tensile dwell. At the low strain ranges pertinent to disks, resistance to crack initiation increased with increasing tensile yield strength among the alloys, though the advantage was somewhat smaller for the creep fatigue cycle. Cyclic crack growth resistance, however, decreased with increasing strength and very markedly so for the dwell cycle.