segregation-induced-turbine-disk-failureFailed disk: top layer in thebillet headDisk from theparallel engine: coincidentally, directly below the failed disk in the billetNext disk in thebillet: was not yetinstalledAs the distance to the billet head increases, flawsize and frequency decrease, and the position of theflaws moves towards the disk hub bore. Annulus section that brokeout due to a large carbonnitride segregationca. 1 mDuring an acceptance run on the ground, the first stage rotor disk failed and released uncontained fragments.Fracture of a turbine disk due to a segregation in theannulus that was several centimeters across.