Metallurgical evaluation of multiple events associated with fracture/liberation of LPT stage 3 disks from legacy commercial gas turbines

A series of events resulted from fracture of LPT stage 3 disk spacer arms after 15 years with no reported shop finds/events. The investigation covers the metallurgical examination of the fractures, determination of mode, and covers the causes for fracture/operational changes and other factors related to determining root cause.