Metallurgical evaluation of a commercial engine gas turbine HPT midseal involved in an uncontained event and associated determination of root cause

The metallurgical evaluation covers the examination of a high pressure turbine midseal that was involved in an uncontained event that included identifying the origin area and growth mode. The investigation then expanded to look at additional fielded parts for commonality/differences. A second fielded part was found cracked and a hypothesis was generated based their mission profiles and seeing how they differed from the larger population of parts. Eventually a viable hypothesis was proposed and a factory test was constructed/instrumented, which was verified the distress mode and helped determine appropriate field action.