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Poor machining practice = Reduced Fatigue life = Early Component Failure
Selected incidents related to hole manufacture:
Early 90's: Cracks discovered in 9 Inco 718 and Rene 95 discs
7/96: Pratt & Whitney's Titanium disks fail during take-off
1999 Forward Outer Seal crack discovered at a drilled/reamed bolt hole in Inco 718
- No visual or FPI indications at manufacture (1986, pre-P11TF12)
- Machining Parameters meet current P11TF12
- Metallography indicates severe overheat
- Lab simulation indicates likely loss of coolant during drilling.
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