Life Extension of Life Limited Jet Engine Components Using a Large Chamber Scanning Electron Microscope

Tinker AFB is a sustainment base that performs maintenance and overhaul of various military aircraft and jet engines.  With multiple Program Offices and Depot product lines to support, the Metallurgical Analysis Section performs failure analyses, mishap investigations, material consultations, product characterization, and first article testing.  With state-of-the-art and globally novel equipment and capabilities, this laboratory continues to add value to the Air Force.  Depot maintenance challenges are numerous, especially when considering supply chain demands and parts availability.  One specific area facing continuous availability challenges is life limited turbine engine parts.  One lab-unique capability that has facilitated the inspection of large turbine parts is the world’s largest scanning electron microscope.  With the aid of this instrument, as-cleaned parts are inspected without having to condemn for high magnification inspection.  This creates the opportunity to accomplish large part non-destructive health assessments for continued service viability and/or life extension considerations.    Many rotating parts have service lives that have been established via modelling, historical performance data, and test data on fatigue crack growth rates.  Often times, these operational lives must be decremented based upon a number of considerations. The Metallurgical Analysis Section at Tinker AFB, in cooperation with the Air Force Materiel Command (AFMC) propulsion group and the Air Force Research Labs (AFRL) at WPAFB, has been evaluating specific parts identified as candidates for life extension, that is, the attainment of the full safe component life.  To date, three components from the F100 engine have been re-inspected via traditional non-destructive methods, visual inspection, and large chamber SEM analyses.  Two have been approved for life extension and will be returned to service, saving taxpayers and the government millions of dollars both now and into the future.  This is an up to date summary of this life extension effort.