Non-Destructive Inspection (NDI) for recrystallized grains in single crystal superalloys

Recently, the F-35 program experienced fatigue cracking in a low pressure turbine blade inside the F135 engine from recrystallization (RX). These problems cost the program time and money, strain the political capital necessary to sustain a large weapons program, and undermine the confidence of domestic and international partners. In response, TRI/Austin proposes utilizing an ultrasonic acoustic birefringence NDI technique to ensure turbine blade quality control. Instances of RX will be identified in single crystal superalloys through the changes in density as interpreted by transducers as the ultrasonic waves are sent through the part. To validate this approach, TRI/Austin will team with the Advanced Manufacturing Center (AMC) at the University of Texas at Austin. AMC will fabricate a set of NDI specimens with controlled incidents of RX introduced via deforming the specimens to introduce plastic strain before relieving in a vacuum furnace. The goal of these activities is a design for an inspection system at Pratt & Whitney to provide immediate go/no-go for the turbine blades as they are received from the casting house in Phase II, validated by testing against a set of specimens with controlled RX.