Non-Destructive Residual Stress Measurement in Nickel Superalloy Turbine Blades by XRD

To achieve full turbine blade life in a modern gas turbine engine, it is critically important to measure and manage the state of residual stresses in high stress areas of the blade. Unfortunately there is no affordable, nondestructive technique commercially available to measure residual stresses in complex geometries like the under side platform areas of gas turbine blades. This proposed project will demonstrate a methodology and equipment for nondestruvtive residual stress measurement in critical locations of single crystal and directionally solified superalloy turbine blade roots with complex geometries. The project will also seek to demonstrate the use of spatial statistical engineering techniques to analyze three dimensional residual stress data obtained using unique x-ray diffraction techniques. Several blades will be destructively analyzed to establish three dimensioinal residual stress plots in a typical critical high stress location of DS and single crystal turbine blades. Subsequently, a relatively small number of blades will be nondestructively inspected for compressive residual stress at a common high stress location and the data analyzed using spatial statistical techniques. It is anticipated an affordable residual stress measurement technique will be demonstrated as well as statistical methods for analyzing the data for use as a tool to establish minimum residual stress levels and distrubution in critical areas of directionally solified and single crystal turbine blades.