Evaluation of Residual Strains Produced by Laser Shock Processing for Low Pressure Steam Turbine Blade Applications using Bragg Edge Neutron

The use of steam turbines is the primary method of power extraction for most power plants. The corrosion resistant steel blades bear significant centrifugal loads in a wet steam environment making them susceptible to stress corrosion cracking and fatigue. A surface technique known as Laser Shock Peening (LSP) can be used to generate beneficial Compressive Residual Stresses (CRS) at the highly stressed blade root in order to resist crack initiation. Achieving a consistent stress field around a complex component such as a low pressure steam turbine blade, therefore requires significant insight into the geometric effects on LSP processing. Conventional residual stress measurements can be hindered by the geometry and are specific to that location. The full field strain neutron imaging at IMAT offers the ideal technique to reveal the effectiveness of the LSP process around complex geometries.