In-Situ Analysis of Subsurface Microstructural Performance after Peening

Peening operations are common to many applications and are continually diversifying. Each method has unique advantages and limitations, but one disadvantage common among traditional, impact-mediated peening operations is the stochastic nature of impacts in terms of energy, trajectory, and position. Because of this randomness, these processes can only be controlled by setting global parameters, such as total surface coverage, air pressure, stand-off distance, shot size and geometry, etc. Although practical in application, it limits the fundamental understanding and optimization of these techniques on a per-impact basis. The work presented here highlights a new patterned peening process where the exact energy and location of impacts can be dictated to tailor the surface properties. This technique has shown significant strength and fatigue life increases in processed parts, and this presentation examines the sub-surface microstructure by EBSD and in-situ tensile testing. This allows the interior and surface regions to be examined independently under stress in order to highlight mechanistic aspects that can be related to all peening operations.