Retained residual stress profiles in a laser shock-peened and shot-peened nickel base superalloy subject to thermal exposure

Purpose - The purpose of this paper is to analyze the residual stress relaxation in laser shock-peened and shot-peened IN100 subject to thermal exposure. Design/methodology/approach - Shot peening (SP) is a commonly used surface treatment that imparts compressive residual stress into the surface of components. The shallow depth of compressive residual stresses, and the extensive plastic deformation associated with SP, has been overcome by modern approaches such as laser shock peening (LSP). LSP surface treatment produces compressive residual stress magnitudes that are similar to SP that extend four to five times deeper, and with less plastic deformation. Retention of compressive surface residual stresses is necessary to retard initiation and growth of fatigue cracks under elevated temperature loading conditions. Findings - Results indicated that the LSP processing retains a higher percentage of the initial residual stress profile over that of SP. Originality/value - The retained residual stresses after thermal exposure of these surface treatment processes can be incorporated into a life prediction methodology that takes credit for beneficial compressive surface residual stresses to delay initiation and retard fatigue crack growth.