Laser shock processing on Ni-based superalloy K417 and its effect on thermal relaxation of residual stress

Abstract

The compressive residual stress fields at ambient temperature and stress relaxation at elevated temperatures of nickel-based alloy K417 by laser shock processing (LSP) were investigated by the finite element analysis and experimental method. A temperature and strain rate-dependent plasticity model of Johnson–Cook (JC) material model was utilized to investigate the residual stress evolution under LSP and thermal loads. The residual stress distributions of original and processed specimens were measured by the X-ray diffraction method. Zener–Wert–Avrami function was employed to study the thermal relaxation process of LSP K417, and the simulated results have a significant agreement with the experimental data. Specifically, most of stress relaxation occurs before 30 min of exposure, and the relaxation amplitude increases with the rise of applied temperature. The activation enthalpy of the relaxation process for LSP K417 obtained from simulation and experiment are determined to be 2.86 and 2.85 eV respectively.