Multispot laser peening using phase modulated laser beam

Multispot laser peening was conducted on austenitic stainless steel (SUS316L) using a Nd:YAG laser as the laser source to generate a high-intensity pulse ranging from 0.5–4 GW/cm². A liquid-crystal-on-silicon spatial light modulator (LCOS-SLM) was used for laser division to create multiple spots on the target. Multiple laser pulses irradiating a metal surface simultaneously induce multiple shock waves. This approach leads to a thicker plastically deformed layer compared with laser-induced shock waves produced by a single pulse. The laser peening performance was evaluated by measuring the magnitude of the compressive residual stress, hardness difference, and magnitude of the laser-induced shock wave. The laser intensity and laser irradiation patterns were adapted as the laser peening parameters throughout the experiment.