Laser peening in a high-vacuum environment

Laser peening is a surface-enhancement technique that uses a high intensity of several gigawatts for the cold working of metal samples. The most notable feature of this technique is its effective treatment of the depths of metal samples. A transparent coating, known as a plasma confinement layer, is typically used in laser peening to suppress the expansion of the plasma away from the metal surface. The ability to confine the plasma significantly affects the effectiveness of laser peening. Water is commonly used as a plasma confinement layer due to its transparency, cost-effectiveness, ease of handling, and its ability to conform to the shape of metal as a liquid. However, in high-vacuum environments, only solid-state media can be used as plasma confinement layers. In this study, laser peening was performed in a high-vacuum environment using silicone rubber (polydimethylsiloxane) as the plasma confinement layer. It is softer and conforms to the shape of metal in a vacuum environment. Through experiments, the appropriate process window for laser irradiation was explored by varying the intensity and number of laser shots.