Laserpeening

Laser peening is a surface treatment that enhances the fatigue strength and damage tolerance of metallic components by generating deep, compressive residual stresses beneath the surface through laser-induced shock waves. The process uses a high-energy pulsed laser directed at the material surface after applying an absorptive layer. When the laser pulse interacts with the surface, a small amount of material is ablated, forming a plasma. The rapid expansion drives a shock wave into the substrate, plastically deforming the near-surface region. As the surface relaxes, a residual compressive stress field remains, counteracting tensile stresses that occur during service.

Typical implementations employ Q-switched or pulsed fiber lasers, with pulse durations in the nanosecond range. The energy, spot size, and shielding or coating layers are selected to produce peak pressures in the gigapascal range, yielding compressive residual stresses reaching hundreds of megapascals to about a gigapascal near the surface. The depth of the stressed layer depends on material and process parameters, commonly extending from a few tenths of a millimeter to about one to a couple millimeters.

Materials commonly treated include steels, stainless steels, aluminum alloys, titanium alloys, and nickel-based superalloys. Applications span aerospace components such as turbine disks and blades, gears and shafts, power-generation parts, automotive fasteners, and other critical load-bearing parts where fatigue life is a major concern. Process options include full-coverage peening or selective masking to accommodate complex geometries and tight tolerances.

Benefits of laser peening include significant improvements in fatigue life and resistance to crack initiation and propagation, as well as enhanced resistance to certain forms of stress corrosion cracking. Limitations include high equipment and operating costs, the need for specialized process control and safety measures, and potential surface finish considerations that require post-treatment planning.