FLASP – Fibered LASER Shock Peening

Aim: Fatigue life improvement of critical components by focusing on Fibered LASER Shock Peening (FLASP) that permits more flexibility and versatility than standard LSP because of the deporting of the laser beam thanks to an optical fiber.

Challenges: Laser shock peening (LSP) has been proven for many years as alternative to traditional peening (shot peening, ultrasonic shot peening, rolling, rotary peening, needle peening…) for hardening of parts subject to mechanical stress, but its use in the industry is relatively limited due to the extreme cost and complexity of its implementation. Furthermore, areas with a very small radius and complex geometries are inaccessible with conventional shot peening, and not always the induced compressive stresses, beneficial for the fatigue, stress corrosion cracking, or corrosion fatigue resistance of parts, are high, deep, precise and homogeneous enough. To treat a part, either the part itself or the peening system has to move. However, it is often complex to disassemble, move and manipulate the part.

Benefits: Imagine Optic develops the Fibered LASER Shock Peening (FLASP) that permits more flexibility and versatility than standard LSP because of the deporting of the laser beam thanks to an optical fiber and can be also implemented in a robotized environment. The benefits of FLASP are: improving metal properties for fatigue lifetime and corrosion resistance, while competing with conventional peening with metal balls, and densifying material with high residual stress inside the deeper layers. The use of standard high-energy lasers conditioned to drive in an optical fiber brings the following advantages: record-breaking injected energies in the nanosecond regime inside an optical fiber being more safe than conventional LSP because of no free-space lasers; fewer maintenance operations on the system as galvanometric mirrors are replaced by passive optical components and fiber; possibility to address wider surfaces on the parts to be treated thanks to long fibers (tens of meters); possibility to laser-process parts manually with a miniaturized optical head manipulated by certified personnel; consumable-free process (ecological); possibility of working on immersed parts to capture volatile micro-projections; accessibility in highly constrained areas such as nuclear irradiated zones; possibility of treating areas with a very small radius; easier and cheaper implementation compared to traditional peening.

Activities & Present achievements: The approach is to test and characterize the performance of fibered LSP on samples, then on parts of industrial interest (turbine blades for example). The tests will be carried out at Alphanov, which has an experienced team in industrial laser processes and a robotic enclosure dedicated to the LSP. The use of a robot will make it possible to perfectly master the tests on the part and to test the endurance of the optical fiber. Europe Technologies, as expert and user of peening technologies, will be able to test on samples the efficacy of FLASP.

Current Status: Both Deliverables for technology development phase were completed on time and passed the acceptance criteria agreed. Market analysis of competition base and end customers have been identified. The system’s performances have been experimented at Imagine Optic by developing a customized laser peening prototype platform. Such a platform helped Imagine Optic perform laser peening treatments on simple geometry parts made of materials of interest (aluminum, steel and titanium). These tests have shown good performances in terms of treatment depth as Europe Technologies residual stress measurements could detect compressive residual stress up to a depth of 1mm below the surface. Better surface roughness was also achieved with respect to the performances that are usually obtained by the conventional shot peening process. Such performances allowed the development of a compact optical head that will be focusing the laser beam on the parts to be treated during the next step of the project. Further experiments will be carried out at our subcontracting facility, Alphanov, in the next weeks. This new facility will help the project step up as it will make it possible to treat complex geometry parts thanks to a robotized arm, thus, giving the process a more industrial touch. These tests will be of great contribution to assess the positive effect of the FLASP treatment on complex geometry parts such as gears, blades or weld beads.