Product Code: ICAL08_P138

Experimental Investigation of Laser Shock Peening for a Zinc-Coated Low Carbon Steel Using Femtosecond Laser Pulses
Authors:
Dongkyun Lee, The University of Michigan; Ann Arbor MI USA
Elijah Kannatey-Asibu Jr, The University of Michigan; Ann Arbor MI USA
Presented at ICALEO 2008

In this study, the feasibility of laser shock peening using ultrafast laser pulses was experimentally investigated. A top coating of zinc with a water confining layer was applied in the investigation. The zinc coating was used for the thermo-protective effect, and also for in-situ investigation on the feasibility of laser microwelding using femtosecond laser pulses. A high numerical aperture aspheric lens was used to minimize the optical breakdown of water. Microhardness measurements were made on the top surface of the shock peened specimen and compared with the original material hardness.
The results indicate that fluence has significant effect on microhardness of galvanized steel measured on the top surface, which is mainly due to removal of the top coating. Improvement in microhardness of base steel after the experiment was slight, compared to results for long pulse lasers in the literature. This indicates that the femtosecond laser may not be a good tool for laser shock peening, for the conditions used in this study. The results do not completely exclude the potential for improving laser shock peening using femtosecond laser pulses. However, it is questionable whether laser shock peening with femtosecond pulse duration may produce feasible results without increasing the pulse duration.