Femtosecond Laser Peening of Stainless Steel

We demonstrate the femtosecond laser peening, which has not been reported thus far, of stainless steel. The test sample used in the present study is commercial SUS304 stainless steel. The sample is investigated under femtosecond laser-shock loading in a plasma confined by water at the highest intensity of 56 TW/cm(2). The Vickers microhardness test is used to probe the residual stress and strain hardening caused by laser peening. The hardness of laser-peened SUS304 increases with an increase in the laser intensity and number of laser shots irradiated per unit area. A femtosecond laser has the potential to improve the mechanical performance of stainless steel under extremely low energy irradiation of the order of several hundreds of microjoules.