Investigation on femto-second laser irradiation assisted shock peening of medium carbon (0.4% C) steel

Abstract

In the present study, the effect of femtosecond laser irradiation on the peening behavior of 0.4% C steel has been evaluated. Laser irradiation has been conducted with a 100μJ and 300fs laser with multiple pulses under varied energy. Followed by laser irradiation, a detailed characterization of the processed zone was undertaken by scanning electron microscopy, and X-ray diffraction technique. Finally, the residual stress distribution, microhardness and wear resistance properties of the processed zone were also evaluated. Laser processing leads to shock peening associated with plasma formation and its expansion, formation of martensite and ferrito–pearlitic phase in the microstructure. Due to laser processing, there is introduction of residual stress on the surface which varies from high tensile (140MPa) to compressive (−335MPa) as compared to 152MPa of the substrate. There is a significant increase in microhardness to 350–500VHN as compared to 250VHN of substrate. The fretting wear behavior against hardened steel ball shows a significant reduction in wear depth due to laser processing. Finally, a conclusion of the mechanism of wear has been established.