Laser Shot Peening of 304 Austenitic Stainless Steel without Protective Coating

Laser Shot Peening without protective Coating (LPPC) was performed on SS304 austenitic stainless steel using a 300 mJ, 10 ns pulse, 1064 nm wavelength Nd:YAG laser with three different pulse densities. A thin layer of water was used as a confinement layer. The peened specimen was characterised with XRD, AFM and a Profilometer. The stress evaluated at the surface of the laser peened sample shows a maximum compressive stress of 1.6 GPa. The surface roughness and depth profile of microhardness before and after LPPC were investigated.The LPPC region indicate substantial improvement in microhardness and compressive residual stress, with marginal increase of surface roughness.