Effect of laser peening without coating on mechanical and microstructural behaviour of SS 304 stainless steel

Abstract

This present work investigates the influence of laser shock peening without coating (LPwC) of SS 304 stainless steel. To understand the effect of deformation behaviour, laser power densities of 3, 6 and 9 GW cm−2 were employed. The Residual stress and microhardness (HV) were investigated at surface and depth direction. The maximal value of compressive residual stress (−340 MPa) reached a depth of 50 µm for the laser intensity of 9 GW cm−2. Micro hardness significantly increased to 71.11% for 9 GW.cm−2 compared to the unpeened sample. To observe the mechanical twinning and grain refinement the Electron backscattered diffraction (EBSD) was carried out. A Transmission electron microscope (TEM) was also performed to know the nano twins and dislocation movement in the laser peened samples. Results showed that laser peening without coating process would cause a significant improvement on surface properties such as compressive residual stress, surface roughness, microhardness, and microstructure and grain refinement.