Reducing the pitting susceptibility of AISI 304 stainless steel using a hybrid treatment of high-power diode laser and large pulsed electron beam irradiation

Abstract

Large pulsed electron beam (LPEB) irradiation has been widely used for surface modification of metals, alloys, polymers, and composites due to its unique interaction mechanisms with materials. The rapid melting and resolidification processes during LPEB irradiation induce phase transformation at the resolidified layer, which enables a simultaneous improvement in mechanical characteristics and chemical stability of metals. However, the generation of craters during LPEB irradiation adversely affects surface quality. It is imperative to minimize crater formation following LPEB irradiation to mitigate pitting corrosion on the surface of stainless steel (SS). In this study, a hybrid surface modification approach using a high-power diode laser (HPDL) and LPEB is proposed to reduce the crater generation during LPEB irradiation. The size and density of craters generated during LPEB irradiation were effectively reduced following the HPDL-LPEB irradiation hybrid surface treatment. The decrease in extent of crater formation and phase transformation has enabled an improvement in corrosion resistance. The ability of the resolidified layer formed after the hybrid HPDL-LPEB irradiation to form a stable passive film shifts the pitting potential from less than 0 mV/SCE (for untreated 304 SS) to more than +800 mV/SCE, which reduced the depth of corroded pits by 75%. The hybrid HPDL-LPEB irradiation decreased non-metallic inclusions, extent of crater formation and the surface roughness, and improved the pitting corrosion and general corrosion resistance.