Corrosion Enhancement of the AISI 304 Stainless Steel Using a High Power Diode Laser and Large Pulsed Electron Beam

Abstract

The large pulsed electron beam (LPEB) has been widely used for surface modification of metals, alloys, polymers and composites due to its unique interaction mechanisms with materials. Especially for metals, it can simultaneously improve mechanical characteristics and chemical stabilities during rapid melting and re-solidification processes inducing a phase transformation at the re-solidified layer. However, generation of craters has been reported to adversely affect surface quality. It is important to reduce the craters following the LPEB irradiation for the effective protection of pitting corrosion on the surface of stainless steels. In this study, a hybrid surface modification method using a high power diode laser (HPDL) and LPEB is proposed to reduce the generation of craters during the LPEB irradiations. The size and density of craters generated during the LPEB irradiations were effectively reduced following the hybrid surface treatment using HPDL. The corrosion resistance was significantly improved by reducing craters and phase transformation. The passive region on the re-solidified layer after the HPDL-assisted LPEB irradiation showed much wider range comparing to the bare surface of stainless steels. Furthermore, the pitting potential was also significantly modified from less than 0 mV/SCE to over 800 mV/SCE following the hybrid irradiations. After the corrosion tests, the depth of corroded pits was also significantly reduced by 75 % after the hybrid surface modification. To conclude, the HPDL-assisted LPEB irradiation has resulted in superior surface profile and improved pitting corrosion resistance as well as the general corrosion resistance following the elimination of non-metallic inclusions on the surface.