A Study on the Pitting Initiation of Duplex Stainless Steel (DSS 2205) Welded Joints Using SEM–EDS, SKPFM and Electrochemistry Methods

摘要

The influence of laser beam welding and a subsequent short-time post-weld heat treatment on thepitting corrosion in duplex stainless steel was investigated by diverse techniques, including thepolarization curve method, scanning electron microscopy–energy dispersive spectroscopy, scanningKelvin probe force microscopy and optical microscopy. It was found that for as-welded specimens, thefused zone was the preferential pit initiation site. The Volta potential maps for the laser beam weldedsamples revealed that some low potential areas emerged inside the ferrite phases, which may beconsidered as preferential nucleation sites for the pitting corrosion. The pit morphologies showed thatthe pits were generated in areas with a lower surface potential value. After a 3 min post-weld heattreatment at 1080?C, the reduction in the surface potential differences indicated that the corrosionresistance of laser welded joints was restored, and the low potential areas that indicated the chromiumdepleted regions around the Cr2N disappeared.