Effects of Yttrium on the pitting corrosion behavior of 304 stainless steel with coating by laser remelting

Abstract

The remelted layers with or without Y2O3 were prepared for 304 stainless steel (SS) by laser remelting for improving the pitting corrosion resistance. Influences of laser remelting and Y2O3 addition on the microstructure and the pitting corrosion behavior of 304 SS have been investigated. The pitting corrosion resistance of 304 SS can be improved by laser remelting because of the fine grains were formed within the remelted layer of 304 SS after laser remelting. The addition of Y2O3 can effectively refine the grain size and eliminate the defects and inclusions in the remelted layer. The microstructure of the remelted layer was more uniform and compact that can hinder the contact between the aggressive media and the matrix. In this study, the pitting potentials of remelted layer with or without addition of Y2O3 were 0.20 V and 0.16 V respectively, which were both increased than that of the matrix (0.08 V). The polarization resistances of remelted layer with or without the addition of Y2O3 were 38 kΩ and 29 kΩ respectively, which were both increased than that of the matrix (23 kΩ). The addition of Y2O3 in laser remelting layer can obviously improve the pitting corrosion of 304 SS and the related mechanisms are also discussed.