Abstract
Effect of rapid solidification by laser surface melting on pitting corrosion resistance in weld metals of Mo containing stainless steels was investigated. Pitting corrosion resistance was evaluated through the pitting potential and the density of pits after FeCl3 solution immersion test. The pitting resistance in the weld metal was shown to deteriorate severely in comparison with that in the base metal, whereas, with laser melting treatment, to be improved to about the same level or slightly better than that of the base metal. SEM observation revealed that pits which had preferencially formed at the core of the solidification cell in the weld metal, had reduced in number and also in size after laser treatment. The element distribution across the solidification cell was found to become more even in the laser treated weld metal than non-treated one. On the basis of the results, the improvement of pitting corrosion resistance in the weld metal by laser treatment was considered to be attributed to the alleviation of the segregation due to the rapid solidification effect which caused the increase of Mo and Cr contents at the cell core, resulting in the enhancement of its corrosion resistance.
