Influence of laser surface melting on the susceptibility to intergranular corrosion of sensitized Alloy 600

Abstract

The effects of laser surface melting (LSM) on the intergranular corrosion of the sensitized Alloy 600 were studied by the double loop electrochemical potentiokinetic reactivation (DL-EPR) method in de-aerated 0.01 M H2SO4 + 20 ppm KSCN at a scan rate of 0.5 mV/s at room temperature. The degree of sensitization (DOS) of the sensitized Alloy 600 measured from the DL-EPR test was considerably reduced by LSM, and the sensitized Alloy 600 after LSM also exhibited a relatively low DOS, comparing with that of the sensitized but not laser treated Alloy 600. From the microscopic examination, it was found that the microstructural changes induced by the laser treatment, especially changes in the precipitation behavior of grain boundary Cr-rich carbides, caused the improvement in resistance to intergranular corrosion of the laser treated Alloy 600. The resistance to intergranular stress corrosion cracking of the laser treated Alloy 600 in sulfur-bearing environments was also discussed from the results of measured DOS and microstructural examination. (C) 2001 Published by Elsevier Science Ltd .