Characterization of microstructure, local deformation and microchemistry in Alloy 600 heat-affected zone and stress corrosion cracking in high temperature water

With increasing the distance from the weld fusion line in an Alloy 600 heat-affected zone, kernel average misorientation decreases and the fraction of Σ3 boundaries increases. Cr7C3 carbides mainly precipitate at random high angle boundaries. Chromium depletion and segregation of boron and phosphorous at grain boundaries are observed. Alloy 600 heat-affected zone specimens exhibit higher intergranular stress corrosion cracking growth rates than that in the base metal in simulated pressurized water reactor water environments. Crack growth rate is enhanced by strain hardening and by increasing temperature. The role of stress on interface oxidation kinetics is analyzed.

► Away from fusion line in Alloy 600 HAZ, the fraction of Σ3 boundaries increases and KAM decreases.
► Cr7C3 carbides mainly precipitate at random high angle boundaries.
► Chromium depletion and segregations of boron and phosphorous at grain boundaries.
► High PWSCC growth rates in Alloy 600 heat-affected zone than that in the base metal.
► The effect of stress on interface oxidation kinetics is quantified.