Analysis on micro-mechanic field at SCC tip in the high hardness zone of a dissimilar weld joint

Lingyan Zhao, He Xue and Fuqia

Abstract

Dissimilar weld joints in the safe end of nuclear pressure vessels are more susceptible to stress corrosion cracking (SCC). Microstructure and material property in the nickel-based alloy weld especially the high hardness zone (HHZ) are quite complicated and different from the bulk material, which make it more susceptible to SCC. To clarify the effect of sampling location on SCC driving force of an Alloy 182-A533B dissimilar weld joint, an inhomogeneous mechanical property model is established, the micro-mechanic fields at SCC tips in the HHZ with different sampling location are analyzed. The results indicate that the micro-mechanic field is obviously influenced by the material property of the HHZ. The equivalent plastic strain ahead of crack tip may be a more effective mechanical parameter in describing mechanical state close to the SCC tip. The crack growing will be retardant when the crack in Alloy 182 weld propagates from the dilution zone (DZ) towards low alloy steel (LAS). The yield stress jump in the HHZ will lead to a decreased crack growth rate.