Correlation of imposed mechanical energy with ductility-dip cracking in a highly restrained weld of Alloy 52

Abstract

Ductility-dip cracking (DDC) is a complex weldability issue affecting industries using high-chromium nickel-based filler metals required for superior resistance to stress corrosion cracking, most notably in the nuclear power generation industry. DDC is a solid-state cracking mechanism which occurs in the temperature range of 0.5–0.8TM and is primarily attributed to grain boundary sliding. Above 0.8TM, recrystallization inhibits initiation of DDC and has been observed to arrest propagation. A computational model of thermo-mechanical behavior in a narrow groove multipass weld of DDC-susceptible filler metal was developed in past research and revisited here to calculate and analyze the mechanical energy imposed during the welding process. It was found that areas in the weld with high imposed mechanical energy (IME) in the recrystallization temperature range coincided with regions devoid of cracking but rich in evidence of recrystallization. Weld areas with low IME in the recrystallization temperature range but with higher IME in lower temperature ranges coincided with regions where DDC is observed. This agrees with past research suggesting recrystallization acts to prevent cracking. This paper presents an integrated computational materials engineering (ICME) approach that includes the IME to better predict and quantify DDC susceptibility in multipass welds.