Cracking characteristics of A516 steel weldment in H₂S containing environments

Sulfide stress cracking (SSC) and hydrogen-induced cracking (HIC) are two well-known phenomena that take place in steels situated in H₂S containing environments. This investigation presents the cracking characteristics of A516 pressure vessel steel weldments prepared by submerged arc welding, under various welding heat inputs (15, 30 and 45 kJ cm^-1), following immersion in NACE TM-01-77 solution (5 wt.% NaCl + 0.5 wt.% CH₃COOH) saturated with H₂S gas. The results of slow strain rate testing, performed at a strain rate of 5 × 10^-7 s^-1, reveal the presence of SSC, HIC, and quasi-cleavage fracture in the base metal. Metallographic examination of the fractured specimens reveals that HIC initiates and/or propagates in both the ferrite and pearlite phases and along the ferrite/pearlite interface in the base metal. An increase in the welding heat input causes increases in the amount of grain boundary ferrite and Widmanstätten ferrite in the weld metal and heat-affected zone (HAZ), respectively, and subsequently results in decreases in the cracking resistances of the weld metal and HAZ n H₂S containing environments.