| Abstract Scope |
ASME Case N-888-1, “Similar and Dissimilar Metal Welding Using Ambient Temperature SMAW and Machine GTAW Temper Bead Technique,” requires a 48-hour wait period before the final nondestructive evaluation (NDE) is performed when ferritic filler metal is used. The 48-hour hold at room temperature is done to confirm the absence of delayed hydrogen-induced cracking (HIC) in the temper bead heat-affected zone. In previous research, the effect of post-weld heat treatment (PWHT) and temper bead welding (TBW) on the HIC susceptibility in the coarse-grained heat-affected zone (CGHAZ) of SA-508, P-No. 3 Group 3, pressure vessel steel was studied using the Delayed Hydrogen Cracking Test (DHCT). The Gleeble™ 3800 thermomechanical simulator was used to generate six CGHAZ microstructural conditions: as-welded (AW), PWHT, and TBW single reheats at 675, 700, 725, and 735°C. Dissociated hydrogen was introduced to the specimens through cathodic charging under in-situ constant tensile stress. The HIC susceptibility ranking by the DHCT is at diffusible hydrogen levels significantly higher than typical GTAW and SMAW processes. This paper extends the investigation on the susceptibility to HIC of these same CGHAZ microstructures by repeating the previous testing under different charging current densities to achieve diffusible hydrogen levels more representative of typical welding conditions. The aim is to establish the diffusible hydrogen threshold for onset of HIC. Fracture surface examination using scanning electron microscopy (SEM), optical cross-section microstructure examination, and hydrogen content measurements using gas chromatography will be performed to characterize the HIC susceptibility. The results from this project will be used to support elimination of the NDE hold time requirement in Case N-888-1 when ferritic weld metal is used. |