Hydrogen-induced cracking along the fusion boundary of dissimilar metal welds

Presented here are the results from a series of experiments in which dissim ilar metal welds were made using the gas tungsten are welding process with pure argon or argon-6% hydrogen shielding gas. The objective was to determi ne if cracking near the fusion boundary of dissimilar metal welds could be caused by hydrogen absorbed during welding and to characterize the microstr uctures in which cracking occurred. Welds consisted of ER308 and ER309LSi a ustenitic stainless steel and ERNiCr-3 nickel-based filler metals deposited on A36 steel base metal. Cracking was observed in welds made with all thre e filler metals. A ferrofluid color metallography technique revealed that c racking was confined to regions in the weld metal containing martensite. Mi crohardness indentations indicated that martensitic regions in which cracki ng occurred had hardness values from 400 to 550 HV. Cracks did not extend i nto bulk weld metal with hardness less than 350 HV. Martensite formed near the fusion boundary in all three filler metals due to regions of locally in creased base metal dilution.