Effects of filler metal composition on joining properties of alloy 690 weldments

This work investigates the influence of filler metal composition on the corrosion resistance and mechanical properties of alloy 690 weldments. Alloy 690 (61 wt.% Ni, 30 wt.% Cr) was used as the base metal. Inconel I-52 (61 wt.% Ni, 29 wt.% Cr) and I-82 (73 wt.% Ni, 20 wt.% Cr) rods were used as filler metals. Manual gas tungsten arc welding was performed using four weld passes in three layers for a single-V groove butt weld. The subgrain structure near the centerline of the fusion zone middle layer was cellular and columnar dendritic in the I-52 weld, but was dominantly equiaxed dendritic in the I-82 weld. Both had white particles dispersed in the fusion zone. The I-82 weld had more white particles and a denser subgrain structure. Compositional analysis showed the I-52 weld's interdendritic region had higher Al, Si, Ti, N content than the dendritic core. The I-82 weld's interdendritic region had higher Al, Si, and Nb content than the dendritic core. The Ni and Cr content of interdendritic white particles of the I-52 and I-82 welds decreased to 38, 23 wt.% and 11, 9 wt.%, respectively, much lower than the base and filler metals. This situation causes high corrosion at the white particle sites during Modified Huey testing. Thus, the I-52 weld had better corrosive resistance than the I-82 weld. However, I-82's superior weld joint strength is attributed to its finer fusion zones subgrain structure and giving it higher tensile strength and elongation.