Microstructual Study of the Dissimilar Joints of Alloy 690 and SUS 304L Stainless Steel

This study was to characterize the microstructure of Alloy 690-SUS 304L stainless steel dissimilar weldments with Inconel 52 and 82 filler metals (I-52 and I-82). The weldments were butt-welded with gas tungsten arc welding. Microstructural analyses were conducted on the samples prepared from the middle of each fusion zone. Precipitates observed in the interdendritic region and along the grain boundary of the I-52 fusion zone were TiNs, while Ti-Nb-rich phases were detected in the I-82 fusion zone. In the root regions, Cr-carbides precipitated abundantly in the I-52, whereas few Cr-carbides were found in the I-82. The Cr content of the grain boundary was higher than 9 mass% in the root regions of both I-52 and I-82 welds. Owing to the dilution with base metal Alloy 690, the average Cr content was higher in the I-82 root region than in the cap region.